Techniques of Rain Water Harvesting to Increase Ground Water Levels

Topics: Hydrology, Groundwater, Water Pages: 46 (1626 words) Published: September 15, 2010

Scientist ‘D’ Central Ground Water Board Western Region, Jaipur

Rain water harvesting and Artificial recharge of ground water Rainwater harvesting is the technique of collection

and storage of rain water at surface or in subsurface
aquifer, before it is lost as surface run off or as

The artificial recharge to ground water is a process by which the ground water reservoir is augmented at a rate exceeding that under natural conditions of replenishment utilizing suitable civil construction techniques.

Identification of Area
•Areas where availability of ground water is inadequate in lean months. •Areas where groundwater levels are declining on regular basis. •Areas where salinity ingress is taking place.

Basic requirements for artificial recharge of ground water are: • Availability of non-committed surplus monsoon run off in space and time. • Identification of suitable hydrogeological environment and sites for creating sub-surface reservoir through cost-effective artificial recharge techniques.

Scientific Inputs

 

Hydrometeorological Studies
Hydrological Studies Soil Infiltration Studies

 

Hydrogeological Studies
Geophysical Studies Chemical Quality of Source Water

Assessment of sub-surface storage space for artificial recharge of ground water The sub surface storage space for artificial recharge in terms of volume of water which can be accommodated is estimated by taking into account the area of potential zone, depth to water below 3 m ground level and specific yield of the formation.


Artificial Recharge Techniques
Similar to the variations in hydrogeological frame work, the artificial recharge techniques too vary widely. The artificial recharge techniques can be broadly categorised as follows:

A. Direct surface techniques

• • • • Flooding Basins or percolation tanks Stream augmentation Ditch and furrow system Over irrigation

B . Direct sub surface techniques • • • • • Injection well or recharge well Recharge pit and shaft Dug well recharge Bore hole flooding Natural openings, cavity fillings

C. Combination surface & sub-surface techniques

• •

Basin or percolation tanks with pit shaft or wells.

D. Indirect Techniques Induced recharge from surface water source Aquifer modification

Ditch and Furrow Method
In areas with undulating topography, water from stream or canal is diverted to shallow, flat bottomed and closely spaced ditches or furrows to provide maximum water contact area for recharge. The water contact area seldom exceeds 10 percent of the total recharge area. Generally three patterns of ditch and furrow system are adopted.

Lateral Ditch Pattern Dendritic Pattern Contour Pattern

Site Characteristics and Design Guidelines
(a) Although this method is adaptable to irregular terrain. the water contact area seldom exceeds 10 percent of the total recharge area.


Ditches should have slope to maintain flow velocity and minimum deposition of sediments. Ditches should be shallow, flat-bottomed, and closely spaced to obtain maximum water contact area. Width of 0.3 to 1.8 m. are typical. A collecting ditch to convey the excess water back to the main stream channel should be provided.



Percolation Tanks (PT) / Spreading Basin
• These are the most prevalent structures in Rajasthan as a measure to recharge the groundwater reservoir both in alluvial as well as in hard rock formations.

Percolation tanks be normally constructed on second
to third order stream since the catchment so also the submergence area would be smaller.

The submergence area should be in uncultivable land as far as possible.

Percolation tank be located on highly fractured and
weathered rock for speedy recharge. In case of alluvium, the...
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