Abstract
The floodplain in Phichit province, Thailand always has flood in rainy season and water lacking in dry season. This area is a major recharge area of Thailand and farmers set many wells for drawing groundwater, because of insufficient surface water during two times of paddy crop and unavailable irrigation systems. This causes severe decreasing of groundwater level with no sign of recovery. In inundation area, the average flood depth is about 2m and has duration 1-2 month. The authors set up the observation systems in this study area to monitor their daily change in groundwater level, river water level, and rainfall. Flood water in this area recharges shallow aquifer and continuously flows down to deep aquifers. This paper presents the simulation of groundwater budget in this area based on the Tank model concept using data in 2002-2004. The results show that recharge through ground surface by flood is about 55% of annual recharge and 73% of annual recharge flow down to deeper aquifer.
