Combination of Tank Model and 3-D Unconfined Groundwater Flow (GWF) Simulation in Tropical Floodplain, THAILAND

Abstract

Thailand is located in a tropical, monsoonal area and is one of the world's top five rice producing countries. However, Thailand's paddy fields in floodplains often have flood problems, and those that require extraction of groundwater for cultivation face problems of the fall of groundwater levels due to over-pumping. The modeling of the 3-D unconfined aquifer groundwater flow (GWF) in tropical floodplains with quaternary sediments such as Phichit floodplain in Thailand is rather complex for several factors concerning the input data. Complicated recharges are caused by floods, river water, rainwater, water held in rice fields, agriculture ponds, and commercial sandpits. This paper presents an estimated recharge rate by the Thiessen polygon tank model with the use of field observation data and the application of the Visual MODFLOW program for the 3-D unconfined aquifer groundwater flow simulation. The simulated groundwater level appears to be in accordance with the observed values with the exception of a few certain locations. In addition, the simulation results indicate that in tropical floodplains, floodwater recharge is the main income of unconfined groundwater.