Groundwater Recharge Structures Dr. P. T. Hanamgond GSS College, Belgaum

INDIA’S LAND RESOURCE, IRRIGATION AND FOOD PRODUCTION India has 2% of world’s land, 4% of freshwater, 16% of population, and 10% of its cattle. Geographical area = 329 Mha of which 47% (142 Mha) is cultivated, 23% forested, 7% under non-agri use, 23% waste. Per capita availability of land 50 years ago was 0.9 ha, could be only ha in Out of cultivated area, 37% is irrigated which produces 55% food; 63% is rain-fed producing 45% of 200 M t of food.

Droughts, usually occur due to prolonged dry period, mainly due to less or no rainfall, over exploiting of water, unscientific irrigation, deforestation, loss of grasslands (overgrazing) etc.

Floods occur mainly due to- Heavy rainfall- Cloud bursts Breaching of dams/reservoirs Coastal flooding Melting of ice

Artificial recharge Augmentation of ground water reservoir by man made structures by using rain water. Rain Water Harvesting is deliberate collection and storage of rain water

Why Groundwater Recharge? Major causes for water scarcity Rainfall pattern Geomorphological set up Drainage Hydro geological factors Over exploitation Reclamation of land for settlement

Ideal conditions for artificial recharge to groundwater- 1.Adequate space for surface storage is not available especially in urban areas. 2.Water level is deep enough (>8m) and adequate subsurface storage is available. 3.Permeable strata is available at shallow/moderate depth. 4.Where adequate quantity of surface water is available for recharge to groundwater. 5.Groundwater quality is bad and our aim is to improve it. 6.Where there is possibility of intrusion of saline water especially in coastal region. 7.Where the evaporation rate is very high from surface water bodies. In other areas, rain water harvesting techniques may be adopted.

Rain water Harvesting a.Storage of rain water on surface for future use b.Recharge to ground water -Pits -Trenches -Dug wells -Hand pumps -Recharge wells -Recharge shafts -Lateral shafts with bore wells -Spreading techniques

Methods of Artificial Recharge a.Direct surface techniques. Flooding. Basins or percolation tanks. Stream augmentation. Ditch and furrow system. Over irrigation b.Direct subsurface techniques. Injection wells or Recharge wells. Recharge pits and shafts. Dug well recharge. Bore hole flooding. Natural openings,cavity filling c.Combination of Surface-Subsurface techniques. Basin or percolation tanks with pit shaft or wells d. Indirect Techniques. Induced recharge from surface water source.Aquifer modification

Rain Water Harvesting– Advantages 1. Provides self-sufficiency to water supply 2. Reduces the cost for pumping of ground water 3. Provides high quality water, soft and low in minerals 4. Improves the quality of ground water through dilution when recharged 5. Reduces soil erosion & flooding in urban areas 6.The rooftop rain water harvesting is less expensive & easy to construct, operate and maintain 7. In desert, RWH only relief 8. In saline or coastal areas & Islands, rain water provides good quality water

Benifits An ideal solution to water problems in areas having inadequate water resources The ground water level will rise Mitigates the effects of drought Reduces the runoff which chokes the storm water drains Flooding of roads and low land areas are reduced Quality of water improves Soil erosion will be reduced Saving of energy per well for lifting of ground water-a one meter rise in water level saves about 0.40 KWH of electricity.

Cost S.NoRecharge structureApproximate cost (in Rs) 1Recharge pit Recharge trench Recharge through hand pump Recharge through dug well Recharge well

Hill slope trenching/ Contour Bandhs

A forestation

Percolation Tanks

Recharge Pits/Wells

Water Distribution

Roof Water Storage

Lakes/Tanks desiltation

Rainwater harvesting Rainwater runoff from roofs is stored in tanks to be used inside buildings. Stormwater from streets and parks can be infiltrated or stored in ponds to provide water for trees, gardens and parks. Sand filters and constructed wetlands can be used for quality control. every drop counts 3. ESTs Storage

Storage of treated sewage Effluent from sewage treatment plants can be reused in surface waters as a source for urban water supply. Quality control is crucial. The use of effluent for recharging groundwater is possible. Soil Aquifer Treatment technology prevents pollution by pathogens, nutrients and other contaminants. every drop counts 3. ESTs Storage

Recharge Pond Water is recharged primarily to sinkholes

Bore well Recharging/Injection

Storage/Soak Pits

Check Dams/Bandhars

Water spreading to Salt pans, fishery/aqua culture ponds

Subsurface Dykes

By soil conservation measures 1- Peripheral and marginal bunds to harvest rain water & check soil erosion. 2- To check bank erosion and extension of gullies.

Cultural practices Ridges furrow method 1- Ridges and furrows are made across the slope of the field to harvest rain water.

68 1- Trench is made across the slope at the end of field to harvest rain water. Trenching

69 Recharging Through pit 1- Recharge pits on the bed of drains are natural drains are made to recharge ground water.

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71 Recharging through open well 1- Open well constructed near the tank to recharge ground water.

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