Pemanfaatan air tanah dengan memperhatikan aspek lingkungan yang berkelanjutan=Goundwater usage with respect to environmental sustainability

Groundwater usage has been very intensive around Sleman, which is in the lower slope and foot part of Merapi volcano (Sleman), DIY, especially by deep wells pumping. The research objective is to find out an alternative of sustainable groundwater usage (withdrawals) in the study area. Well withdrawals are being evaluated, then an alternative of safe-yield-withdrawal is being proposed. The research mostly used secondary data. Field observations were being conducted to estimate several river heads, conductance, and condition of some deep wells in Merapi aquifer, with emphasis on the study area. The compiled data was then being used for groundwater flow simulation using MODFLOW interface, steady state condition, in GMS (Groundwater Modeling System) v3.1 software. The result showed that the average withdrawal in the study area did not exceed safe yield. But still, caution to use water is needed because data being used in the simulation is scarce, Different well withdrawals simulation showed that the decrease of water level in the Sleman area were negligiblebut in other regions, that are around the city of Yogyakarta and around Bantul regency, the surrounding area of wells dried up. So it can be concluded that with the given simulation condition, a well withdrawal should not exceed recharge in the whole area devided by all wells in the area. With the asumption of 39 wells being simulated, steady state condition, it is proposed that a well withdrawal in the Sleman area should not exceed 28968 m3/ day for groundwater sustainability, with given percolation asumption of 0.0025 m/ day and average hydraulic conductivity of 30-100 m/ day. Keywords : groundwater, simulation, GMS v3.1, withdrawa