Watershed Planning and Management PDF

Watershed Planning and Management Module 1: Watershed Management – Problems and Prospects Lesson 1 Watershed and Its Management 1.1 Concept and Definition of Watershed The word ‗watershed‘ has different meanings. In British English it means a ridge line or a line wh...

Watershed Planning and Management Module 1: Watershed Management – Problems and Prospects Lesson 1 Watershed and Its Management 1.1 Concept and Definition of Watershed The word ‗watershed‘ has different meanings. In British English it means a ridge line or a line which shows slopes in two different directions on its either sides. A ridge line is also a line connecting the points of highest elevation in a terrain. Therefore, ridge line is also known as ‗watershed line‘ or a ‗surface water divide‘. In colloquial language the word ‗watershed‘ is used to describe a path breaking event. In American English, the word ‗watershed‘ is used as a synonym for ‗catchment‘ or ‗basin‘ wherein rainwater or storm water gets collected from an area enclosed by a ridge line. This water eventually flows through the various drainage channels which merge with one another to form one or rarely more than one outfall(s) of a stream. Thus, ‗watershed‘ is defined as an area enclosed within a watershed line. In this course, the word ‗watershed‘ is used for a small basin or a small catchment representing a hydrological unit which drains all its rainwater into a stream. Therefore, it is independent in terms of its water in general and surface water in particular. To distinguish a watershed -which generally implies a small catchment or a basin, Bali (1980) suggested an upper area limit of 2,000 km2 for a watershed. This classification is an extension of the classification suggested by Rao (1975) for large river basins -with an area greater than 20,000 km2, medium river basins –with an area between 2,000 and 20,000 km2 and small river basins commonly referred to as watersheds. Bali‘s classification of watersheds was probably reflected in the watershed classification by the All India Soil and Land Use Survey (AISLUS) in 1990. According to this classification, watersheds are further classified into 5 categories based on their areas as ‗macro-watersheds - with area between 500 and 2,000 km2, ‗sub-watersheds‘ –with area between 100 and 500 km2, ‗milli-watersheds‘ –with area between 10 and 100 km2, ‗mini-watersheds‘ –with area between 1 and 10 km2 as well as ‗micro- watersheds‘ –with area less than 1 km2. A watershed is a physical entity consisting of the natural elements in it such as plants of various sizes and types which grow over various types of soil or rock layers. Additionally, watershed also comprises of all the artificial elements such as roads, bridges, tunnels, buildings, and burrow holes etc. which are mostly introduced in it by human beings and sometimes by other animals. In the next section, we shall discuss about the scope of watershed management. 1.2 Scope of Watershed Management As we have already seen in the previous section, watersheds represent small basins. By delineating the ridgelines in a medium or a large river basin, the entire basin can be subdivided into a number of 5 www.AgriMoon.Com Watershed Planning and Management watersheds, each with an area within 2,000 km2. Because of their compact size, it is always easier to manage watersheds rather than a river basin. In a well-managed watershed, all the natural resources such as soil, water, vegetation, etc. are conserved. Vegetation or plants play a vital role in conserving the natural resources of a watershed such as soil and water. The underground components of the plants such as roots spread within the soil and thereby stabilize and reinforce the soil. This generally leads to soil conservation. The water infiltrates below the ground through the voids in the soil as well as through the interface between the root surface and the soil. The terrestrial components of plants such as stems, branches and leaves prevent the soil below it from getting directly exposed to sunlight as well as to the impact of raindrops. Thus, a significant part of the momentum and energy in rainwater is absorbed and thereby inducing/ accelerating the downward movement of rainwater through stem flow and infiltration. On one hand this process creates water bodies like the groundwater reservoirs and rivers, which are good sources of water and nutrients required for plant growth. On the other hand, this process also substantially reduces the soil erosion and the surface flow velocity of storm water. Additionally, there will be release of ample amount of oxygen, generation of colorful and fragrant flowers, fresh leaves as well as fruits through the process of photosynthesis. This makes the entire watershed very pleasant for human beings, migratory birds, flying insects as well as all other animals. The fruits and leaves also serve as food for human beings and animals. A watershed containing large amounts of vegetation is considered as a healthy watershed. It is also called a well-managed or a ‗green watershed‘. It has no or very limited soil erosion and also it has large reserves of groundwater as well as surface water. In general, it has most of its natural resources conserved. Thus, the scope of watershed management involves all the actions and programs aimed at achieving an overall balance between utilization and conservation of natural resources in a watershed. It represents a sustainable approach for resource conservation through watershed management. In the next section, the Indian and global perspective to watershed management is discussed. 1.3 Watershed Management: Indian and Global Perspective India has the second highest population of over 1.2 billion among all the nations [i.e., 17.1% of the world population], a seventh highest land area of 3.29 million km2 among all the nations [i.e., 2.4% of the world area] and an annual river flow of 1869 km3 out of an annual rainfall of about 4000 km3 [i.e., 4% of the world water]. The rainfall distribution is highly uneven spatially with the highest annual rainfall of 11,690 mm in the north-eastern state of Meghalaya and the least annual rainfall of 150 mm in the western part of the north-western state of Rajasthan. The number of rainy days [i.e., number of days with a minimum recorded daily rainfall of 2.5 mm] varies from 5 to 150. The rainfall distribution is also very uneven temporally with about 75% of the annual rainfall occurring only in the four monsoon months of June to September. The average annual rainfall is 1160 mm which is slightly higher than the global average of 1110 mm. In the year 2010, the annual per capita water availability was estimated at 1588 m3, which is considered as water stressed [i.e., between 1,000 and 1,700 m3] as per the international norms. The per capita water availability was 5200 m3 during the year 1951. The annual potential evapo-transpiration (PET) varies from 1,500 to 3,500 mm. 6 www.AgriMoon.Com Watershed Planning and Management Although India has a well-developed precipitation pattern in the form of monsoons and an equally well developed drainage network consisting of 14 large river basins, 44 medium river basins and hundreds of small river basins, there is a huge stress on water and land resources due to continuous overexploitation. This has led to many adverse hydro-meteorological impacts like large scale soil erosion, excessive lowering of water table, extensive river/ ground water pollution due to municipal/industrial wastewaters, widespread loss of forests/ grass lands/ crop lands/ wetlands/ water bodies, silting of existing water bodies, frequent occurrence of floods/ droughts, alarming reduction in Himalayan glaciers etc. All these phenomena have generally made the Indian perspective in watershed management very vulnerable to climatic and anthropogenic factors. Thus, achieving sustainable water resources development and integrated watershed management are two major challenges in the Indian context. In spite of this alarming scenario, there are hundreds of best management practices (BMPs) –adopted both in the government sector and the non-government sector over the entire length and breadth of India, which have been the bright spots in water and land resources management. These BMPs employ technologies which are either traditional or modern or a combination of both. Some of these BMPs -which were effectively implemented in different parts of India, are as follows: 1) An effective implementation of the ban on tree cutting policy by the local government authorities in the north-eastern state of Sikkim resulted in an increase in the forest cover from 44% in 1995-‘96 to 47.59% in 2009 [Hindustan Times, 2010]. 2) During 2000 to 2006, voluntary work by hundreds of people led by a spiritual saint near Jalandhar in the north Indian state of Punjab, resulted in the near total cleaning and rejuvenation of 35 km of Kali Bein River, which was heavily polluted by industrial effluents and garbage [The Times of India, 2007]. 3) Over a 20-year period starting from 1974, a severely drought prone village of Ralegan Siddhi in the western Indian state of Maharashtra –even with an annual rainfall of about 200 mm, had transformed into a village with ample drinking water, food and fodder. This was possible due to the adoption of ridge to valley approach in watershed management through social forestry, grassland development, continuous contour trenching, loose boulder structures, brushwood dams, nulla bunds, percolation tanks, underground dams, gabion bunds, check dams, farm ponds, staggered trenches for arresting soil erosion and ban on free grazing [Hazare, 1994]. Global perspective on watershed management is having many similarities and some differences with the Indian perspective. Moreover, there are even bigger spatial and temporal variations in water/ pollutant distribution. It is also very much affected by soil erosion, excessive lowering of water table, extensive river/ ground water pollution due to municipal/industrial wastewaters, widespread loss of forests/ grass lands/ crop lands/ wetlands/ water bodies, silting of existing water bodies, frequent occurrence of floods/ droughts, alarming reduction in glaciers etc. These phenomena have resulted in major constraints due to water scarcity and land scarcity. However, in majority of the developed world and in many parts of the developing world, sufficient watershed management activities have been initiated in the government and non-governmental sectors. 7 www.AgriMoon.Com Watershed Planning and Management The impact of these watershed management programs is varied ranging from failures with undesirable environmental and socio-economic consequences to significant benefits. To make the watershed management programs sustainable, land and water resources need to be managed together with an interdisciplinary approach. There is also a strong need to develop regional training and networking programs at all levels, especially when government agencies are not fulfilling their role in watershed management. The emergence of citizen-based watershed organizations in the United States and many other countries is a very positive development. 