UNIT-I. Reservoir Planning.pdf

College of Science and Technology CST Royal University of Bhutan FMH403 Hydraulic Structures and Water Power Engineering Leki Dorji A centre of excellence in science and technology enriched with GNH values ...

College of Science and Technology CST Royal University of Bhutan FMH403 Hydraulic Structures and Water Power Engineering Leki Dorji A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan Assessment Approach Mode of Sl. No. Nos. Marks Allocated Marks (%) Assessment 1 Term Test 1 10 Assignments/Case 2 1 15 Study Tour 3 Report/Presentatio 1 25 n Semester 5 Examination 1 50 Total Marks 5 100 A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan General Objective: The module aims to introduce the principles of design and applications of various hydraulics structures and also, cover the concepts of water power engineering and energy solutions. Students will also learn how to estimate the hydropower potential and the layout of hydropower components. The module is designed to enable participants to understand the concept of E-flow and conduct assessments in line with the methodology under the E-flow guideline. A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan Learning Outcomes: On completion of the module, students will be able to: 1. Evaluate the effect of sedimentation on the life of water retaining structures. 2. Estimate hydropower potential and reservoir capacity. 3. Carry out stability analysis of various types of dams. 4. Design the most appropriate type of spillways for different kinds of dam. 5. Identify the types of hydraulic jump and energy dissipators. 6. Carry out assessment of size and layout hydropower components. 7. Explain the concept of E-flow and its significance for water resource management; 8. Describe the applications of E-flow assessment and the legislative requirements of E-flow; 9. Explain the physical, chemical and biological components of river systems; A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan Subject Matters Part A: Hydraulic Structures 1. Reservoirs and Planning for Dam Reservoirs 2. Gravity Dams 3. Spillways 4. Water Conveyance: Part B: Hydropower Engineering 1. Introduction hydro- power 2. Load and Power studies 3. Fundamental components and methodologies of E-flow A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan Reading Lists Essential Reading Dandekar, M. M., & Sharma, K. N. (2013). Water Power Engineering. Vikas Publishing Company. Garg, S. K. (2003). Irrigation Engineering & Hydraulic Structures. Khanna Publishers. Modi, P. N. (2020). Irrigation Water Resources and Water Power Engineering. Standard Book Company. Williams, J. G., Moyle, P. B., Webb, J. A., & Kondolf, G. M. (2019). Environmental Flow Assessment: Methods and Applications. Wiley-Blackwell. Additional Reading Asawa, G. L. (2003). Irrigation Engineering. New Age International Publishers. Department of Hydropower & Power Systems, Ministry of Economic Affairs (2008). Bhutan Sustainable Hydropower Development Policy 2008 National Environment Commission, Royal Government of Bhutan. (2016) National Integrated Water Resources Management Plan, 2016 Date: May 2024 A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan UNIT-I: Reservoir and dam planning Leki Dorji A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan Reservoir and dam planning Definition & Types Reservoirs: Is a manmade lake or large fresh body lake of water. It is artificial and made by humans while lakes are naturally occurring bodies of water. Three types of Reservoirs: Valley dammed, Bank side, services Valley dammed: created in valleys in between mountains A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan Reservoir and dam planning The multipurpose dam is a very important project for developing countries, because the population receives domestic and economic benefits from a single investment. Dams and reservoirs are crucial for the storage of water, whether it is for potable water supply, flood alleviation, hydro-electricity, or irrigation The development of a new dam or reservoir, the final choice of site and design of the structure will depend not only on the topography but also on the geology, seismic activity and environmental impact. A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan Reservoir and dam planning What is a dam? A dam is a man-made structure built across a river. Most dams are built to control river flow, improve navigation, and regulate flooding. However, some dams are built to produce hydroelectric power.. Hydroelectric power is produced as water passes through a dam, and into a river below. The more water that passes through a dam, the more energy is produced. Once a dam is built, an artificial man-made lake is created behind the dam. Electricity is produced by a device called a turbine. Turbines contain metal coils surrounded by magnets. When the magnets spin over the metal coils, electricity is produced. Turbines are located inside power house. The falling water spins the magnets. A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan Reservoir and dam planning The purposes of dams Among the single purpose dams, 48 % are for irrigation, 17% for hydropower (production of electricity), 13% for water supply , 10% for flood control, 5% for recreation and less than 1% for navigation and fish farming. 