Unit No. 6 Ground water recharge: Introduction, selection of recharge sites, recharging methods, spreading method, Induced recharge method, Recharge well method, sub-surface dams, waste water recharge, recharge by urban storm runoff, recharge through rain water harvesting. Project planning for water resources: Multipurpose projects, Inter basin water transfer and Inter state water disputes, Water resources planning through watershed management, Economic planning for domestic and industrial water supply.
Ground Water Recharge 1. Underground water is one of the important sources of water in urban areas. 2. With increasing urbanization, underground water has been indiscriminately exploited causing depletion in water table and water availability. 3. It is very evident from the number of failing bore wells / open wells that it is unsustainable to pump out water from wells without recharging the same from the rainwater. 4. To reverse the trend or to reduce the effect of over exploitation, ground water recharge needed.
Recharging of Underground Storage: 1. Artificial surface reservoir are constructed by building dam in order to store the surplus water, in the same manner, artificial underground reservoir are now a days developed by an artificial recharge, for storing the water. 2. Development of such a reservoir may be advantageous as compared to surface reservoir: 1. Much purer water can be obtained from a underground reservoir source. 2. No space is required for building such a reservoir. 3. Cost for recharging the aquifer may be less than the cost of the surface reservoirs. 4. The water loss in evaporation from an underground reservoir is much less than the water lost from a surface reservoir. 5. The raising of water table may help in building pressure barriers to prevent sea water incrustation in the coastal areas.
Criteria For Selection of Ground Water Recharge Sites:- 1. The recharge site should be such that quantity of leakage through it is a minimum. 2. The recharge sites should be such that the water stored in it is suitable for the purpose for which the project is undertaken. 3. The soil and rock mass at the site must not contain any objectionable minerals and salts. 4. The cost required should be as less as possible. 5. Select the sites such that it should have maximum storage capacity. 6. Sites should be free from earthquake zone.
Ground Water Recharge or Artificial Ground Water Recharge: 1. Artificial recharge of ground water basin is a method for increasing the natural supply of ground water by construction of certain artificial civil works. 2. The three methods which are generally adopted for ground water recharging are as below: a) Spreading Method:- spreading the water over the permeable surface by constructing bunds or earthen dykes which subsequently infiltrates to shallow aquifers. b) Recharge Well Method:- injecting the water into bore holes, called recharge wells. c) Induced Infiltration Method:- Increasing the water table gradient from a source of recharge. Wells are constructed near the river banks. The percolating water is collected in the well through radial collectors and is then discharged as recharge into a lower level aquifer for storage.
Ground Water Movements:- 1. Water table is generally not horizontal and has high and low points in it. Water moves inside the ground from the high points on the water table to the points lower down. Rate of movements depends on porous medium (permeability) and hydraulic gradient.
Rainwater Harvesting 1) To address the problem of water scarcity and effective conservation of rain water. 2) The process of collecting and storing rain water in a scientific and controlled manner for future use. 3) Rain water is collected from the roof top of a building, community, structures, landscapes, open fields, green parks, storm water drains, roads, pavement etc. and stored ready for re-use as required. 4) Collected water can be filtered and directly be put into a percolation pit or open well or dispersion trench to recharge the ground water. 5) It reduces runoff and flooding of storm drains. 6) collected water can be used for flushing toilets, general cleaning, garden irrigation and washing clothes.
1. Rain water is collected on rooftops. 2. This water is guided into overflow pipes. 3. These pipes connect to an underground tank.
RAIN WATER HARVESTING TECHNIQUES : There are two main techniques of rain water harvestings. Storage of rainwater on surface for future use. Recharge to ground water. The storage of rain water on surface is a traditional techniques and structures used were underground tanks, ponds, check dams, weirs etc. Recharge to ground water is a new concept of rain water harvesting and the structures generally used are :- Pits:- Recharge pits are constructed for recharging the shallow aquifer. These are constructed 1 to 2 m, wide and to 3 m. deep which are back filled with boulders, gravels, coarse sand. Trenches:- Trench may be 0.5 to 1 m. wide, 1 to 1.5m. deep and 10 to 20 m. long depending up availability of water. These are back filled with filter. materials. Dug wells:- Existing dug wells may be utilized as recharge structure and water should pass through filter media before putting into dug well. Hand pumps :- The existing hand pumps may be used for recharging the shallow/deep aquifers, if the availability of water is limited. Water should pass through filter media before diverting it into hand pumps.