1.4 Timeline of Watershed Management Programmes in India The watershed management concept in India starts from the pre-historic times. In the Shanti Mantra or the peace hymn of Yajur Veda –one of the four Vedas or treatises of knowledge in the ancient Indian philosophy –which is written/ codified in Sanskrit, there is a phrase which states that ‗…..prithivih shantih aapah shantir oshadhayah shantih…‘. The meaning of this phrase is ‗…let there be peace on earth, water, vegetation…‘. This is possibly one of the oldest references to watershed management. Additionally -in that hymn, peace is also sought in heaven, sky, Gods and in all natural entities/ living organisms -starting with the person reciting this Mantra. The actual timeline of watershed management programmes in India starts from the 1950s during the First Five Year Plan, with the establishment of a number of Soil Conservation Research Demonstration and Training Centres (SCRDTCs) by the Ministry of Agriculture (MoA) of the Government of India (GoI). In 1956, 42 small [i.e., less than 1 km2] experimental watersheds were established for monitoring the impact of land use changes and conservation measures on surface hydrology, soil loss reduction and biomass productivity improvement. In 1961-‘62, the MoA, GoI sponsored a scheme for soil conservation in the catchments of River Valley Projects (RVPs) for preventing siltation in major reservoirs. In 1974, all the SCRDTCs were reorganized under the Central Soil and Water Conservation Research and Training Institute (CSWCRTI), Dehradun. A real breakthrough was achieved by CSWCRTI when watershed technologies were demonstrated under natural field settings using community driven approaches through four model Operational Research Projects (ORPs) in different regions of the country. The world famous Sukhomajri model in Haryana was also one of them. The Ministry of Rural Development (MoRD), GoI launched major nationwide watershed development programs like the Drought Prone Area Programme (DPAP) in 1973-‘74 and Desert Development Programme (DDP) in 1977-‘78. The MoA, GoI launched watershed programs in 10 catchments under the Flood Prone Rivers (FRP) Project. During 1983, encouraged by the success in the earlier four model ORPs, CSWCRTI, Dehradun developed 47 model watersheds in the country in association with the Central Research Institute for Dryland Agriculture (CRIDA), Hyderabad. MoRD, GoI also started adopting watershed approach in 1987. The Planning Commission, GoI also started adopting integrated watershed approach in 1987- ‘88 for its Western Ghats Development Programme (WGDP) and Hill Area Development Programme (HADP) covering 16,000 km2 area in Maharashtra, Goa, Karnataka, Kerala and Tamil Nadu. In 1989- ‘90, the Ministry of environment and Forests (MoEF) initiated National Afforestation and Eco- development Projects (NAEP) scheme following integrated watershed approach. 8 www.AgriMoon.Com Watershed Planning and Management In the 1990s, many watershed development programs externally funded by the World Bank, European Economic council (EEC), Danish International Development agency (DANIDA), some Indo-German, Indo-Swiss and Japanese organizations were undertaken in various parts of India. Around the same time, MoA initiated a massive project on National Watershed Development Programme for Rainfed areas (NWDPRA) in 1991. In 1995, MoRD launched another big project called Integrated Wastelands Development Project (IWDP) with well formulated guidelines. In 2001, the Planning Commission, GoI drew up an ambitious plan of treating 88.5 Mha of degraded/ rainfed lands in India, by the end of the 13th Five Year Plan in 2022 involving a huge financial investment of Rs. 72,750 crores. To strengthen the participating institutes, MoRD revised the watershed development guidelines as ‗Haryali‘ [i.e., greenery] guidelines in 2003. The GoI established the National Rainfed Area Authority (NRAA) under the Planning Commission in 2006. MoA also started the projects on Reclamation of Alkali soils (RAS), Watershed Development Project for Shifting Cultivation Areas (WDPSCA), Indo-German Bilateral Project (IGBP) and World Bank assisted Sodic Land Reclamation Project (SLRP). MoRD has initiated watershed projects under Mahatma Gandhi National Rural employment Guarantee Act (MGNREGA), Investment Promotional Scheme (IPS) and Technology Development Extension and Training (TDET), Wastelands Development Task Force (WDTF). Till March 2005, an area of 28.53 Mha was treated at an investment of Rs. 1,457 crores by MoA, MoRD, MoEF, out of a total degraded land of 146.82 Mha –as per the estimates of the National Bureau of Soil Survey & Land Use Planning (NBSS&LUP), Nagpur. From 2008, the new watershed projects are being implemented as per the latest common guidelines for watershed development projects, developed by the NRAA. Keywords: River Basin, Watershed, Watershed management, Global watershed management perspective, Indian watershed management timeline 9 www.AgriMoon.Com Watershed Planning and Management Lesson 2 Problems and Prospects in Watershed Management Watershed management encounters many problems and constraints. Some of the major problems and constraints in watershed management are listed below. 2.1 Problems and Constraints in Watershed Management (a) Land degradation in rain fed areas due to soil erosion from runoff is one of the major problems. In India it was estimated that the soil erosion in the 1990s was almost double that of soil erosion in the 1980s. Rainfall uncertainty and poor economic conditions act as a major constraint and thus prevents the farmers in rainfed areas from making investments. This leads to improper watershed management. (b) Equitable benefit sharing of watershed management within the farming communities as well as within the different locations of watershed is a huge problem. Generally, women, marginal farmers and landless laborers gain very little or nothing at all from the watershed management activities. Several case studies in water scarce states of Gujarat and Madhya Pradesh in India have showed that overdevelopment of water harvesting structures in the upstream portion of watersheds had significantly reduced the inflows into the downstream reservoirs. On the other hand, it is also noticed that building of large reservoirs resulted in the submergence and hardship in the upstream parts and benefits for people in the downstream parts of the same watershed or a neighboring watershed generally having an urban or an industrial area. (c) Acute shortage of water in general and drinking water especially in summer has been observed in many watersheds with inadequate watershed management which may result in severe/ recurrent droughts. It may often result in limited and temporary food productivity gains. (d) Many a times, common lands do not get treated adequately and re-vegetation does not take place as expected in spite of the watershed management programs. As a result of this, domestic/ ecosystem water needs and livestock water/ fodder needs are either inadequately addressed or are made to suffer due to increased water withdrawals by other uses or due to overgrazing. (e) Problems exist or new problems crop up due to improper understanding of the interaction between biophysical and socio-economic processes in watershed management. (f) Conflict among various government ministries such as those related to agriculture [with emphasis on food production], rural development [with emphasis on employment generation & poverty alleviation], forests [with emphasis on maintaining biodiversity & wildlife], as well as conflict between government bureaucracy and elected representatives in their zeal to control funds, is a major problem in watershed management programs -which requires to be resolved on a priority basis. 10 www.AgriMoon.Com Watershed Planning and Management (g) It is hard to conduct meaningful impact assessment studies on watershed management programs for lack of baseline data for monitoring and comparison of the current conditions. The whole exercise of watershed management is undertaken without properly estimating the water supply scenarios under drought/ normal/ surplus years as well as without proper demand management especially during drought years. (h) Large areas inhabited with tribal population lack facilities to harvest water and to stabilize their food/ crop/ fodder production due to reduced forest yields, deterioration in land quality, lack of tribal agriculture policy and population pressure. This leads to a sustained misery, socio-political unrest and insurgency among the tribal population. 2.2 New Prospects and Opportunities Associated with Watershed Management In spite of the above-mentioned problems and constraints as well as some other problems and constraints, watershed management is associated with new prospects and opportunities. Some of them are listed below: (a) There is a need to produce more and better food without further undermining the environment/ ecology, especially the land, water, forests, wildlife and atmosphere. This may include adoption of best management practices (BMPs) such as organic farming, de-silting for reservoir capacity restoration as well as for crop productivity increase, sprinkler and/ or drip irrigation to avoid excess use of water, no tree felling policy, afforestation and arboriculture through high oxygen yielding & other medicinal plants etc. (b) There is a need to ensure that gains due to groundwater recharge are not dissipated by excess groundwater extraction. To achieve this, groundwater over-extraction should be avoided through public awareness and also through regulation. (c) There is a need to consider the downstream impacts of intensive upstream water conservation. For this, watershed associations with representations from all the stakeholders in the watershed should be made operational. These associations can take decisions in the best interest of all the people concerned. (d) Decreasing the costs at which the gains are achieved and thereby increasing the modest benefit- cost ratio should offer new prospect and opportunity in watershed management. To realize this, low cost technologies which may involve local materials, labour at practically no cost, technologies which are traditional and time tested should be employed to generate more benefits spread over the entire watershed among all the stakeholders. (e) Increasing all sections of people‘s participation beyond the project implementation stage to ensure sustainable watershed management should be a top priority. Only this can ensure progress on a sustained basis overcoming the hydro-geological, socio-political and other uncertainties. (f) Many successful watershed management programs -especially in India, have been implemented on a small scale in a few villages by collaborated efforts among the government departments, non- governmental organizations (NGOs) and research organizations. They represent sporadic BMPs. Hence there is a need to scale up the watershed management activities over large areas which could 11 www.AgriMoon.Com Watershed Planning and Management include remote and/or difficult terrains, so that many problems affecting our agricultural, rural and forest sectors can be effectively addressed. (g) Since there have been no or very few institutions built for research & development on collective management of watersheds, there is a need to build centers of advanced learning employing the modern tools of remote sensing, geographic information systems, decision support systems, computer based planning tools, poverty & socio-economic analysis etc. (h) There is a need to preserve and improve common pool resources (CPRs) of land, water, fodder, forest, fisheries, wild life and agriculture which significantly contribute towards people‘s livelihood especially in the rural areas. (i) There is a need to minimize migration to urban areas by creating opportunities in agriculture, natural disasters like floods/ droughts, forest/ mountain economies and by arresting fall in agricultural prices, gap in urban/ rural wages, gaps in urban/ rural employment opportunities. Keywords: Watershed management problems, watershed management constraints, watershed management prospects, watershed management opportunities. 12 www.AgriMoon.Com Watershed Planning and Management Module 2: Land Capability and Watershed Based Land Use Planning Lesson 3 Land Capability and its Classification Land capability plays a vital role in deciding the land use. In this lesson, we shall discuss on land capability and its classification. 