Groundwater Flow Modelling In A River Basin

摘要

Groundwater is an important source of water for drinking, irrigation and industrial purposes. To maintain a sustainable agricultural production and to arrest the depletion of water table, there is a need for micro level study of groundwater potential. In this work an attempt has been made to estimate the amount of groundwater for the Gundar river basin, which can be used to plan a suitable usage of groundwater. Visual MODFLOW was used for groundwater flow simulation in the study. The model when applied to the study area showed the permissible error of ± 10 - 20% in 87.3% of computed values from the actual values of wellheads. The results showed that the flow direction was more or less coincided with the general slope and there was an inflow and outflow across to western and eastern boundaries. The coastal alluvial formations showed the intrusion of seawater into inland freshwater aquifers. The depth of groundwater varied from 23.0 m (riverside) to 29.0 m (highest elevated areas). As frequent monsoon failures are quite common in these areas, an attempt was made to assess the groundwater potential under conditions of 25%, 50%, 75% and 100% failure of northeast monsoon with the year July 2001 to June 2002 as reference point. A 25% failure reduced the groundwater table to 26 m from 23 m, a reduction of 13.04% from the reference year (July 2001 - June 2002). When the failures were 50% and 75%, the corresponding values were 29 and 30 m viz., a reduction of 26% and 30% respectively. If there is no rain, then the nearest water table depth dropped to 30 to 40 m from the ground level.