1. Irrigation: 2. Hydropower: 3. Water supply for domestic and industrial use: 4. Inland navigation & Recreational 5. Flood control A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan IRRIGATION Irrigation water can be stored in reservoirs during the rainy season, then in the drier seasons it can be released from the reservoir and distributed over the land through a system of canals. Usually, the water flows under the influence of gravity to the areas requiring it, or the water can be pumped out of the canals onto the land. A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan Hydropower Reservoirs can be used to store water to feed hydroelectric power stations. The reservoir water is stored at a higher level than the turbines, which are housed in a power station. A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan Inland navigation & Recreactional The construction of a dam across a river forms a reservoir that raises the water level upstream, stores the water, and slows down its rate of flow. This improves the navigation conditions upstream of the dam for ships and boats. A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan Water Supply and Domestic Use dam is a barrier that impounds water or underground streams. The water from reservoirs must be cleaned before it is used. This is done at a water treatment works. Chemicals are added to help remove unwanted naturally occurring mineral particles and harmful bacteria. Dirt and other small particles are usually removed by filtering the water through beds of sand and gravel A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan Inland navigation & Recreactional Many large dams have flood-control reservations in which the level of a reservoir must be kept below a certain elevation before the onset of the rainy/summer melt season to allow a certain amount of space in which floodwaters can fill A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan Storage zones of reservoir The reservoir protection zones are composed of four protection areas: 4 3 1. an Immediate Protection Zone 2 2. a Close Protection Zone 1 3. a Distant Protection Zone 4. a Riparian Protection Strip along all DAM perennial or temporary rivers A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan Storage zones of reservoir 1. THE IMMEDIATE PROTECTION ZONE (IPZ) This zone concerns the immediate environment of the pumping installations and equipment which are generally near to the dam of the reservoir. The goal of this perimeter is to: 1. forbid access to the pumping point and to the treatment or pumping station ; 2. prevent damages on structures ; 3. prevent direct voluntary or involuntary introduction of pollutants in the water ; 4. protect the pumping zone from direct runoff and risk of pollutant spill from the banks. A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan Storage zones of reservoir 2. THE CLOSE PROTECTION ZONE (CPZ) The goal of the CPZ is to keep the reservoir and the rivers that feed into it away from point and non-point source pollution, accidental or non-accidental pollution which can be driven to them directly or by surface or subsurface runoff. Delineation: The delineation of the CPZ includes the immediate catchment area of the reservoir and the rivers whose flow contribution is considered as significant. A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan Storage zones of reservoir 3. THE DISTANT PROTECTION ZONE (DPZ) This zone reinforces the Close Protection Zone. Delineation: Considering the very short time of concentration of the reservoir watersheds, the Distant Protection Zone is defined as the whole watershed minus the Immediate and Close protection Zones. In the DPZ, the administration pays special attention to the major sources and risks of pollution and takes preventive actions A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan Storage zones of reservoir 4. THE RIPARIAN PROTECTION STRIP The goal of the Riparian Protection Strip is to preserve: 1. fauna and flora species ; 2. the rivers away from direct pollution due to activities close to the river. Delineation: along all the temporary or perennial river reaches in the reservoir’s catchment area as these are defined in the Cadastral maps a Riparian Protection Strip of 10 meters is delineated on each side of the stream axis. The RPS should be kept free of any construction or potential polluting activity or equipment and the vegetation should be maintained at its maximum possible natural status. A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan Storage reservoirs location selections 1. Existence of suitable dam site: The shortest dam to pond the requisite volume of storage is the best. This would be possible if the rivers flow through a narrow gorge and rapidly widens the upstream side. 2. The quantity of water available: It should be sufficient to meet all the demands throughout the year. This would depend the rainfall, run off and the catchment area 3. Distance and elevation of the reservoir with reference the point of distribution. A longer distance means greater of conduits while proper elevation of the reservoirs ensures adequate supplies through gravity A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan Storage reservoirs location selections 4. Density and distribution of population over the catchment area: It should be small density of population above uptstream of reservoirs 5. Existence of towns, highways , railway yards and other cultivation areas: These should excluded from the submerged area of reservoir. 