3.1 Definition of Land Capability Land capability may be defined as the ability of the land surface to support natural plant growth/ wildlife habitat or artificial crop growth/ human habitat. Thus, it indicates the type of land use [viz., human habitation, agriculture, pastures, forests, wildlife habitat, etc.] that is suitable over a particular type of land. Different lands have different capabilities depending on the land characteristics like slope, soil type, soil depth and erosion conditions. If certain land characteristics are not conducive for agriculture, it is desirable to utilize or ensure the continuity of that land area for other land uses as mentioned earlier. The ultimate goal of allocation of various land capabilities over a vast land area with varied characteristics is to achieve complete soil conservation. Complete soil conservation implies perfect soil health and zero soil erosion on a sustained basis. It also facilitates total water conservation and total vegetation conservation. Thereby it results in integrated watershed management on a long term basis. In the next section, we shall discuss the classification of land capability based on the land characteristics. This land capability classification should ensure appropriate land use for every land area for peaceful coexistence of different flora and fauna including human habitation and also a sustained productivity through human activities. 3.2 Classification of Land Capability The Soil Conservation Service (SCS) of the United States Department of Agriculture (USDA) has done a pioneering work on land capability classification [Klingbiel and Montgomery, 1961]. According to that, the land capability is classified broadly into two groups based on the cultivability of the land. The first group consisting of all the lands which are suitable for cultivation is referred to as ‗Group 1 Lands‘. The remaining group consisting of all the lands which are unsuitable for cultivation is referred to as ‗Group 2 Lands‘. Each of these two groups are further classified into four classes. Thus ‗Group 1 Lands‘ comprise ‗Land Classes I to IV‘ which are cultivable and ‗Group 2 Lands‘ comprise ‗Land Classes V to VIII‘ which are non-cultivable. The following paragraphs describe each of the two groups and eight land classes in terms of their land characteristics and land use: 13 www.AgriMoon.Com Watershed Planning and Management Group 1 Lands: Generally Suitable for Cultivation Class I Lands: These lands are nearly level with slopes generally within 1%. The soils are deep, fertile, easily workable and are not subjected to damaging overflows. There are hardly any restrictions or limitations for their use. These lands are very good lands which can be safely cultivated by using any farming method to grow any crop, even intensively also. However, proper crop rotation and green manure use should be followed to maintain soil fertility [Mal, 1994]. Class II Lands: These lands generally have gentle slope in the range of 1 to 3%. They can be easily cultivated with some conservation practices like contour farming, strip cropping, bund construction or terracing. Therefore one or more of the following limitations exist which slightly reduce the crop choice [Murthy and Jha, 2011]: 1. Moderate susceptibility to erosion by wind or water; 2. Less than ideal soil depth; 3. Somewhat unfavourable soil structure and workability; 4. Slight to moderate salinity; 5. Occasionally damaging overflows; 6. Wetness existing permanently which can be corrected by drainage; and 7. Slight climatic limitations on land use and management. Class III Lands: These lands generally have slopes in the range of 3 to 5% and therefore have severe limitations which further reduce the crop choice or require special conservation practices [like contour farming, strip cropping, cover cropping, bund construction or terracing] or both. Lands in this class have more restrictions than those in Class II Lands due to land characteristics. All the limitations of Class II Lands are applicable here also, but to a greater extent. Hay or pasture crops that completely cover the soil should be preferred. On wet lands of this Class -which usually have heavy and slowly permeable soils, a drainage system along with a suitable cropping plan to improve the soil structure is required. Class IV Lands: These lands have fairly good soils [i. e., having shallow soil depth and low fertility] and generally have somewhat steep slopes in the range of 5 to 8%. Therefore they have either very severe limitations that largely restrict the crop choice or require very careful management or both. Lands may be suitable only for two to three common crops which build and maintain soil -like the fully covering pastures, with occasional grain crops which can be grown usually once in five years. These lands may have one or more of the following permanent features [Murthy and Jha, 2011]: 1. Heavy susceptibility for erosion due to wind, water with severe effects of past erosion; 2. Low moisture holding capacity; 3. Frequent overflows accompanied by severe crop damage; 14 www.AgriMoon.Com Watershed Planning and Management 4. Water logging, excessive wetness and severe salinity; and 5. Moderately adverse climate. Land Capability Sub-Classes: Lands in Classes II, III and IV are further categorised into sub-classes based on the following limitations: 1. Risk of erosion or past erosion damage is designated by the symbol ‗e‘; 2. Wetness damage or overflow is designated by the symbol ‗w‘; 3. Soil root zone limitations are denoted by ‗s‘; and 4. Climatic limitations are designated by ‗c‘. Group 2 Lands: Generally Not Suitable for Cultivation Class V Lands: These lands generally have slopes in the range of 8 to 12%. They usually have no to little erosion hazard but have other limitations which restrict their use mainly to pastures, forests, wildlife food and cover. Controlled grazing may be permitted. Some of the examples of Class V Lands are: 1. Bottom lands subject to frequent overflows that prevent the normal production of cultivated crops; 2. Stony or rocky lands; 3. Few ponded areas where soils are suitable for grasses or trees. Class VI Lands: The lands in this Class have shallow soils and generally have quite steep slopes ranging to 18%. They have severe limitations which restrict their use to pastures with very limited grazing, woodlands, wildlife food and cover. Some of the limitations of these lands which can‘t be corrected are: 1. Severe erosion; 2. Stony texture with shallow rocks 3. Excessive wetness or overflow 4. Low moisture capacity 5. Severe climate. Class VII Lands: The lands in this Class are generally eroded, rough, having shallow soil depth and steeper slopes ranging to 25%. The soils may be swampy or drought prone, with all the limitations of Class VI Lands even to a higher degree. If there is good rainfall, they may be used for forestry with fully green cover, gully control structures and severely restricted grazing. 15 www.AgriMoon.Com Watershed Planning and Management Class VIII Lands: These lands are rough with probably the worst soil types and possibly the steepest slopes in excess of 25%. They can only be used with very sound gully control measures for forests –if conducive for tree growth, and also for wildlife habitat. However, tree felling and grazing should be strictly avoided. Certain lands in Group 2 can be made cultivable with major earthmoving or other effective and costly reclamation operations. In India, both the Class VII Lands and Class VIII Lands are combined as Class VII Lands. Keywords: Land capability, land capability classification, Group 1 lands, Group 2 lands. 16 www.AgriMoon.Com Watershed Planning and Management Lesson 4 Watershed Based Land Use Planning In this lesson, we shall discuss the impact on watershed due to land use and spatio-temporal changes in it. Then we shall move on to the planning of land use to ensure a sustainable watershed. 4.1 Impact on Watershed due to Land Use Watershed and the land use are quite inter-dependent. Watersheds with a healthy aquatic system -in the form of adequate streams & wetlands, and an equally healthy biotic system -in the form of adequate flora and fauna, are generally sustainable systems. Once they are subjected to large scale human interventions and/ or natural calamities, the land use gets altered significantly. This in turn causes major impact in the watershed in terms of its hydrology, flora and fauna. In many parts of the world, extensive areas of native forests and grasslands have been converted into croplands or urban areas or road/ railway systems/ networks. This has resulted in the alteration of riparian corridors, drainage of wetlands and modification of natural river systems. These changes in the land use have resulted in the hydrologic changes in the watersheds, their stream systems and surface water-groundwater linkages. Changes in water quantity and quality can affect people and ecosystems in both upstream and downstream areas of watersheds [Brooks et al, 2013]. If these changes occurring in watersheds are not managed properly, they may become unsustainable in the long run. Therefore to avoid any undesirable consequences, increased attention is being paid to maintaining or restoring natural stream channel systems, riparian communities, wetland ecosystems and floodplains which can restore the good hydrologic conditions of watersheds. Thinking on these lines, Hey (2001) called for a major program to maximize the natural storage in the wetlands and floodplains as well as to minimize conveyance in the upper Mississippi River Basin. Such a program would effectively reverse some of the impacts of the past 200 years of levee construction and other engineering practices in the basin. If watersheds are not sustainably managed, they may show cumulative watershed effects i.e., combined environmental effects of activities in a watershed that can adversely impact beneficial uses of lands [Sidle, 2000]. Individually these environmental effects may not appear to be relevant. But collectively, they may become significant over time and space. For example, the conversion of forest to crop lands in one part of a watershed can cause an increase in the water and sediment flow. Likewise, road construction and drainage can also have effects in a watershed similar to drainage of a wetland at some other location. Similarly, removal of dense shrubs to increase forage production may also increase water yield in some cases, benefit certain wildlife species and reduce fire hazards. However, the same shrub removal may be detrimental to other types of wildlife. Changes in vegetation composition/ density/ age structure/ continuity across the landscape can affect evapo-transpiration losses and thereby influence antecedent soil moisture conditions, water yields & their timings, stream flow volumes & their peaks, at different parts of watersheds. Overgrazing -which results in excess trampling in a watershed and excessive soil 17 www.AgriMoon.Com Watershed Planning and Management compaction, reduces infiltration capacity and increases surface runoff. Roads and trails possibly increase soil erosion due to the exposure to erodible soil and subsoil during their construction. This reduces infiltration and concentrates overland flow from precipitation excess which erodes the increased gradients in the side slopes of cuts and fills. The increase in flooding due to the creation of finished impervious surfaces as well as due to the filling up of water bodies especially in the urbanized areas leading to a drastic reduction in infiltration or surface storage is very well known. On the other hand, forest and wild land watersheds are frequently affected by wild fires. This results in increased soil erosion due to the loss in the vegetation cover and also an increased surface runoff due to the formation of water repellent layers in the soil. These are some of the examples wherein a change in land use has impacted the watersheds and made them ecologically unsustainable. There are many other examples of land use changes which also disturb the watersheds in terms of water quality, geomorphic and hydrologic effects. To overcome these undesirable effects, an interdisciplinary approach involving hydrology, geomorphology and ecology into watershed management and land use planning is needed to understand and appreciate the impacts of cumulative watershed effects on water yield, other stream flow characteristics and water quality. The next section will deal with the planning the land use so as to ensure sustainability in watershed management. 