Numerical investigation of sustainable groundwater yields for the Wiang Pa Pao aquifer system in northern Thailand

Because of ongoing economic growth, the Kok River Basin in northern Thailand may suffer from near future water stress and its long-term sustainable groundwater yield has to be put into question. Based on a recent hydrogeological investigation of the Wiang Pa Pao aquifer system, which is one of the subsurface units within the Kok River Basin, a 3D groundwater model was set up to evaluate the sustainable groundwater yield for the near future. Steady-state and transient calibrations of the model were conducted for hydraulic conductivity, aquifer recharge, and storativity. The maximum allowable pumping rates to ensure that water levels in the aquifer do not fall below 20 m from the surface in the next 20 years were computed for various districts of the aquifer system. The results indicate that the present-day groundwater extraction rates may be exceeded by a factor of 100 during this time period before the sustainable yield constraint is violated