Recharge wells :- Recharge wells of 100 to 300 mm. diameter are generally constructed for recharging the deeper aquifers and water is passed through filter media to avoid choking of recharge wells. Recharge Shafts :- For recharging the shallow aquifer which are located below clayey surface, recharge shafts of 0.5 to 3 m. diameter and 10 to 15 m. deep are constructed and back filled with boulders, gravels & coarse sand. Lateral shafts with bore wells :- For recharging the upper as well as deeper aquifers lateral shafts of 1.5 to 2 m. wide & 10 to 30 m. long depending upon availability of water with one or two bore wells are constructed. The lateral shafts is back filled with boulders, gravels & coarse sand. Spreading techniques :- When permeable strata starts from top then this technique is used. Spread the water in streams/nalas by making check dams, nala bunds, cement plugs, gabion structures or a percolation pond may be constructed.
Wastewater Recharge:- (Groundwater Recharge by Wastewater) 1) Lack of specific criteria & guidelines governing the artificial recharge of groundwater with recycled wastewater is currently hampering the implementation of large scale groundwater recharge operation. 2) Groundwater recharge with wastewater or reclaimed water and direct potable water reuse share many of the public health concerns encountered in drinking water withdrawn from polluted water source like river & reservoir. 3) Certain pretreatment is needed before groundwater recharge by wastewater.
Water resources project and the general planning includes: Planning arrangements for drinking water supply project and related data requirement Planning arrangements for irrigation water supply project and related data requirement Planning arrangements for hydropower generation project and related data requirement Planning arrangements for flood control project and related data requirement Investigations for data assessment for constructing water resource engineering structures Water availability computations Data collection for environment, socio-economic information. Data collection methods for topography, geology, rainfall and stream flow.
Consumptive & Non-consumptive Uses of water:- 1) When maximum portion of the water diverted for any purpose is consumed and is lost for further use, then it is called consumptive use for example, the use for irrigation is a consumptive use. 2) When water used for any purpose does not get consumed, it is called nonconsumptiveness. Hydropower generation, navigation, etc.
Multipurpose Water Resource Project:- 1) A multipurpose project may be defined as a project which is designed and operated to serve more than one purpose. 2) Project designed for single purpose but incidentally produces extra benefits for some other side purpose should not be called as a multipurpose project. 3) When two or more uses of water are combined together while designing a multipurpose project, increased benefits without a proportional increase in the cost may be obtained thus enhancing the economic justification of the project. 4) While planning for optimum utilization of our water resource it becomes absolutely necessary to make the maximum use of water with minimum cost in a unified and a co-ordinated manner and hence the multipurpose use of water becomes imperative.
Multipurpose Water Resource Project:- (Function or Purpose) 1) Irrigation 2) Flood control 3) Hydropower Generation 4) Water supply 5) Navigation 6) Fish & Life Development 7) Recreation, Sanitation, etc Damodar Valley Project Bhakra-Nangal Project The Hirakud Project The Kosi Project The Rihand Project The Chambal Project
Water Conservation measures comprises of the following :- 1) Water should be economically used. 2) Consumption of water per unit farm should be reduced. 3) Disposal of sewage in the water resources should be prevented. 4) Industrial consumption of water should be reduced. 5) Public should prevent wastage of water. 6) Multipurpose project. 7) Underground water reservoir. 8) Creation of reservoirs for storing the water 9) Prevention of losses 10) Improving use efficiency 11) Recycling and reuse of waste water 12) Price policy
National Water Policy National Water Policy is formulated by the Ministry of Water Resources of the Government of India to govern the planning and development of water resources and their optimum utilization. The first National Water Policy was adopted in September, 1987. It was reviewed and updated in 2002 and later in 2012. 1) It lays emphasis on need for national water framework law. 2) For essential health & hygiene and sustenance of ecology ensured. 3) ecological need of the river (low or no flows, small floods, large floods and flow variability) 4) A portion of river flows should be kept aside to meet ecological needs. 5) It recognizes the need to adapt to climate change scenario in planning and implementation of water resources projects.
