Ground Water Modelling for Rain Water Harvesting System

Groundwater is the largest reservoir of fresh water on the planet earth. In many areas of developing countries, increasing groundwater use has led to depleted aquifers. Artificial groundwater recharge using rain water is a basic concept for the sustainable management of vital freshwater resources. This study aimed to develop a methodology to assess the impact of RWH for an urban aquifer. A groundwater model is developed for simulating the effect of RWH and to predict the future scenario. The period of Jan 1995 to December 2000 is used for model calibration process and the period of Jan 2001 to January 2003 is used for validation process. The model is simulated in transient condition for a time interval of 9 years from January 2004 to May 2012. The calibrated model (pre RWH period that is influenced by natural recharge only) is used to simulate the regional groundwater head and it is compared with the observed data (that is influenced by both natural and artificial recharges (due to RWH implementation in the year 2003)) of 15 wells. The difference of observed head and simulated head indicates the impact of RWH. Prediction scenario on the effect of artificial recharge is carried out from 2012 to 2025. There is a difference of 2 m water table in each scenario for 20% increase or decrease in pumping and recharge rate. The impact of RWH simulated through modeling shows the improvement of water table. But, the results from the future prediction scenarios indicate that water table will go down if pumping is increased and rainfall is decreased. Hence, there is a necessity to educate the society for proper usage of ground water and maintaining the RWH structures.