4.2 Planning the Land Use There are conflicts over land use, many a times. The demands for arable land, grazing, forestry, wildlife, tourism and urban development are greater than the land resources available. In the developing countries, these demands become more acute every year. The population dependent on the land for food, fuel and employment is expected to double within the next 25 to 50 years. Even where land is still available in plenty, many people may have inadequate access to land or to the benefits from its use. In the face of scarcity, the degradation of farmland, forest or water resources are visible for all to see but individual land users lack the incentive or resources to stop it. Land-use planning is the systematic assessment of land and water potential, alternatives for land use and economic and social conditions in order to select and adopt the best land-use options. Its purpose is to select and put into practice those land uses that will best meet the needs of the people while safeguarding the resources for the future. The driving forces in land use planning are the needs for change, improved management or quite different patterns of land use dictated by the changing circumstances. All kinds of rural land use like agriculture, pastoral lands, forestry, wildlife conservation and tourism are involved in land use planning. It also provides guidance in cases of conflict between rural land use and urban or industrial expansion, by indicating which areas of land are most valuable under rural use. The following two conditions must be met if the land use planning is to be useful: 1. The need for changes in land use or the action to prevent some unwanted changes which must be accepted by the people involved; 18 www.AgriMoon.Com Watershed Planning and Management 2. There must be the political will and ability to put the plan into effect. Wherever these two conditions are not met and the problems are pressing, it may be appropriate to mount an awareness campaign or set up demonstration areas with the aim of creating the conditions necessary for effective planning. Our basic needs of air, water, food, clothing shelter and fuel must be met from the land which is in limited supply. As population and aspirations increase, the land becomes an increasingly scarce resource. Land must change to meet new demands which may bring new conflicts among the competing uses of the land and among the interests of individual land users and the common good. Land taken for towns and industry is no longer available for farming. Likewise, the development of new farm land may compete with forestry, water supplies and wildlife. Planning to make the best use of land is an established idea. Over the years, farmers have made plans season after season, deciding what to grow and where to grow it. Their decisions have been made according to their own needs, knowledge of the land & the technology, labour and capital available. As the size of the area, the number of people involved and the complexity of the problems increase, the need for information and rigorous methods of analysis and planning also increase. However, land-use planning is not just farm planning on a different scale. It has a further dimension, namely the interest of the whole community. Planning involves anticipation of the need for change as well as reactions to it. Its objectives are set by social or political requirements which take into account of the existing situation. In many places, the existing situation cannot continue because the land itself is being degraded. Examples of unwise land use include the following: (a) The clearance of forest on steep lands or on poor soils for which sustainable systems of farming have not been developed so far (b) Overgrazing of pastures (c) Industrial, agricultural and urban activities that produce pollution. Degradation of land resources may be attributed to human greed, ignorance, uncertainty or lack of an alternative but essentially, it is a consequence of using land today without investing in tomorrow. Land-use planning aims to make the best use of limited resources by the following actions: 1. Assess the present, future needs and systematically evaluating the land's ability to supply them; 2. Identify and resolve the conflicts among competing uses, the needs of individuals and those of the community, and among the needs of the present generation and those of future generations; 3. Seek sustainable options and choose those which fully meet identified needs; 4. Plan to bring about desired changes; and, 5. Learn from experience. 19 www.AgriMoon.Com Watershed Planning and Management There can‘t be a blueprint for change. The whole process of planning is iterative and continuous. At every stage, as better information is obtained, a plan may have to be changed to take account of it. i) Goals of Land Use Planning Goals of land use planning define what is meant by the "best" use of the land. They should be specified at the outset of a particular land use planning project. Goals may be grouped under the following three headings of efficiency, equity & acceptability and sustainability. Efficiency: Land use planned must be economically viable. Therefore, one goal of development planning is to make an efficient and productive use of the land. For any particular land use, certain areas are better suited than others. Efficiency is achieved by matching different land uses with the areas that will yield the greatest benefits at the least cost, i.e., maximum benefit cost ratio. Efficiency might mean different things to different people. To the individual land user, it means the greatest return on capital and labour invested or the greatest benefit from the land area available. Government objectives are more complex: they may include improving the foreign exchange situation by producing for export or for import substitution. Equity & Acceptability: Land use must be socially acceptable. It should ensure food security, employment and income security in rural areas. Land improvements and redistribution of land may be undertaken to reduce inequality or to attack absolute poverty. One way of doing this is to set a threshold standard of living to which the target groups should be raised. Living standards may include levels of income, nutrition, food security and housing. Planning to achieve these standards involves the allocation of land for specific uses as well as the allocation of financial and other resources. An example of acceptability is given here. Following the drought of 1973-74 and the subsequent famine, the Government of Ethiopia became more aware of the serious degradation of soil in the highlands. An ambitious soil conservation programme which concentrated on protecting steep slopes by bunding and afforestation was launched. This had made a substantial impact on soil erosion but has not contributed much to in increasing agricultural production. Large-scale afforestation was also unpopular with local people because it reduced the area available for livestock grazing while forest protection implied denying access to the public for fuel wood collection. A balance between the competing requirements of conservation and production was clearly needed if popular support for soil conservation work was to continue without inducements such as the Food-for-Work Programme. A land-use plan to conserve steeper slopes by restoring good vegetative cover through closure, followed by controlled grazing, was found to be more acceptable to the local people than large-scale afforestation applied in isolation. Sustainability: Sustainable land use is that which meets the needs of the present while simultaneously conserving resources for future generations. This requires a combination of production and conservation. The production of the goods required by the people now need to be 20 www.AgriMoon.Com Watershed Planning and Management combined with the conservation of natural resources on which that production depends so as to ensure a continued production in the future. A community that destroys its land will forfeit its future. Land use has to be planned for the community as a whole because the conservation of soil, water and other land resources is often beyond the means of individual land users. ii) Trade-offs among Conflicting Goals of Land Use Planning Clearly, there are conflicts between these various goals of land use planning. More equity may lead to less efficiency. In the short term, it may not be possible to meet the needs of the present without consuming resources such as burning oil or clearing areas of natural forest. Decision-makers need to consider the trade-offs between different goals. But if the system as a whole is to survive, the use of natural assets must be compensated by the development of human or physical assets of equal or greater worth. Good information such as information about the needs of the people, about land resources and about the economic, social and environmental consequences of alternative decisions is always essential. The job of the land use planner is to ensure that decisions are made on the basis of consensus or acceptable degree of disagreement. In many cases, planning the processes like introducing appropriate new technology can reduce the costs in trade-off. It can also help in resolving the conflict by involving the community in the planning process and by revealing the rationale and information on which decisions are based. iii) The Focus of Land Use Planning The following points constitute the focus of land use planning. Land Use Planning is for the People: People's needs are the driving forces in the land use planning process. Local farmers, other land users and the wider community who depend on land must accept the need for a change in land use, as they will have to live with its results. Land use planning must be positive and needs to be for the people‘s betterment. The planning team must find out about people's needs and also about the local knowledge, skills, labour and capital that they can contribute. It must study the problems of existing land use practices and seek alternatives while drawing the public attention to the hazards or inconveniences of continuing with the present practices and to the opportunities for change. Regulations to prevent people doing what they now do for pressing reasons are most likely to fail. Local acceptability is readily achieved by local participation in land use planning. The support of local leaders is essential. At the same time, the participation of agencies that have the resources to implement the plan is also important. Land is not the Same Everywhere: Land is the other focus of land-use planning. Capital, labour, management skills and technology can be moved to where they are needed. On the other hand, land cannot be moved, and different areas present different opportunities and different management 21 www.AgriMoon.Com Watershed Planning and Management problems. The land resources are generally changing as it is obvious in the case of climate and vegetation. But the