Development of Model for Simulation Study of Groundwater under Affection of Various Surface Condition in Cidanau Watershed

Abstract

The groundwater model was developed adopting USGS Modflow model, a three dimensional ground water flow modular model that could be readily modified. The simulation was conducted for the caldera of Cidanau watershed, the flat area where the natural reserve of Rawa Danau swamp lays. The area was assumed to have only one soil layer with uniform properties of soil hydraulic conductivity, specific storage, specific yield and porosity of 0.0001 mls, 0.00011m, 0.2 and 0.2. Digital Elevation Data (DEM)'was fed to the software to generate the thickness and the elevation of the ground layer. Only 6 rivers were used for boundary condition, and as well as the swamp their water level were assumed constant along the simulation for simplification. There are 6 land uses taken into account which area paddy field, bare field, plantation, residential, swamp forest and upland field. The simulation was conducted in daily time step for 90 days with initial groundwater level at 2 meter depth below the surface. Since precipitation has not yet been taken into account, alteration of the groundwater was only happen by mean of evaporation, percolation and leakages from river and swamp. The simulation shows the largest decreased of groundwater level occurs in bare field, and in paddy field the level seems to be preserved.