Estimation Of Natural Ground Water Recharge

INTRODUCTION

Ground water recharge may be explained as the process where by the amount of water

present in or flowing through the interstices of the sub-soil increases by natural or artificial means

TYPES OF ESTIMATION METHODS

¢ Physical methods use the principles of soil physics to estimate recharge. The direct physical methods are those that attempt to actually measure the volume of water passing below the root zone.

¢ Chemical methods utilize the presence of relatively inert water-soluble substances, such as an isotopic tracer or chloride.

¢ Numerical Models

Recharge can be estimated using numerical methods, using such codes as HELP, UNSAT-H, SHAW, WEAP, and MIKE SHE.

RECHARGE ESTIMATION TECHNIQUES

SOIL WATER BALANCE METHOD

¢In hydrology, a water balance equation can be used to describe the flow of water in and out of a system.

ZERO FLUX PLANE METHOD

¢The zero flux plane method relies on the location of a plane of zero hydraulic gradient in the soil profile.

Ground water level fluctuation method

¢This is an indirect method of deducing the recharge from the fluctuation of the water table.

CONCLUSION

¢ While estimating natural ground water recharge, it is essential to have a good idea of the different recharge mechanisms and their importance in the study area.

¢ Choice of methods should also be guided by the objectives of the study, available data and the possibilities to get supplementary data.