examples such as the depletion of water resources or the loss of soil by erosion or salinity remind us that resources can be degraded, many a times irreversibly. Good information about land resources is thus essential to land use planning. Technology: A third element in land use planning is the knowledge of technologies like agronomy, silviculture, livestock husbandry and other means by which land is used. The technologies recommended must be appropriate technologies for which the users have the capital, skills and other necessary resources. New technologies may have social and environmental implications that should be addressed by the land use planner(s). Integration: A mistake in early attempts at land use planning was to focus too narrowly on land resources without enough thought given to their possible use. Good agricultural land is usually also suitable for other competing uses. Land use decisions are not made only on the basis of land suitability but also according to the demand for products and the extent to which the use of a particular area is critical for a particular purpose. Planning has to integrate information about the suitability of the land, the demands for alternative products or uses and also the opportunities for satisfying those demands on the available land, now as well as in the future. Hence, land use planning is not sectoral. Even where a particular plan is focused on one sector, e.g., small holder tea development or irrigation, an integrated approach has to be carried down starting from the strategic planning at the national level to the details of the individual projects and programs at district and local levels. iv) Land Use Planning at Different Levels Land use planning can be applied at three broad levels: national, district and local. These are not necessarily in that order. They correspond to the levels of government at which decisions about land use are taken. Different kinds of decisions are taken at each level, where the planning methods and plan types also differ. However at each level there is a need for a land use strategy, policies that indicate planning priorities, projects that tackle these priorities and operational planning to get the work done smoothly, swiftly and cost-effectively. The greater the interaction between the three levels of planning, the better for all. The flow of information should be in both directions. At each successive level of planning, the degree of details needed as well as the direct participation of the local people increase. National Level Land Use Planning: At the national level, land use planning is concerned with the national goals and the allocation of resources. In many cases, national land use planning may not involve the actual allocation of land for different uses. In place of them, it may establish the priorities for district level projects. A national land use plan may cover: 1. Land-Use Policy related to balancing the competing demands for land among different sectors of the economy such as food production, export crops, tourism, wildlife conservation, housing & public amenities, roads, industry; 22 www.AgriMoon.Com Watershed Planning and Management 2. National Development Plans and Budget consisting of project identification and the allocation of resources for development; 3. Coordination of sectoral agencies involved in land use; 4. Legislation on such subjects as land tenure, forest clearance and water rights. National goals are complex while policy decisions, legislation and fiscal measures affect a large population and wide areas. Decision makers can‘t possibly be specialists in all facets of land use. So the planners' responsibility is to present the relevant information so that the decision makers can both understand and act on it. District Level Land Use Planning: District level refers not necessarily to administrative districts but also to land areas that fall between national and local levels. Development projects are generally at this level, where planning first comes to the grips with the diversity of the land and its suitability to meet the project goals. When planning is initiated nationally, national priorities need to be translated into local plans. Conflicts between national and local interests should be resolved. The kinds of issues tackled at this stage include: 1) The siting of developments such as new settlements, forest plantations, irrigation schemes, etc.; 2) The need for improved infrastructure such as water supply, roads, marketing facilities, etc.; 3) The development of management guidelines for improved types of land use on each type of land. Local Level Land Use Planning: The local planning unit may be the village, a group of villages or a small watershed or a catchment. At this level, it is very easy to fit the plan to the people, making use of local people's knowledge and contributions. Wherever the planning is initiated at the district level, the programme of work to implement changes in land use or management has to be carried out locally. Alternatively, this may be the first level of planning, with its priorities drawn up by the local people. Local level planning is about getting things done on particular areas of land including what shall be done where and when, and who will be responsible. Some of the examples of local level land use planning are: 1) Layout of drainage, irrigation and soil conservation works; 2) Design of infrastructure - road alignment and the siting of crop marketing, fertilizer distribution, milk collection or veterinary facilities; 3) Siting of specific crops on suitable land. Requests at the local level, e.g., for suitable areas to introduce tobacco or coffee, must be met with firm recommendations. Planning at these different levels needs information at different scales and levels of generalization. Much of this information may be available in maps. The most suitable map scale for national level land use planning is one by which the whole country fits on to one map sheet, which may call for a scale ranging from 1:5 million to 1:1 million or larger. District level land use 23 www.AgriMoon.Com Watershed Planning and Management planning requires details to be mapped at about 1:50000, although some information may be summarized at smaller scales ranging to 1:250000. For local level land use planning, maps in the scales ranging between 1:20000 and 1:5000 are found to be the best. Reproductions of air photographs can be used as base maps at the local level land use planning, since field workers and experience can show that local people can recognize where they are on the photos. v) Land Use in Relation to Sectoral and Development Planning Land use planning is non-sectoral by definition but, unless a special planning authority is set up, a land use plan must be implemented by sectoral agencies - in agriculture, forestry, irrigation, etc. Implementation will call for help from the different extension services. There will be no clear boundary between land use planning and other aspects of rural development. For example, a desirable change in land use may be the introduction of a cash crop. Successful management may require the use of fertilizers. This cannot be done unless there are local centres for fertilizer distribution, effective advice on its use and a system of credit for its purchase. Local services will be of no use without an adequate national distribution system and the sufficient manufacture or allocation of foreign currency for imports. Building a fertilizer factory and organizing national distribution are definitely not part of land use planning but they may be essential for the success of planned land use. On the other hand, the siting of local distribution centres in relation to population and suitable land could well be part of the work of a land use planner. Hence, there is a spectrum of activities ranging from focus on the interpretation of the physical qualities of the land for which the land use planner will be largely responsible to activities that need a combined input with other technical specialists. Furthermore, where matters of national policy such as adequate prices for crops are prerequisites for successful land use, the job of the planner(s) is to mention it clearly. vi) People Involved in Land Use Planning Land use planning involves getting many different people to work together towards common goals. The following three groups of people are directly involved: Land Users: These are the people living in the planning area whose livelihood depends wholly or partly on the land. They include not only the farmers, herders, foresters and others who use the land directly but also those who depend on these people's products such as operators in crop or meat processing, sawmills and furniture factories. The involvement of all land users in planning is very essential. Ultimately, they have to put the plan into practice and must therefore believe in its potential benefits as well as in the fairness of the planning process. The experience and determination of local people in dealing with their environment are generally the most neglected in spite of being the most important resource. People will grasp development opportunities that they themselves have helped to plan more readily than any other schemes that are imposed on them. Without the support of local leaders, a plan is not likely to succeed. 24 www.AgriMoon.Com Watershed Planning and Management Achieving effective public participation in planning is a real challenge. Planners have to invest the time and resources needed to secure participation through local discussions, by broadcasting and newspaper articles, through technical workshops and extension services. Imagination, a sincere interest in people and the land as well as a willingness to experiment mark the more successful efforts by the land users. Decision Makers: Decision makers are those responsible for putting plans into effect. At the national and district levels, they will usually be government ministers. At the local level, they will be members of the local self-government or other authorities. Generally, the planning team provides information and expert advice. The decision makers guide the planning team on key issues and goals while also deciding whether to implement plans and if so, which of the options presented need to be chosen. Although the leader of the planning team is in charge of the day-to-day planning activities, the decision maker(s) should be involved at regular intervals. Decision makers also have a key role in encouraging public participation through their willingness to expose their decisions and the way they are reached to public scrutiny. Land Use Planning Team: An essential feature of land use planning is the treatment of land and land use as a whole. This involves crossing boundaries between disciplines like natural resources, engineering, agriculture and social sciences. Therefore teamwork is essential. Ideally a team needs a wide range of special expertise such as a soil surveyor, a land evaluation specialist, an agronomist, a forester, a range and livestock specialist, an engineer, an economist and a sociologist. Such a range may be available only at the national level. At the local level, a more typical planning team may consist of a land use planner and one or two assistants. Each member must tackle a wide range of jobs and will subsequently need specialist advice. Government agency staff and universities may be useful sources of such advice or assistance. Applications of Remote Sensing and Geographical Information System (GIS) in Watershed Planning Remote sensing and GIS two of the important modern tools which have many applications in watershed planning. In this section, the remote sensing applications in watershed planning are discussed followed by the GIS applications. Doppler RADAR (i.e., Radio Amplification Detection