22-Assessment of forest influences on ground water regime.

Abstract

Researchers have been trying for past several decades to ascertain the hydrological importance of forests. As watershed experiments are generally long term and expensive, and need a high degree of trained manpower, most research evidence in this field comes from the temperate, industrialised countries. Yet even in developed countries role of forests as far as it affects hydrologic parameters in general and ground water regime in particular remains a matter of scientific investigation. The studies carried out so far regarding influences on ground water do not give coherent results. In forested watersheds on one hand, it is advocated that due to improved conditions of soil surface and soil structure the ground water regime would improve owing to better recharge conditions while on the other due to high rate of evapotranspiration of forests, the water table is considered to be adversely affected. Use of a mathematical modelling approach has been suggested in the present paper to study the influence of forests on ground water regime. The approach is based on a solution given by Hantush (1967) to find out position of water table in an unconfined aquifer with known values of recharge rate and aquifer parameters. Based on limited number of studies done on evapotranspiration and recharge rates in forested basin in the country, these values were assumed to find out effects of forests on water table regime. It was found that due to better recharge conditions the water table rose during rainy season but in non-rainy season the water table declined as a result of forests. The effects of forests were predominent only in and around forested region. There is a vast scope to further improve the results by using more realistic data.