THE ROLE OF GROUNDWATER TO MITIGATE THE DROUGHT AND AS AN ADAPTATION TO CLIMATE CHANGE IN THE PHITSANULOK IRRIGATION PROJECT, IN THE NAN BASIN, THAILAND

Abstract

The Phitsanulok Irrigation Project is located in the Nan Basin of the Upper Central Plain of Thailand where farmers depended on both surface water and groundwater. Land use and climate changes are the important factors to determine the runoff from the watershed. The changes also affected to runoff volume/pattern to the dam operation and may cause flood and drought situations in the downstream area. Sirikit Dam is one of the biggest dams in Thailand which cover about 25 % of the runoff into the Central Plain where the Bangkok Capital is located. Though there is the Sirikit Dams storing water to be used during dry period but water allocation is limited and still caused water shortage during dry season. The study aims to determine the role of groundwater to mitigate the drought situation from the past and to study the groundwater use for adaptation to climate change in The Phitsanulok Irrigation Development Project. In this study, the relationship of recharge rate with climate data was developed in terms of precipitation, evapotranspiration, temperature and soil type under monthly time series data and the study found that there were in good relationship. Groundwater will take an important role to alleviate from the water shortage situations in climate change conditions when compared with the situations based on the existing water use pattern. The limit of ground water to alleviate water shortage will be 80 and 77 MCM/year in average, in near future and far future periods to keep water table drawn down in the safe manner even when the Sirikit’s reservoir operation rule is improved.