and Ranging) is used in the enhanced meteorological collection of data such as wind speed and direction within weather systems. By measuring the bulges of water caused by gravity, features on the seafloor to a resolution of about a mile are mapped. By measuring the height and wavelength of ocean waves, the altimeters measure wind speeds and direction and surface ocean currents and directions. Light detection and ranging (LIDAR) is used to detect and measure the concentration of various chemicals in the atmosphere, while airborne Heights of objects and features on the ground can be measured more accurately by LIDAR than radar technology. Remote sensing of vegetation cover is a principal application of LIDAR. Simultaneous multispectral platforms such as the images from the Landsat remote sensing satellite have been in use since the 1970s. Maps of land cover and land use from thematic mapping can be used to find 25 www.AgriMoon.Com Watershed Planning and Management minerals, detect or monitor land usage and deforestation and examine the health of indigenous plants and crops, including entire farming regions or forests. Within the scope of the combat against desertification, remote sensing allows to follow up and monitor risk areas in the long term, to determine desertification factors, to support decision-makers in defining the relevant measures of environmental management and to assess their impact on watershed planning. After the successful launching of India‘s remote sensing satellites viz., Bhaskara 1 and Bhaskara 2 in 1979 and 1981, respectively, India began developing an indigenous Indian Remote Sensing (IRS) satellite program to support the national economy in the areas of agriculture, water resources, forestry and ecology, geology, watersheds, marine fisheries and coastal management. The Indian Remote Sensing satellites are the mainstay of National Natural Resources Management System (NNRMS) for which Government of India‘s (GoI) Department of Space (DOS) is the nodal agency, providing operational remote sensing data services. Data from the IRS satellites are received and disseminated. With the advent of high-resolution satellites, new applications in the areas of urban sprawl, infrastructure planning and other large-scale applications for mapping have been initiated. Remote sensing applications in the country, under the umbrella of NNRMS, now cover diverse fields within the domain of watershed planning and management such as pre-harvest crop area and production estimation of major crops, drought monitoring and assessment based on vegetation condition, flood risk zone mapping etc. GIS has been widely used in characterization and assessment studies which require a watershed- based approach. Basic physical characteristics of a watershed such as the drainage network and flow paths can be derived from readily available Digital Elevation Models (DEMs) and data such as the United States Geological Survey‘s (USGS) National Hydrography Dataset (NHD) Program. This, in conjunction with precipitation and other water quality monitoring data from sources such as the Environmental Protection Agency‘s (EPA) BASINS (i.e., Better Assessment Science Integrating Point & Non-point Sources) database and USGS, enhances development of a watershed action plan and identification of existing and potential pollution problems in the watershed. Data gathered from Global Positioning System (GPS) surveys and from environmental remote sensing systems can be fused within a GIS for a successful characterization and assessment of watershed functions and conditions. Management Planning When faced with challenges involving water quality and quantity due to natural as well as human- induced hazards (e.g., droughts, hazardous material spills, floods, and urbanization), planning becomes extremely important so as to mitigate their impacts and ensure optimal utilization of the available resources. Information obtained from characterization and assessment studies, primarily in the form of charts and maps, can be combined with other datasets to improve understanding of the complex relationships between natural and human systems as they relate to land and resource use within watersheds. GIS provides a common framework [i.e., spatial location] for watershed management data obtained from a variety of sources. Because watershed data and watershed 26 www.AgriMoon.Com Watershed Planning and Management biophysical processes have spatial dimensions, GIS can be a powerful tool for understanding these processes and for managing potential impacts of human activities. The modeling and visualization capabilities of modern GIS, coupled with the explosive growth of the Internet and the World Wide Web, offer fundamentally new tools to understand the processes and dynamics that shape the physical, biological and chemical environment of watersheds. The linkage between GIS, the Internet, and environmental databases is especially helpful in planning studies where information exchange and feedback on a timely basis is very crucial and more so when there are several different agencies and stakeholders involved. Watershed Restoration (Analysis of Alternative Management Strategies) Watershed restoration studies generally involve evaluation of various alternatives and GIS provides the perfect environment to accomplish that efficiently and accurately. GIS has been used for restoration studies ranging from relatively small rural watersheds to heavily urbanized landscapes. Coupled with hydrodynamic and spatially explicit hydrologic/water quality modeling, GIS can assist in unified source water assessment programs including the total maximum daily load (TMDL) program. As an example, alternatives for restoring a waterbody or a watershed can be studied by creating digital maps that show existing conditions and comparing them to maps that represent the alternative scenarios. GIS can also provide a platform for collaboration among researchers, watershed stakeholders, and policy makers, significantly improving consensus building and offering the opportunity for collaborative work on interdisciplinary environmental policy questions. The integrating capabilities of a GIS provide an interface to translate and emulate the complexities of a real world system within the confines of a digital world accurately and efficiently. Watershed Policy Analysis and Decision Support The field of watershed science, particularly watershed planning, is experiencing fundamental changes that are having profound impact on the use of computer-based simulation models in resource planning and management. On one hand, the dramatically increased availability of powerful, low-cost, and easy-to-use GIS software, and more extensive spatially referenced data, are making GIS an essential tool for watershed planning and management tasks. However, with this increased use has come an increased realization that GIS alone cannot serve all the needs of planning and managing watersheds. This realization has renewed resource planners‘ interest in development of decision support systems that combine GIS, spatial and non-spatial data, computer-based biophysical models, knowledge-based (i.e., expert) systems, and advanced visualization techniques into integrated systems to support planning and policy analysis functions. As a component of a spatial decision support system, GIS provides very powerful visualization facilities for display and manipulation, giving immediate intuitive evaluation capabilities to which a wide range of non- technical users and decision makers can relate to. GIS can assist the decision maker in dealing with complex management and planning problems within a watershed, providing geo-processing functions and flexible problem- solving environments to support the decision research process. 27 www.AgriMoon.Com Watershed Planning and Management A casual look at the environmental/ecological science literature reveals intense research activities in GIS-based watershed management and planning. The explosive growth in the use of GIS for the activities listed above is testimony to its rapid evolution into a complex array of applications and implementations. Keywords: Land use, impact on watershed, land use planning, land use goals, land use trade-offs. 28 www.AgriMoon.Com Watershed Planning and Management Module 3: Watershed Characteristics: Physical and Geomorphologic Factors affecting Watershed Management Lesson 5 Watershed Characteristics: Classification and Measurement 5.1 Characteristics of Watersheds A watershed is a basic unit of hydrological behavior. On the land surface, it is a geographical unit in which the hydrological cycle and its components can be analyzed. Usually a watershed is defined as the area that appears, on the basis of topography, to contribute all the water that passes through a given point of a stream. A watershed embraces all its natural and artificial (man-made) features, including its surface and subsurface features, climate and weather patterns, geologic and topographic settings, soils and vegetation characteristics, and land use (shown in figure 5.1). A watershed carries water ―shed‖ from the land after rain falls and snow melts. Drop by drop, water is channeled into soils, groundwater, creeks, and streams, making its way to larger rivers and eventually the sea. Fig. 5.1. A Watershed Illustration. (Source: Rees, 1986) 5.2 Classification of Watershed Watersheds can be classified using any measurable characteristics in the area like- size, shape, location, ground water exploitation, and land use. However, the main classification of watershed is discussed broadly on the basis of size and land use. Two watersheds of the same size may behave very differently if they do not have similar land and channel phases. The descriptions of different watershed classifications are as below. 29 www.AgriMoon.Com Watershed Planning and Management 5.2.1 Size – The main implication of watershed size appears in terms of spatial heterogeneity of hydrological processes. The spatial variability of watershed characteristics increases with size, therefore, large watersheds are most heterogeneous. As the watershed size increases, storage increases. Based on size, the watersheds are divided into three classes. 1. Small Watersheds < 250 km2 2. Medium Watersheds between 250 to 2500 km2 3. Large Watersheds > 2500 km2 5.2.1.1 Small Watersheds: Small watersheds are those, where the overland flow and land phase are dominant. Channel phase is relatively less conspicuous. The watershed is highly sensitive to high- intensity and short-duration rainfalls. 5.2.1.2 Medium Watersheds: Being medium in size, the workability in these watersheds are easy due to accessible approach. Rather than size, shape of the watershed plays a dominant role. Overland flow and land phase are prominent. 5.2.1.3 Large Watersheds: These watersheds are less sensitive to high-intensity-rainfalls of short duration. The channel networks and channel phase are well-developed, and, thus, channel storage is dominant. 5.2.2 Land Use – Land use defines the exploitation (natural and human interactions) characteristics of watersheds which affect the various hydrological processes within the watershed. The watershed classification based on the land use can be given as below. 1. Agricultural 2. Urban 3. Mountainous 4. Forest 5. Desert 6. Coastal or marsh, or 7. Mixed - a combination of two or more of the previous classifications 5.2.2.1 Agricultural Watershed: Agricultural watershed is the watershed in which agricultural activities (crop cultivation) is dominant. It experiences perhaps the most dynamically significant land-use change. This usually leads to increased infiltration, increased erosion, and/or decreased runoff. Depression storage is also increased by agricultural operations. When the fields are barren, falling raindrops tend to compact the soil and infiltration is reduced. There is lesser development of streams in agricultural watersheds. The small channels formed by erosion and runoff in the area are 30 www.AgriMoon.Com Watershed Planning and Management obliterated by tillage operations. The soil structure is altered by regular application of organic and/or inorganic manure. This, in turn, leads to changed infiltration characteristics. 