4. Geological conditions of storage basin: IF the rocks are deeply fissured, there will considerable loss or percolate the water A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan Storage zone Reservoir storage zone A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan These specific levels and parts are generally defined as follows: Full Reservoir Level (FRL): It is the level corresponding to the storage which includes both inactive and active storages and also the flood storage this is the highest reservoir level that can be maintained without spillway discharge or without passing water downstream through sluice ways. Minimum Drawdown Level (MDDL): It is the level below which the reservoir will not be drawn down so as to maintain a minimum head required in power projects. Dead Storage Level (DSL): Below the level, there are no outlets to drain the water in the reservoir by gravity. A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan These specific levels and parts are generally defined as follows: Maximum Water Level (MWL): This is the water level that is ever likely to be attained during the passage of the design flood. It depends upon the specified initial reservoir level and the spillway gate operation rule. This level is also called sometimes as the Highest Reservoir Level or the Highest Flood Level. Live storage: This is the storage available for the intended purpose between Full Supply Level and the Invert Level of the lowest discharge outlet. The Full Supply Level is normally that level above which over spill to waste would take place.. A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan Storage zone Reservoir storage zone A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan Storage zone Reservoir storage zone Normal pool level: is the maximum elevation to which the reservoir surface will rise during ordinary operating conditions. It is determined by the elevation of the spillway crest or the top of the spillway gates. Minimum pool level: is the lowest elevation to which the pool is to be drawn under normal conditions. This level may be fixed by the elevation of lowest outlet in the dam or, in the case of hydroelectric reservoirs, by conditions of operating efficiency for turbines Dead Storage: is the water held below minimum pool level. A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan Storage zone Reservoir storage zone Useful Storage: is the storage volume between the minimum and normal pool levels. For multipurpose reservoirs in accordance with adopted plan of operation, the useful storage may be subdivided into: i. Conservation storage, ii. Flood mitigation storage. A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan Silt / Sedimentation zones ▪ The space occupied by the sediment in the reservoir can be divided into separate zones. ▪ A schematic diagram showing these zones is illustrated in Figure A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan Freeboard: o It is the margin kept for safety between the level at which the dam would be overtopped and the maximum water level. o This is required to allow for settlement of the dam, ✓ for wave run up above still water level and for unforeseen rises in water level, ✓ because of surges resulting from landslides into the reservoir from the peripheral hills, earthquakes or unforeseen floods or operational deficiencies. A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan PLANNING OF RESERVOIRS The first step in planning the construction of a reservoir with the help of a dam is -----for the decision makers to be sure of the needs and purposes for which the reservoir is going to be built together with the known constraints (including financial), desired benefits. There may be social constraints, for examples people’s activism may not allow a reservoir to be built up to the desired level or even the submergence of good agricultural level may be a constraint Some times, the construction of a dam may be done that is labour intensive and using local materials, which helps the community for whom the dam is being built A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan PLANNING OF RESERVOIRS The second step is the assembly of all relevant existing information, which includes the following: Reports of any previous investigations and studies, if any. Reports on projects similar to that proposed which have already been constructed in the region. A geographical information system (GIS) for the area of interest may be created using a base survey map of the region. Topographical data in the form of maps and satellite pictures, which may be integrated within the GIS. Geological data in the form of maps and borehole logs, along with the values of relevant parameters. Seismic activity data of the region that includes recorded peak accelerations or ground motion record. A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan PLANNING OF RESERVOIRS The second step is the assembly of all relevant existing information, which includes the following: Meteorological and hydrological data -available parameters like rainfall, atmospheric and water temperatures, evaporation, humidity, wind speed, hours of sunshine, river flows, river levels, sediment concentration in rivers, etc. For water supply projects, data on population and future population growth based on some acceptable forecast method, industrial water requirement and probable future industrial development. For irrigation projects, data on soils in the project area and on the crops already grown, including water requirement for the crops. For hydropower projects, data on past demand and forecasts of future public and industrial demand for power and energy; data on existing transmission systems, including transmission voltage and capacity. A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan PLANNING OF RESERVOIRS The second step is the assembly of all relevant existing information, which includes the following: Data on flora and fauna in the project and on the fish in the rivers and lakes, including data on their migratory and breeding habits. Data on tourism and recreational use of rivers and lakes and how this may be encouraged on completion of the proposed reservoir. A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan PLANNING OF RESERVOIRS However, there are other data that decides the following: Dam RBL 2620 m 1. Determine the volume of the reservoir and the dam height. Dam top 2660 m 2. Approximate the size of the spillway and at what elevation the Dam height 40 from RBL m crest level of the spillway be located? Locate such as MDDL, FRL & MWL Surface area 249,446 m2 3. How many and at what levels sluices be provided and they Dam Height 40 m should be of what sizes?