Hydrology Introduction PDF

HYDROLOGY Dr. Litan Kumar Ray  HYDROLOGY Sum of two terms: Hydro + Logus Hydro Water Hydrology Logus Study In a broad sense, HYDROLOGY can be defined as the STUDY OF WAT...

HYDROLOGY Dr. Litan Kumar Ray  HYDROLOGY Sum of two terms: Hydro + Logus Hydro Water Hydrology Logus Study In a broad sense, HYDROLOGY can be defined as the STUDY OF WATER  HYDROLOGY Science that attempts to answer the question Hydrology “What happens to the RAIN?” (Penman, 1961) Sounds like simple enough question but quantitative descriptions of the various processes involved are very complicated  NATIONAL WATER RESOURCES AT A GLANCE National Water Resources SL. Items Quantity No. (Cu.Km) 1. Annual Precipitation Volume (Including snowfall) 4000 2. Average Annual Potential flow in Rivers 1869 3. Per Capita Water Availability (1997) 1967 4. Estimated Utilizable Water Resources 1122 (i) Surface Water Resources 690 Cu.Km. (ii) Ground Water Resources 432 Cu.Km.  MAJOR RIVER BASINS National Water Resources 321289 sq km 12 Major River Basins 48 Medium River Basins 861452 sq km 141589 312812 258948  POPULATION GROWTH AND Water Management Issues WATER SUPPLIES Data: OWID based on UN world Urbanization prospects 2018 Urban and rural population projected to 2050 More than half of the population will live in urban area by 2050  POPULATION GROWTH AND WATER SUPPLIES Water Management Issues Projected Global Water Scarcity in 2025  POPULATION GROWTH AND Water Management Issues WATER SUPPLIES Already plenty of water and sanitation problems  Population, millions Water Management Issues 0 5 10 15 20 25 30 Migration of people from rural areas to cities Tokyo Megacities with more Bombay than 20 million people Lagos Shanghai mega water needs mega sewage flows Jakarta Sao Paulo Karachi Beijing Dhaka MexicoCity Top 10 Largest Cities by 2015  POPULATION GROWTH AND Water Management Issues WATER SUPPLIES For adequate living standards Western and Industrialised countries 2000 m3 per person per year Global renewal water supply 7000 m3 per person per year Enough water for at least three times the present population  POPULATION GROWTH AND Water Management Issues WATER SUPPLIES Projections or Estimates highlight the mismanagement  POPULATION GROWTH AND WATER SUPPLIES Water Management Issues Domestic: 8% Industry: 22% Major challenge will be in Inter-Sector Redistribution  WATER STORAGES Via Dams Water Management Issues Traditionally dams or surface reservoirs Good dam sites are getting scarce Disadvantages adverse environmental effects displacement of people increased waterborne diseases evaporation losses No sustainability lose capacity due to sedimentation  WATER STORAGES Via Artificial Recharge Water Management Issues Achieved by putting water on the land surface where it infiltrates into the soil and moves downwards to underlying groundwater In-channel T or L-shaped levees to spread water Off-channel specially constructed shallow ponds or basins Infiltration trenches Injection wells  CONJUNCTIVE USE Water Management Issues Often surface and groundwater are used conjunctively Tendency to pump more groundwater Aquifer depletion Salt water intrusion Higher pumping costs  RISE IN GROUNDWATER USE Water Management Issues  GROUNDWATER USE - INDIA Water Management Issues  Water Table Water Management Issues Decline >400 ft  WATER POLLUTION Water Management Issues Point Source Sewage and Industrial Waste Relatively simple to prevent and control Nonpoint Source Pollution of groundwater Agriculture Fertilizers, Pesticides, Salt containing irrigation water Intensification of agriculture to meet food demand Excess irrigation to leach the salts Salt tolerant plants Desalination of water Water Management Issues Aug 2006: Kerala, India ban on Coke and PepsiCo products after Centre for Science and Environment said they contained unsafe levels of pesticides. Six other states in India prohibited sales at or near schools, colleges and hospitals. Sep 2006: Kerala ban lifted by an Indian court due to inconsistencies in the group's analysis. ‘Coca-Cola India has always been completely confident of the safety of its soft drinks in India because they are produced to the same level of purity, regarding pesticides, as the EU criteria for bottled water (globally accepted as one of the most stringent in the world).’ Sep 29 2006 The Coca-Cola Company statement, www.coca-cola.com  CLIMATE CHANGE Water Management Issues Estimates are uncertain Globally average precipitation and its variability will increase Monsoon Rainfall over the north and central plains of India will decline Globally average evaporation will increase (Kimball 2002; Albritton 2001)  CLIMATE CHANGE Water Management Issues Soil Moisture will reduce Soil Characteristics may change due to water logging or cracking Soil moisture storage properties may consequently change (IPCC 1996) Total Runoff will increase unevenly worldwide (UKMO 1997) Catchment responses may change (Arnell 1996) Reduced water flow in Indian Rivers (Naithani 1998)  CLIMATE CHANGE Water Management Issues Crop ET will increase by 2-6% Seasonal crop water use will increase by 2-6% Cropping seasons may be altered Effect on irrigation requirement is uncertain due to uncertainties in projected precipitation patterns and soil moisture regimes (Kimball 2002)  HYDROLOGY Science that deals with Space-time characteristics of the Hydrology quantity and quality of the waters of the earth, encompassing their occurrence, movement, distribution, circulation, storage, exploration, development and management (Not a unique definition but indicative of its scope)  HYDROLOGY In a more strict sense it is the Hydrology Study of Hydrological Cycle (endless circulation of water between the earth and its atmosphere)  HYDROLOGICAL CYCLE Hydrology Hydrology HYDROLOGICAL CYCLE  HYDROLOGY CLASSIFICATION Hydrology Classification Customarily, Hydrology is partitioned into Surface-Water Hydrology – Relation between water and the surface of the earth Groundwater Hydrology – Relation between water and lithosphere (subsurface portion of the earth)  HYDROLOGY CLASSIFICATION Hydrology Classification Since water is closely associated with the atmosphere and the earth, hydrology is involved with several disciplines (interdisciplinary science) Therefore, many branches of hydrology have been distinguished  HYDROLOGY CLASSIFICATION Hydrology Classification Branch of Science Classification of Hydrology Agriculture Agrohydrology Meteorology Hydrometeorology Geology Hydrogeology Physics Physical Hydrology Forestry Forest Hydrology Oceanography Coastal Hydrology Glaciology Snow and Ice Hydrology Urban Resources Urban Hydrology  HYDROLOGICAL CYCLE Central focus of Hydrology Hydrological Cycle Water on the earth exits in Hydrosphere (extends about 15-km up into the atmosphere and about 1-km down into lithosphere) Hydrological cycle is constituted by the maze of paths through which water circulates in the hydrosphere A natural machine, constantly running distillation and pumping system  HYDROLOGICAL CYCLE From a global perspective, Hydrological Cycle Hydrological cycle may be considered to be comprised of three major systems: The Oceans – as the major source of The water Atmosphere – as the deliverer of The Land water – as the user of water Principal process that transmit water from one system to other Precipitation, Runoff, Evaporation  HYDROLOGICAL CYCLE Hydrological Cycle Precipitation Precipitation Stream Flow Atmospheric Earth Ocean System ET System Tidal Flow System Sea Rise GW intrusion Evaporation GLOBAL SCHEMATIC OF HYDROLOGICAL CYCLE  Precipitation Evapotranspiration Surface Runoff Land Hydrological Cycle System Exfiltration Infiltration Subsurface Stream Flow System Upward Percolation movement of moisture Aquifer System Groundwater Runoff SCHEMATIC OF THE HYDROLOGICAL CYCLE IN THE EARTH SYSTEM  Precipitation Hydrological Cycle Evapo-transpiration Evaporation Vegetation Structural Soil System System System Depression Interception Storage Throughflow Moisture Supply SCHEMATIC OF HYDROLOGICAL CYCLE IN THE LAND SYSTEM  HYDROLOGICAL STUDY APPROACH Hydrological Study Approaches Broadly two groups: PHYSICAL SCIENCE APPROACH – also referred to as Basic, Pure, Causal, dynamic or theoretical (BASIC RESEARCH) SYSTEMS APPROACH – also referred to as Operational, Applied, Empirical, Black- Box or Parametric (APPLIED RESEARCH)  HYDROLOGICAL STUDY APPROACH Hydrological Study Approaches The first group espouses the pursuit of scientific research into basic operation of each component of the hydrological cycle to gain a full understanding of their mechanism and interactions Ultimate aim is the full synthesis of the hydrological cycle (Only rational approach to hydrology)  HYDROLOGICAL STUDY APPROACH Hydrological Study Approaches The second group is motivated by the need to establish workable relationships between measured parameters in the hydrological cycle to be used in solving practical technological problems  HYDROLOGICAL BUDGET Hydrological Study Approaches Mathematical statement of hydrological cycle Inflow System Outflow Avg. outflow over t S Change in  I O storage over t t Avg. inflow over t If I and O vary continuously with time ds t   I t   O t  dt Spatially lumped continuity Eq. Any hydrological analyses must satisfy this Eq.  