The north-eastern region of Thailand, referred to as „Isan“, experiences the most extensive droughts when compared to the rest of the country. Increasing water demands due to population growth and agricultural development has resulted in more frequent and severe water shortages. It is expected that during the 21st century Global Climate Change will be putting more strain on the limited fresh water resources.
During droughts the, mostly rural, population are more reliant on already declining groundwater resources. While excessive groundwater extraction could leave residents without drinking water during a prolonged dry season, a dropping water table could also further increase the regions problems with salt water intrusion.
To aid in decision-making processes, when considering water resource management in Isan, the areas where the biggest changes in groundwater level are expected for the year 2050 and 2100 were identified. To account for the effects of climate change, delta changes derived from three climate models (GFDL-ESM2M, IPSL-CM5A-LR, MPI-ESM-MR) were imposed on meteorological observations. Subsequently, the expected change in groundwater recharge was calculated and used as an input for a one-layered steady-state finite-element groundwater model. The relative differences between the modelled historic and future periods were then calculated for two climate change scenarios (RCP 4.5 and 8.5) and two pumping scenarios.
The annual RCM climate modelling results show, although systematically underestimated and less so for extreme values, a similar distribution as the observations. A decrease in the hydraulic head is predicted for all scenarios at the end of the 21st century. While groundwater extraction exerts more influence locally, climate change causes a more evenly spread decline of the groundwater head over the entire north-east of Thailand. In general, taking into consideration the hydrological model’s limitations, the most remarkable changes in groundwater elevation are located the furthest from riparian areas and coincide with the location most effected by groundwater extraction. These areas, besides Buriram, are all situated in the Chi watershed and include for the most part the provinces of Chaiyaphum Mahasarakham, Roi Et and Nong Bua Lamphu.
With the already expected decline of groundwater head defined within this study throughout all of Isan because of climate change, a continued intensification of groundwater extraction could lead to an increase in saltwater intrusion and eventually the unavailability of the groundwater resources for domestic purposes. Because of its importance for the livelyhood of the region during water shortages, it is advised not to expand upon groundwater utilization for irrigational purposes, especially for those regions defined in this research to be most affected during the 21st century, to keep the resource available as a safeguard throughout periods of drought.