GROUNDWATER AND RIVER INTERACTION PARAMETER ESTIMATION ALONG SAIGON RIVER, VIET NAM

Abstract

The Saigon River Basin is one of the largest water resources contributing water supply for domestic and industrial fields at Ho Chi Minh City and Binh Duong Province, and has been facing the drought issue at downstream in recent years. To manage the water resources in Saigon Basin effectively, the groundwater and river interaction parameters need to be assessed systematically In this study, a groundwater modeling of the main stream of Saigon River and river cross-section investigations were applied to analyze groundwater and river interaction parameter along the river. The interaction parameter (KiM-1) was defined as hydraulic conductivity divide by thickness of interaction layer which is a combined layer by materials of riverbed with materials of aquitard or aquifer. The values of conductance through groundwater model calibration by peizometric heads during 2000 to 2007 at three cross-sections in Saigon River were used to estimate the interaction parameter (KiM-1) at correlative cross-section. A function of interaction parameter with percentage of interaction layer width under aquifer was developed to estimate interaction parameter at another cross-section along Saigon River. The results showed the effect of river cross-section morphology on interaction parameter. When river cross-section has no penetration with aquifer, the materials of interaction layer consists of materials of riverbed and aquitard with value of interactions is equal to 0.0003 d-1. In the other hand, the value will be reached to 0.033 d-1 when river cross-section has fully penetration with aquifer. In the upper part of Saigon River, river gained water from groundwater inflow through riverbed (river recharge out) and lost water to groundwater (river recharge in) by out flow through the riverbed in lower part during 2000 to 2007. In the whole study area, river recharge volume increased 26,129 m3/d from 2000 to 2007, and occupied average 34% of total flow in of water budget of qp2-3 aquifer in the study area, compared with 10.1% of land recharge and 17.7 % of storage in. With the effect of increasing pumping rate, the volume of river recharge in grew up approximately 56% from 2000 to 2007 at TV6 cross-section and about 50 % at TV7 cross-section. Hence, from the study, pumping rate of both qp2-3 and qp1 aquifer exceeded total groundwater recharge so, groundwater in the study area needs to be reduced and better managed.