Inter Basin Water Transfer: 1. Inter basin transfer or trans-basin diversion are man-made conveyance schemes which move water from one river basin where it is available, to another basin where water is less available or could be utilized better for human development. 2. The purpose of such designed schemes can be to improve water shortages in the receiving basin and to generate electricity, or both. 3. The first modern developments were undertaken in the 19th century in Australia, India and the United States.
Inter State River Dispute:- 1. Indian river run over a more than one state. States claims for water of their privilege. But when reservoir are constructed in one state, on the upstream side are major beneficiaries while those on downstream side may not get their share. 2. To overcome this central government constituted National Water Policy to divide water according to population of states through which rivers pass. 3. But in present scenario, some states started violating laws pointing out some drawbacks in sharing policy. This has given rise to inter state dispute. 4. Major prevailing disputes are: Karnataka-Tamilnadu over Cauvery-River Basin, Goa-Karnataka over Mandel-Mandoni Basin, Punjab-Haryana- Rajasthan-J&K over Sutlej-Beas-Ravi Water & Punjab-Haryana dispute for Sutlej-Yamuna Link. 5. Today supreme court has to play major role in settling those disputes.
Subsurface Dam:- 1. A system to store groundwater by a cutoff wall (dam body) set up across a ground water channel. 2. Similar to a surface dam in its function of water storage by a dam body but is different in the following area:- 1. A system to store groundwater 2. Storage in geological strata 3. A dam constructed underground 4. Water pumping is required Advantages:- Water storage without land submergence Prevention evaporation of reserved water Clean & safe water A stable & secure dam Does not exhaust water resources
Ground Water Quality:- Ground water quality depends upon following factors: 1. Infiltration 2. Rainfall characteristics 3. Soil characteristics 4. Soil cover 5. Porosity 6. Water bearing stratum 7. Ground water flow 8. Ground water yield 9. Permeability
Protection Measures (Ground Water Contamination): 1) Proper well construction can significantly improve water quality 2) Well location upstream/away from pit latrines, waste dumps and cemeteries 3) Concrete platforms around well with proper drainage 4) Animals must be kept away by a fence
Economics of Water Resources Planning:- 1) For any water resources project there are always some definite objectives which can be achieved in different manners. 2) For the same project there might be many alternatives. 3) Among these genrally the cheapest or most economic method is selected considering comparative merits and demrits of the different alternatives. 4) For the planning of any project firts of all the possible alternatives are proposed. 5) After comparing their merits and demerits each alternative is expressed in money units. 6) The capital expenditure & maintence cost should also be calculate for the proposal. Thus all the projects involve major sets of alternatives with many subordinate sets of alternatives in each major alternatives.
Ground water Provinces in India:- India is divided into 8 provinces for the purpose of study in ground water. 1) Precambrian Crystalline Provinces 2) Precambrian Sedimentary Provinces 3) Gondwana Sedimentary Provinces 4) Decan Trap Provinces 5) Cenozoic Sedimentary Provinces 6) Cenzoic Fault Basins 7) Ganga Brahmaputra Indus Alluvial Provinces 8) Himalaya Highland Provinces
Precambrian Crystalline Provinces:- It consists of penninsular India ie from southern tip to Delhi. Consists of Plutonic, Igneous & Metamorphic rocks. Precambrian Sedimentary Provinces:- Region of country are Raipur basin of MP, Western Rajasthan Basin, Cuddaph basin of AP, etc. Sedimentary formation contains sandstone, shale, limestone, etc. Gondwana Sedimentary Provinces:- Comprises patches of Gujrat, Rajasthan and coal belt of eastern India. Decan Trap Provinces:- Comprises almost entire state of Maharshtra & parts of Saurashtra in Gujrat, etc. Consists of volcanic products.
Text books: 1] Ojha, C.S.P., Berndtsson, R., and Bhunya, P., Engineering Hydrology, Oxford University Press 2] Raghunath H.M., Hydrology, New Age International Publishers. 3] Reddy R., Hydrology, Tata McGraw-Hill New Delhi. Reference books: 1] Linsley, R.K., Kohler, M.A. and Paulhas, Hydrology for Engineers, Tata McGraw- Hill Publishing Company Limited. 2] Todd, D.K., Ground Water Hydrology, John Wiley & Sons. 3] Subramnaya, K., Engineering Hydrology, Tata McGraw-Hill Publishing Company Limited. 4] Sharma R.K., Sharma T.K., Hydrology & Water Resources Engineering, Dhanpat Rai Publications.