- Literature reviews Volume 9.98 MCM (select one location in the Google earth map, work in the groups -5 students in a group) A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan Effect of sedimentation in planning of reservoirs It is important to note that storage reservoirs built across rivers and streams loose their capacity on account of deposition of sediment. o This deposition which takes place progressively in time reduces the active capacity of the reservoir to provide the outputs of water through passage of time. o Accumulation of sediment at or near the dam may interfere with the future functioning of water intakes and hence affects decisions regarding location and height of various outlets. o It may also result in greater inflow into canals / water conveyance systems drawing water from the reservoir. o Problems of rise in flood levels in the head reaches and unsightly deposition of sediment from recreation point may be reduced in due course of time. A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan Effect of sedimentation in planning of reservoirs While planning a reservoir normally combination of following two consists of: 1. Performance Assessment (Simulation) Studies with varying rate of sedimentation. /using empirical Formula 2. To observe that Likely effects of sedimentation at dam face. The steps to be followed for performance assessment studies with varying rates of sedimentation are as follows: a. Estimation of annual sediment yields into the reservoir or the average annual sediment yield and of trap efficiency expected. b. Distribution of sediment within reservoir to obtain a sediment elevation and capacity curve at any appropriate time. c. Simulation studies with varying rates of sedimentation. d. Assessment of effect of sedimentation. A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan Geological explorations for reservoir sites Though a dam is constructed to build a reservoir, a reservoir has a large area of spread and contained in a big chunk of the river valley upstream of the dam. Hence, while identifying a suitable site for a proposed dam, it is of paramount importance that the proposed reservoir site is also thoroughly investigated and explored. The basis of planning for such explorations is to have a rapid economical and dependable pre- investment evaluation of subsurface conditions. It is also necessary that a degree of uniformity be followed while carrying out subsurface explorations so that the frame of reference of the investigation covers all requisite aspects A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan Geological explorations for reservoir sites Bureau of Indian Standards has brought out a code IS: 13216 - 1991 “Code of practice for geological exploration for reservoir sites”, the following aspects of the reservoirs have to be properly investigated 1. Water tightness of the basins 2. Stability of the reservoir rim Assign-I, Describe briefly, how these 3. Availability of construction material in the reservoir area aspects will affect the 4. Condition of Silting construction of Dams/Reservoirs 5. Direct and indirect submergence of economic mineral wealth 6. Seismo-techtonics These aspects are determined through investigations carried out by surface and subsurface exploration of proposed basin during the reconnaissance, preliminary investigation, detailed investigation, construction and post-construction stages of the project A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan Geological explorations for reservoir sites The two basic stages of investigation: 1. Reconnaissance and 2. Preliminary investigations Reconnaissance: (MAPS) o the available geological maps on 1:50,000 or 1: 250,000 scales may be made use of photo geological interpretation of aerial photographs of the area o If a geological map of the area is not available, a traverse geological map should be prepared at this stage preferably using the aerial photos as base maps o A topographical index map on 1: 50 000 scales should be used at this stage to delineate the areas which would require detailed study, A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan Geological explorations for reservoir sites Reconnaissance: (Objectives) 1. To prevent an undesirable amount of leakage from the reservoir, the likely zones of such leakage, across the divide of the reservoir should be identified at this stage of investigation 2. Major unstable zones, particularly in the vicinity of the dam in tight gorges, should be identified at this stage for carrying out detailed investigations for the stability of the reservoir rim. 3. The locations for suitable construction material available in the reservoir area should be pin pointed at this stage ------so that after detailed surveys