5.2.2.2 Urban Watershed: These are the watershed areas having maximum manipulation for the convenience of human being. These are dominated by buildings, roads, streets, pavements, and parking lots. These features reduce the infiltrating land area and increase imperviousness. As drainage systems are artificially built, the natural pattern of water flow is substantially altered. For a given rainfall event, interception and depression storage can be significant but infiltration is considerably reduced. As a result, there is pronounced increase in runoff and pronounced decrease in soil erosion. Thus, an urban watershed is more vulnerable to flooding if the drainage system is inadequate. Once a watershed is urbanized, its land use is almost fixed and its hydrologic behavior changes due to changes in precipitation. 5.2.2.3 Mountainous Watershed: Because of higher altitudes, such watersheds receive considerable snowfall. Due to steep gradient and relatively less porous soil, infiltration is less and surface runoff is dominantly high for a given rainfall event. The areas downstream of the mountains are vulnerable to flooding. Due to snow melt, water yield is significant even during spring and summer. 5.2.2.4 Forest Watershed: These are the watersheds where natural forest cover dominates other land uses. In these watersheds, interception is significant, and evapotranspiration is a dominant component of the hydrologic cycle. The ground is usually littered with leaves, stems, branches, wood, etc. Consequently, when it rains, the water is held by the trees and the ground cover provided greater opportunity to infiltrate. The subsurface flow becomes dominant and there are times when there is little to no surface runoff. Because forests resist flow of overland water, the peak discharge is reduced. Complete deforestation could increase annual water yield by 20 to 40 %. 5.2.2.5 Desert Watershed: There is little to virtually no vegetation in desert watersheds. The soil is mostly sandy and little annual rainfall occurs. Stream development is minimal. Whenever there is rainfall, most of it is absorbed by the porous soil, some of it evaporates, and the remaining runs off only to be soaked in during its journey. There is limited groundwater recharge due to occurrence of less rainfall in these watersheds. 5.2.2.6 Coastal Watershed: The watersheds in coastal areas may partly be urban and are in dynamic contact with the sea. Their hydrology is considerably influenced by backwater from wave and tidal action of the sea. Usually, these watersheds receive high rainfall, mostly of cyclonic type, do not have channel control in flow, and are vulnerable to severe local flooding. In these watersheds, the water table is high, and saltwater intrusion threatens the health of coastal aquifers, which usually are a source of the fresh water supply. 5.2.2.7 Marsh or Wetland Watershed: Such lands are almost flat and are comprised of swamps, marshes, water courses, etc. They have rich wildlife and plenty of vegetation. As water is no limiting factor to satisfy evaporative demand, evaporation is dominant. Rainfall is normally high and infiltration is minimal. Most of the rainfall becomes runoff. The flood hydrograph peaks gradually and lasts for a long time. 31 www.AgriMoon.Com Watershed Planning and Management 5.2.2.8 Mixed Watershed: These are the watersheds, where multiple land use/land cover exists either because of natural settings or due to a combination of natural and human interaction activities. In these watersheds, a combination of two or more of the previous classifications occurs and none of the single characteristics dominate the area. In India, most of the watersheds are of mixed nature of characteristics, where agriculture, forest, settlements (urban and rural) etc. land use occurs. 5.3 Watershed Characteristics: Physical and Geomorphologic Characteristics associated with Watersheds Watershed geomorphology refers to the study of the characteristics, configuration and evolution of land forms and properties; developing physical characteristics of the watershed. It comprises of the characteristics of land surface as well as the characteristics of the channels within the watershed/basin boundary. These properties of watersheds significantly affect the characteristics of runoff and other hydrological processes. The principal watershed characteristics are: 1. Basin Area 2. Basin Slope 3. Basin Shape 4. Basin Length Basin shape is reflected by a number of watershed parameters as are given below. 1. Form Factor 2. Shape Factor 3. Circularity Ratio 4. Elongation Ratio 5. Compactness Coefficient Along with the surface characteristics of a watershed, the channel characteristics are important in transiting the runoff water from the overland region to channels (streams) and also from the channel of one order (primary) to the other higher order (e.g. river stream). The most common and important channel characteristics of the watersheds are: 1. Channel Order 2. Channel Length 3. Channel Slope 4. Channel Profile 5. Drainage Density 32 www.AgriMoon.Com Watershed Planning and Management The quantification of these physical and geomorphologic properties of watershed/basin are important for estimating the watershed hydrologic processes. 5.4 Quantitative Characteristics of Watersheds 5.4.1 Physical Characteristics Watershed geomorphology refers to the physical characteristics of the watershed. Basin area, basin length, basin slope, and basin shape are the physical characteristics of watersheds, significantly affecting the characteristics of runoff and other hydrologic processes. The quantification of these watershed/basin characteristics can be done as discussed below. 5.4.1.1 Basin Area: The area of watershed is also known as the drainage area and it is the most important watershed characteristic for hydrologic analysis. It reflects the volume of water that can be generated from a rainfall. Once the watershed has been delineated, its area can be determined by approximate map methods, planimeter or GIS. Basin area is defined as the area contained within the vertical projection of the drainage divide on a horizontal plane. Watershed area is comprised of two sub-components; Stream areas and Inter-basin areas. The inter-basin areas are the surface elements contributing flow directly to streams of order higher than 1. Stream areas are those areas that would constitute the area draining to a predetermined point in the stream or outlet. For example, the stream area for first-order streams would be delineated by measuring the drainage area for each first-order channel. Horton (1945) inferred that mean drainage areas of progressively higher orders might form a geometric sequence. This characteristic was formulated as a law of drainage areas. where Aw = mean area of basins of order w, A1 = mean area of first-order basins, Ra = Stream Area Ratio and normally varies from 3 to 6 Ra = Aw/Aw-1 5.4.1.2 Basin Length: Length can be defined in more than one way (Fig. 5.2) - 1. The greatest straight-line distance between any two points on the perimeter 2. The greatest distance between the outlet and any point on the perimeter 3. The length of the main stream from its source (projected to the perimeter) to the outlet 33 www.AgriMoon.Com Watershed Planning and Management Fig. 5.2. Diagram Defining Basin Length. (Source: Zavoianu, 2011) Conceptually the basin length is the distance traveled by the surface drainage and sometimes more appropriately labeled as hydrologic length. This length is generally used in computing a time parameter, which is a measure of the travel time of water through a watershed. The watershed length is therefore measured along the principal flow path from the watershed outlet to the basin boundary. Since the channel does not extend up to the basin boundary, it is necessary to extend a line from the end of the channel to the basin boundary. The measurement follows a path where the greatest volume of water would generally travel. Basin length, Lb, is the longest dimension of a basin parallel to its principal drainage channel and Basin width can be measured in a direction approximately perpendicular to the length measurement. The relation between mainstream length and drainage-basin area for small watershed is given below; where Lb is in km and A in km2. Lb = 1.312 A0.568 5.4.1.3 Basin Slope: Watershed/basin slope affects the momentum of runoff. It reflects the rate of change of elevation with respect to distance along the principal flow path. It is usually calculated as the elevation difference between the endpoints of the main flow path divided by the length. The elevation difference may not necessarily be the maximum elevation difference within the watershed since the point of highest elevation may occur along a side boundary of the watershed rather than at the end of the principal flow path. If there is significant variation in the slope along the main flow path, it may be preferable to consider several sub-watersheds and estimate the slope of each. Basin slope has a profound effect on the velocity of overland flow, watershed erosion potential, and local wind systems. Basin slope S is defined as S = h/L where h = fall in meters, and L = horizontal distance (length) over which the fall occurs. 5.4.1.4 Basin Shape: Basin shape is not usually used directly in hydrologic design methods; however, parameters that reflect basin shape are used occasionally and have a conceptual basis. Watersheds have an infinite variety of shapes, and the shape supposedly reflects the way that runoff will ―bunch up‖ at the outlet. A circular watershed would result in runoff from various parts of the watershed reaching the outlet at the same time. An elliptical watershed having the outlet at one end of the major axis and having the same area as the circular watershed would cause the runoff to be spread out over 34 www.AgriMoon.Com Watershed Planning and Management time, thus producing a smaller flood peak than that of the circular watershed. A number of watershed parameters have been developed to reflect basin shape. Form factor, shape factor, circularity ratio, elongation ratio, and compactness coefficient are the typical parameters; important in defining the shape of a watershed/basin; and are discussed as below. 5.4.1.5 Form Factor: The area of the basin divided by the square of axial length of the basin; where value < 1 A/L2 5.4.1.6 Shape Factor: The drainage area divided by the square of the main channel length; where value > 1 L2/A 5.4.1.7 Circularity Ratio: The ratio of basin area to the area of a circle having the same perimeter as the basin; where value £ 1 12.57 A/Pr2 5.4.1.8 Elongation Ratio: The ratio of the diameter of a circle of the same area as the basin to maximum basin length; where value £ 1 1.128A0.5/L Compaction Coefficient: The perimeter of the basin divided by circumference of equivalent circular area; where value ³ 1 0.2821Pr/A0.5 5.4.2 Channel Characteristics The basin geomorphology plays an important role in the transition of water from the overland region to channels (streams) and also from the channel of one order to the other. It is easily determined by contour map and drainage map of the basin. Channel order, channel length, channel slope, channel profile, and drainage density are the most common channel characteristics, important in estimating the watershed hydrological processes and are discussed as below. 