In volumetric terms, it can be expressed as S T  S 0  VI T VO T  Hydrological Study Approaches INCLUDING VARIOUS COMPONENTS OF HYDROLOGICAL CYCLE SS T  SS 0  SM T  SM 0  SG T  SG 0  SI T  SI 0  P VQ  E  T  F SURFACE SOIL MOISTURE GROUND WATER INTERCEPTION E, T, F, SI = HYDROLOGICAL ABSTRACTION VQ = BASIN YIELD Hydrological Study Approaches IN THIS APPROACH, We are not interested in the knowledge of runoff hydrograph at every point in the watershed We are not concerned with the geometry and topographic details We do not consider friction factor and its variability We do not worry about hydraulics of direct runoff and its space-time variability THUS, OUR EMPHASIS IS MORE ON THE SOLUTION OF THE PROBLEM AND LESS ON THE METHOD OF ARRIVING AT IT  CHOOSING BETWEEN APPROACHES Hydrological Study Approaches Choice depends on the requirement of 1. The User (accuracy, simplicity, amount of desired information) 2. The Problem 3. Approach (data availability, computational facility) 4. Economics Hydrological Study Approaches A choice among approaches depends on their system evaluations, which entails 1. Construction of an objective function 2. Use of goodness-of-fit criterion 3. Sensitivity analysis 4. Error analysis How a model (Physical or System) performs during validation?  SPACE-TIME SCALE IN HYDROLOGY Space-Time Scale in Hydrology Depending on the hydrological problem, under construction Hydrological cycle or its componets can be treated at different scales of TIME & SPACE SPACE Scale Largest -Global scale Small -Watershed scale Other -Continental, regional Space-Time Scale in Hydrology TIME Scale Highly dependent on the purpose of study and the problem involved Range:- Fraction of an hour to a year(s) Commonly used:- Hourly, daily, weekly, monthly or seasonal At times, time interval for collection of data determines the TIME Scale  PRECIPITATION CLASSIFICATION Precipitation Classification  PRECIPITATION CLASSIFICATION Precipitation Classification FORMS OF PRECIPITATION:  RAIN: Size of water droplet >0.5 mm and < 6 mm with intensity of rainfall > 1 mm/hr  DRIZZLE: Sprinkle of numerous water droplets of Size of water particle < 0.5 mm with intensity < 1 mm/hr  GLAZE: Ice coating formed when rain or drizzle comes in contact with cold ground at around 0̊ C  SLEET: Precipitation of snow and rain simultaneously  SNOW: Small ice crystals combine to form flakes  HAIL: Lumps of ice more than 8 mm in size  PRECIPITATION CLASSIFICATION Precipitation Classification Types of precipitation: 1. Orthographic Precipitation:  Presence of mountain barrier Wind ward side – Heavy rain fall Lee ward side – Less or scanty rain fall Ex: Western ghats, Himalayas  PRECIPITATION CLASSIFICATION 2. Convective Precipitation Classification Precipitation:  Heating up off Ground surface  Occurs when warm, moist air rises in the atmosphere  PRECIPITATION CLASSIFICATION 3. CYCLONE Precipitation Classification  Large low pressure region with circular wind motion  Two types: Tropical cyclone Extra tropical cyclone  Wind blow in anti clock wise direction in Northern hemisphere and clock wise in southern hemisphere  PRECIPITATION CLASSIFICATION 3. ANTI CYCLONE Precipitation Classification  High pressure region usually of large areal extent  Wind blow in clock wise direction in Northern hemisphere and anti clock wise in southern hemisphere Precipitation Classification PRECIPITATION CLASSIFICATION Characteristics of Classification CHARACTERISTICS OF PRECIPITATION IN INDIA  South-west monsoon (June- September) 75% of the annual rainfall is received  Transition-I, post-monsoon (October-November) Due to cause of severe tropical cyclones form in the Bay of Bengal and Arabian sea Occurs in Tamilnadu and coastal areas  Winter season (December-February) Moderate to heavy rain and snowfall due to cause of western disturbances Occurs in Himalayas and Jammu and Kashmir  Transition-II, Summer (March-May) Very little rainfall in India Mainly occurs in Kerala, West Bengal and Assam Characteristics of Classification CHARACTERISTICS OF PRECIPITATION IN INDIA Normal dates of Onset of Monsoon Characteristics of Classification CHARACTERISTICS OF PRECIPITATION IN INDIA Normal dates of with-drawal of monsoon Characteristics of Classification CHARACTERISTICS OF PRECIPITATION IN INDIA Southwest Monsoon Rainfall (cm) over India and Neighbourhood Characteristics of Classification CHARACTERISTICS OF PRECIPITATION IN INDIA Annual rainfall(cm) over India Example 1. A lake has a water surface elevation of 102.30 m above datum at the beginning of a certain month. In that month the lake received an average inflow of 6.0 m3/s from surface runoff sources. In the same period the outflow from the lake had an average value of 6.5 m3/s. Further, in that month, the lake received a rainfall of 145 mm and the evaporation from the lake surface was estimated as 6.10 cm. write the water budget equation for the lake and calculate the water surface elevation of the lake at the end of the month. The average lake surface area can be taken as 5000 ha. Assume that there is no contribution to or from the groundwater storage.