such materials can be exploited for proper utilization during the construction stage prior to impounding of reservoir. A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan PHPA-I- Geological Conditions A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan Geological explorations for reservoir sites Reconnaissance: (Objectives) 4. To the major geological formations and the ecological set up should be recognized at this stage to enable a more accurate estimation of the rate of silting of the reservoir investigation(90% of the catchment of storage dam project is composed of igneous and metamorphic rocks and is likely to yield a relatively low sediment rate) 5. Necessary that the economic mineral deposits, which are likely to be adversely affected by the reservoir area, are identified at this stage 6. It is, therefore, necessary to undertake the regional seismotechtonic study of the project area. The faults having active seismic status should be delineated at this stage. (Impoundment of a reservoir sometimes results in an increase of seismic activity) A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan Geological explorations for reservoir sites Preliminary Investigation ❖ On the basis of studies carried out during the reconnaissance stage it should be possible to o estimate the extent of exploration that may be required during the preliminary stage of investigation including the total number of holes required to be drilled and o The total number and depth of pits, trenches and drifts as also the extent of geophysical surveys which may be necessary (For exploration by pits, trenches, drifts and shafts guidelines laid down in IS 4453: 1980 Name of IS code should be followed) o The potential zones of leakage from the reservoir and the lateral extent of various features, such as extent of Aeolian sand deposits, glacial till, land slides, major dislocations or pervious and cavernous formations running across should be delineated on a scale of 1: 50000. A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan Fixing the capacity of the reservoirs Once it is decided to build a reservoir on a river by constructing a dam across it, it is necessary to arrive at a suitable design capacity of the reservoir, the reservoir storage generally consists of three main parts which may be broadly classified as: 1. Inactive storage including dead storage 2. Active or conservation storage, and 3. Flood and surcharge storage. In general, these storage capacities have to be designed based on certain specified considerations, Indian Standard codes:IS:5477 Fixing the capacities of reservoirs- Methods (Part1):1999 General requirements (Part 2): 1994 Dead storage Assignments-Describe briefly and (Part 3): 1969 Live storage design (Part 4): 1911 Flood storage a reservoir using part 1 to 4 A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan Fixing the capacity of the reservoirs The data and information required for fixing the various component of design capacity of a reservoirs: 1. Precipitation, runoff, silt record available in the region 2. Erodibility of catchment upstream of reservoir for estimating sediment yield 3. Area capacity curves at proposed station 4. Trap efficiency 5. Losses in reservoirs 6. Water demand from reservoir for different uses. 7. Committed and future upstream uses; 8. Criteria for assessing the success of the project; 9. Density current aspects and location of outlets; 10. Data required for economic analysis; and Assignments -I-Explain each of The Component in detail. 11. Data on engineering and geological aspects. A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan Control of sedimentation in reservoirs There are different techniques of controlling sedimentation in reservoirs which may broadly be classified as follows: 1. Adequate design of reservoir 2. Control of sediment inflow 3. Control of sediment deposition 4. Removal of deposited sediment. Design of reservoirs The capacity of reservoirs is governed by a number of factors which are covered in IS: 5477 (Parts 1 to 4) 1. The sediment yield which depends on the topographical, geological and geo- morphological set up, meteorological factors, land use/land cover, intercepting tanks, etc; 2. Sediment delivery characteristics of the channel system; A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan Control of sedimentation in reservoirs Control of sediment inflow There are many methods for controlling sediment inflows and they can be divided as under: 1. Watershed management/soil conservation measures to check production and transport of sediment in the catchment area. 2. Preventive measures to check inflow of sediment into the reservoir. The soil conservation measures are further sub-divided as: a) Engineering b) Agronomy, and c) Forestry. Example: The engineering methods include: 1. Use of check dams formed by building small barriers or dykes across stream channels. 2. Contour bounding and trenching; 3. Gully plugging; 4. Bank protection. A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan Removal of deposited sediment The removal of sediment deposits may be accomplished by a variety of mechanical and hydraulic or methods, o such as excavation, o dredging, o siphoning, o draining, o flushing, o flood sluicing, and o sluicing aided by such measures as hydraulic or mechanical agitation or blasting of the sediment A centre of excellence in science and technology enriched with GNH values  College of Science and Technology CST Royal University of Bhutan Thank you A centre of excellence in science and technology enriched with GNH values