Assessment of Optimum Yield of Groundwater Withdrawal in the Yogyakarta City, Indonesia

Abstract

The high demand of clean water supply and groundwater usages in Yogyakarta City, Indonesia has caused the lowering of groundwater table of about 3 m in average since 1984. This condition is caused by the increase number of groundwater pumping in this city relate to the rising of the urban population, economics condition, education and cultural activities, change of land use and increase number of hotels on this famous tourism city in Indonesia. Therefore, it became necessary to assess the optimum yield from the groundwater system beneath this city which can still preserve the recent level of shallow groundwater. This is important because most of the people in this city depends their daily water supply from shallow dug well. In order to assess the safe yield, a groundwater modeling is conducted. The data used on this modeling was taken from previous research and also primary data collected during this research such as; aquifer geometry, aquifer characteristics, shallow groundwater level, water usage/pumping wells discharge, river discharge and surface water level, and climate data. Prediction of the impact of groundwater pumping was made by increasing the water usage/pumping wells discharge on several scenarios. The result of this modeling shows that the optimum yield of the aquifer beneath Yogyakarta City area is about 125,000 m3/day. Keywords: Optimum yield, groundwater usage, groundwater table, pumping, urban population, shallow dug well.

Groundwater Flow Modeling in the Malioboro, Yogyakarta, Indonesia

“…According to previous research (Putra, 2003, andPutra et al, 2013) with new pumping test data of bore holes, theupper aquifer layer has hydraulic conductivity value of about 7.8 to 90 m/day. Meanwhile, hydraulic conductivity of the theloweraquiferis about 1.1 m/day.…”

“…Therefore, excessive pumping can threaten the groundwater condition in the study area. Previous regional groundwater flow model conducted by Putra et al (2013), reveals that with the pumping rate of totally 125000 m 3 /day in the whole Yogyakarta City area, will cause groundwater table to be decrease to about 3 m.…”

Groundwater Flow Modeling at Sejorong Watershed, Sumbawa,West Nusa Tenggara, Indonesia

“…Where, P : Precipitation (mm/year) ET r : Real evapotranspiration (mm/year) R o : Runoff (mm/year) Evapotranspiration is estimated based on the Turc (1954) equation (Putra et al 2013), as below:…”

“…Where, ET r : Evapotranspiration (mm/year) P : 10-year average rainfall (mm/year) T m : Temperature ( • C) and runoff is calculated based on the formula below (Putra et al, 2013 4. After data is collected, evaluation is done to understand the natural groundwater system including flow and water balance and followed by the development of the conceptual groundwater model, discretization of finite differene model area, inputing parameter, running model, model calibration and then finally conduct particle tracking model on calibrated groundwater flow model.…”

Mapping the Potential Liquefaction Area in Yogyakarta City Based on Ground Shear Strain Data

“…In the eastern part of Yogyakarta city, there is an earthquake source associated with the Opak fault that can be a source of ground shaking. This area is also dominated by the thick volcanic sediment from Merapi Volcano composed of tuff, ash, breccia, agglomerate, and lava flows [7] that can strengthen earthquake shaking. The groundwater depth in this area is also very shallow which range between 2.1 -12.7 m [8].…”