5.4.2.1 Channel Order: The first-order streams are defined as those channels that have no tributaries. The junction of two first-order channels form a second-order channel. A third-order channel is formed by the junction of two second-order channels. Thus, a stream of any order has two or more tributaries of the previous lower order. This scheme of stream ordering is referred to as the Horton- Strahler ordering scheme (Fig.5.3) 35 www.AgriMoon.Com Watershed Planning and Management Fig. 5.3. The Horton-Strahler ordering scheme. (Source: http://www.fgmorph.com/fg_4_8.php) Nw = RbW-w Or log Nw = W log Rb - w log Rb = a – b (a= W log Rb, b=w log Rb) where Nw = number of streams of order w; W = order of the watershed; and R b = Bifurcation Ratio varies between 3 and 5. This law is an expression of topological phenomenon, and is a measure of drainage efficiency. Bifurcation ratio is defined as the ratio between the number of streams of a particular order to the number of streams of one higher order. Rb = Nw/Nw+1 5.4.2.2 Channel Length: This refers to the length of channels of each order. The average length of channels of each higher order increases as a geometric sequence. Thus, the first-order channels are the shortest of all the channels and the length increases geometrically as the order increases. This relation is called Horton's law of channel lengths and can be formulated as: where Lw = total length of all channels of order w; Nw = number of channels of order w; Lw = mean channel length of order w; L1 = mean length of the first-order streams; RL = Stream-Length Ratio generally varies between 1.5 and 3.5 RL = Lw/Lw-1 36 www.AgriMoon.Com Watershed Planning and Management 5.4.2.3 Channel Slope: The channel slope is determined as the elevation difference between the endpoints of the main channel divided by the channel length. 5.4.2.4 Channel Profile: It includes the point of origin of the stream called the head, the point of termination called the mouth, and a decreasing gradient of the stream channel towards the mouth. 5.4.2.5 Drainage Density: Drainage density (Dd) is the measure of closeness of drainage spacing. It is the indication of drainage efficiency of overland flow and the length of overland flow as well as the index of relative proportions. It is defined as the length of drainage per unit area. This term was first introduced by Horton (1932) and is expressed as Dd = L/A or where L = Total length of all channels of all orders, A = Area; W = Basin order; N w = No. of basin of different order. Horton (1945) recommended using one-half the reciprocal of the drainage density to determine the average length of overland flow (L0) for the entire drainage basin L0 = 1/(2 Dd) Where Dd basically describes the average distance between streams and L0 approximates the average length of overland flow from the divides of the stream channels. Keywords: Watershed Characteristics, Channel Characteristics, Watershed Classification, Morphometric Characteristics 37 www.AgriMoon.Com Watershed Planning and Management Lesson 6 Importance of Watershed Properties for Watershed Management 6.1 Watershed Management Watershed management is the study of the relevant characteristics of a watershed aimed at the sustainable distribution of its resources. Watershed management is an important aspect of creating and implementing plans, programs, and projects to sustain and enhance watershed functions that affect the plant, animal, and human communities within a watershed boundary. 6.1.1 Objectives of Watershed Management The different objectives of watershed management programs are: 1. To control damaging runoff and degradation and thereby conservation of soil and water. 2. To manage and utilize the runoff water for useful purpose. 3. To protect, conserve and improve the land of watershed for more efficient and sustained production. 4. To protect and enhance the water resource originating in the watershed. 5. To check soil erosion and to reduce the effect of sediment yield in the watershed. 6. To rehabilitate the deteriorating lands. 7. To moderate the floods peaks at downstream areas. 8. To increase infiltration of rainwater. 9. To improve and increase the production of timbers, fodder and livestock resources. 10. To enhance the ground water recharge, wherever applicable. 6.2 Effect of Physical Properties on Watershed Management Certain physical properties of watersheds significantly affect the characteristics of runoff and as such are of great interest in hydrologic analyses. The effects of each physical property on watershed management are described under the following contents. 6.2.1 Size The size of the watershed has significant effect on its function. Size of watershed determines the quantity of rainfall received retained and disposed off (runoff). A small watershed is pronounced by overland flow which is main contributor to result a peak flow. While a large watershed has no overland flow significantly, but channel flow is the main characteristic. Large watersheds are also affected by basin storage. Watershed size plays a role here, as it interacts with the extent of land use 38 www.AgriMoon.Com Watershed Planning and Management changes, as well as factors that affect weather and climate. In smaller watersheds, the predominant interaction is between weather scale runoff-causing events and the storm hydrograph; whereas, in larger watersheds, the predominant interaction is between climate-scale runoff-causing events and the annual hydrograph. While large-scale events or land use changes may impact small watersheds and even the storm hydrograph in large watersheds, smaller, localized runoff-causing events tend to produce more intensive precipitation over restricted areas, thus having a greater impact on the storm hydrograph in small watersheds or on small tributaries to larger watersheds. 6.2.2 Shape The common watershed may be of square, rectangular, oval, fern leaf shaped, polygon-shaped, circular or triangular type and long or narrow. Larger the watershed, higher is the time of concentration and more water will infiltrate, evaporate or get utilized by the vegetation. Reverse is the situation when watershed is shorter in length as compared to width. The shape of the land, determined by geology and weather, greatly influences drainage patterns. The density of streams and the shape of a watershed, in turn, affect the rate of overland runoff relative to infiltration. A circular watershed would result in runoff from various parts of the watershed reaching the outlet at the same time. An elliptical watershed having the outlet at one end of the major axis and having the same area as the circular watershed would cause the runoff to be spread out over time, thus producing a smaller flood peak than that of the circular watershed. 6.2.3 Topography Topographic configuration such as slope, length, degree and uniformity of slope affect both disposal of water and soil loss. Time of concentration and infiltration of water are thus a function of degree and length of slope of the watershed. 6.2.4 Drainage Topography regulates drainage. Drainage density (length of drainage channels per unit area), length, width, depth of main and subsidiary channel, main outlet and its size depend on topography. Drainage pattern affect the time of concentration. A watershed with a high drainage density is characterized by quick response. Further, drainage cross section information is needed to determine the extent of flooding during high flows. 6.2.5 Area of the Watershed The area of watershed is also known as the drainage area and it is the most important watershed characteristic for hydrologic analysis. It reflects the volume of water that can be generated from a rainfall. Determination of a workable size of watershed area is important for a successful watershed management programme. 6.2.6 Length of Watershed Conceptually this is the distance traveled by the surface drainage and sometimes more appropriately labeled as hydrologic length. This length is usually referred for computing a time parameter, which is a measure of the travel time of water through a watershed (time of concentration). The watershed 39 www.AgriMoon.Com Watershed Planning and Management length is therefore measured along the principal flow path from the watershed outlet to the basin boundary. Since the channel does not extend up to the basin boundary, it is necessary to extend a line from the end of the channel to the basin boundary. 6.2.7 Slope of Watershed Watershed slope affects the momentum of runoff. Both watershed and channel slope may be of interest. Watershed slope reflects the rate of change of elevation with respect to distance along the principal flow path. It is usually calculated as the elevation difference between the endpoints of the main flow path divided by the length. The elevation difference may not necessarily be the maximum elevation difference within the watershed since the point of highest elevation may occur along a side boundary of the watershed rather than at the end of the principal flow path. If there is significant variation in the slope along the main flow path, it may be preferable to consider several sub- watersheds and estimate the slope of each sub-watershed. 6.3 Effect of Geomorphologic Factors and Associated Processes on Watershed Management 6.3.1 Geological Rocks and Soil: Geological formation and rock types affect extent of water erosion, erodability of channels and hill faces, and finally sediment production. Rocks like shale‘s, phyllites erode easily whereas igneous rocks do not erode. Physical and chemical properties of soil, specially texture, and structure and soil depth influence disposition of water by way of infiltration, storage and runoff. Soil types influence the rate of water movement (lateral and vertical) in the soil. For example, finely grained soils, such as clays, have very small spaces between soil particles, inhibiting infiltration and thus promoting greater surface runoff. Conversely, coarse soils, such as sands, have larger pore spaces allowing for greater rates of infiltration and reduced runoff. Surface roughness, soil characteristics such as texture, soil structure, soil moisture and hydrologic soil groups also affect the runoff in various ways. For example; Soil properties affect the infiltration capacity. Soil particles are usually classified as clay (d < 0.002 mm), silt (0.002 < d < 0.02), or sand (d > 0.02 mm). A particular soil is a combination of clay, silt, and sand particles. Generally, soils with a significant portion of small particles have low infiltration capacity, whereas sandy soils have high infiltration capacity. Fig. 6.1. Watershed Processes. 40 www.AgriMoon.Com Watershed Planning and Management 6.3.2 Climate: Climate parameters affect watershed functioning and its manipulation in two ways. Rain provides incoming precipitation temporally and spatially along with its various characteristic like intensity and frequency. The amount of rainfall and these parameters along with temperature, humidity, wind velocity, etc. regulates factors like soil and vegetation. Soil properties reflect the climate of the region. In the same way, the vegetation type of a region depends totally on the climate type. 6.3.3 Land Cover/ Vegetation: Depending upon the type of vegetation and its extent, this factor regulates the functioning of watershed; for eg. Infiltration, water retention, runoff production, erosion, sedimentation etc. Vegetation plays vital roles in the water cycle. It intercepts rainfall, impedes overland flow and promotes infiltration. Vegetation also uses water for growth. All of these factors reduce the quantity of runoff to streams. Vegetation binds and stabilizes soil, thereby reducing the potential for erosion. Vegetation also stabilizes stream banks and provides habitat for aquatic and terrestrial fauna. Vegetation functions to slow runoff and reduce soil compact