Indirect method

Induced recharge

It is an indirect method of artificial recharge. In this method water is pumped from the aquifer hydraulically connected to the surface water sources like stream, river or lake. Due to pumping, a reverse gradient is formed and water from the surface water source enters into the aquifer and thus the aquifer is recharged . This method is good, especially when quality of the surface water is poor. The filtration of surface water through soil strata removes the impurities of the water. Thus the quality of the water receives in the wells is much better than the surface water.

Aquifer modification method

This is also an indirect method of artificial recharge. In this method, some techniques are used to change the aquifer characteristic so that aquifer can store more water and also can transmit more water. After application of these techniques, more recharge takes place under natural condition as well as under artificial condition. The most commonly used techniques are, bore blasting method, hydro-fracturing method, jacket well techniques, fracture seal cementation and pressure injection grouting, etc.

1.  Bore blasting method

This method is used to increase the fracture porosity of an aquifer. Shallow bore wells are drilled in the area where fracture porosity of the aquifer is planned to increase. These bore holes are blasted with the help of explosive which creates fracture porosity in the aquifer.

2.  Hydro-fracturing method

Hydro-fracturing is used to improve the yield of a bore well. In this technique, water is injected at a very high pressure to widening the existing fracture of the rock. The high pressure injection of water also helps in removing of clogging, creates interconnection between the fractures, and extends the existing length of the old fracture. The high pressure injection also creates new fracture in the rock strata. As a result of these, the water storing and transmitting capacity of the strata increases.

3.  Jacket well techniques

Jacket well technique is used to increase the yield of a dug well. In this method, the effective diameter of the well is increased by drilling small diameter bores around the well in a circular pattern.

4.  Fracture seal cementation and pressure injection grouting

This technique is used to control the outflow from an aquifer. Cement slurry is injected into the aquifer using mechanical means or manually near to the aquifer outlet like spring, etc. The injection of cement slurry helps in reducing the fracture porosity of the aquifer near the outlet which will eventually reduce the outflow from the aquifer.