Abstract:
The Plaichumphol Irrigation Project is an irrigation area which depends on both irrigation water and groundwater for long time. Farmers in that area have their cultivation almost whole year. Therefore groundwater supply is a major alternative source especially in dry periods. The aims of this study are to understand the interactions and parameters of land and river recharge, to analyse the surface water and the surface water and groundwater interaction mechanism via development of local groundwater model.
For this purpose, groundwater flow model (GMS) was used to develop regional and local groundwater models. The model was calibrated from 1993-1997 and verified from 1998-2003 using the peizometric heads observed. The results of showed that simulation values were closed with observed data. The proper interaction parameters: land and river were measured in the field using soil moisture sensor and seepage meter to investigate land recharge and estimate river conductance. HYDRUS-1D software package was used to analyse deep percolation rate and seepage meter was modified to measure the flow along the river. The values of these interaction parameters were used to check with the calibrated interaction parameters from the local groundwater model developed.
The interaction volume and patterns between surface water and groundwater were analysed from flow budget via developed local groundwater simulation. Groundwater flow from the upstream boundary area into the aquifer is the main input to the aquifer system with 13.2MCM/day and the downstream boundary outflow is about 4.18MCM/day. The river recharge to the aquifer is the second input and equals to 3.15MCM/day while the river gain is 4.28 MCM/day in average. Land recharge to the aquifer is 0.25MCM/day. The net of the aquifer recharge (river gain) to the river at upstream is 2,385m3/day and river loss to the aquifer at downstream is 1,493m3/day. The main sources of groundwater input are from upstream boundaries and river recharge.
To counter with water shortage in the area in the future, more intensive groundwater management is necessary to keep groundwater level at the appropriate level before the dry season.
