Groundwater recharge in Mekong River Delta: An application of the water-table fluctuation method in the Long Xuyen Quadrangle and the Ca Mau Peninsula

Local groundwater recharge was determined using the Water Table Fluctuation method in the Long Xuyen Quadrangle and the Ca Mau Peninsula to refine existing estimates in a range of aquifer lithologies in light of climate change. The approach takes advantage of long term monthly water level records of Vietnam by Division of Water Resources Planning and Investigation for the South of Vietnam. An analysis of water levels in eight observation wells during four climatically distinct years (2005, 2009, 2013, and 2020) was used in combination with the monthly meteorological data. Groundwater recharge was estimated by the Water Table Fluctuation method to vary from 95.7 to 150.4 mm/year and account for 5.3 to 7.5% of the total rainfall. The estimates fall within the range of values used in regional-scale recharge models and demonstrate the potential of the Water Table Fluctuation method for resolving spatial and temporal variations of groundwater recharge

Groundwater flow section modelling of salinisation processes in the Champhone Catchment, Savannakhet Province, Lao PDR

A steady state, two-dimensional vertical section groundwater flow model has been developed for a salinised area of the Xe Champhone catchment in Savannakhet province, Southern Lao PDR. The area is underlain by evaporite beds and clastic sedimentary rocks of the Khorat Group that are the source of salt found in groundwater and surface soils. The Xe Champhone catchment is of interest because of plans for construction of several new reservoirs and extensive expansion of irrigated areas. This study provides an example of how a relatively sparse and limited data set has been used to construct and successfully calibrate a numerical flow model to investigate groundwater flow patterns and potential impacts of increased groundwater recharge on land salinisation. Results show the predominance of local flow systems and that deeper flow systems in contact with the rock salt layer operate over much longer time scales in the order of millions of years

Landfill site characterisation at Kham Bon village, Muang district, Khon Kaen province, NE Thailand

The aim of the study is to characterise the Kham Bon landfill site. Hydrogeological and geochemical surveys were conducted and four boreholes were drilled. The hydraulic properties of the aquifer were tested, and soil, surface water and groundwater samples were collected at various times in the year. The physical and chemical properties of the samples, especially heavy metals, were analysed. The results indicated that Cd, Cr, Pb, Cu and Zn occurred in significant concentrations in the soil. The concentrations of Pb, Fe and Mn are high in surface water and groundwater. Moreover, the groundwater chemistry of the shallow aquifer was characterised by high concentrations of some ions. The major factors controlling leachate production and migration in this area are the seasonal variations in precipitation, the site topography, which controls the runoff patterns, and the soil type, which affects infiltration and solute transport to the water table. Copyright © 2009, Inderscience Publishers

Land Use and Hydrological Management: ICHAM, an Integrated Model at a Regional Scale in Northeastern Thailand

Abstract: Soil salinity is a major problem in Northeastern Thailand as a result of the interaction of groundwater flow systems with widespread deposits of rock salt. Successful salinity management would involve changing land use and water balances at a regional scale with a time scale of 30 to 50 years. The scientific issue requires multidisciplinary cooperation including hydrologists, hydrogeologists, agronomists and economic and social researchers. A major issue is the real complexity of the quantitative relationships driving salinity under different environments and the uncertainty resulting from data limitations. This requires that modelling frameworks be open and accessible to a range of disciplines as well as allowing flexibility in coefficient values. This paper reports on interdisciplinary research in progress on salinity and land use in Northeastern Thailand using a combination of bio-economic modelling to assess the socioeconomic impacts of changing land uses, including the use of agroforestry to manage salinity, and groundwater modelling. Models that were derived originally to support the investigation of salinity in the Liverpool Plains of New South Wales, Australia have been redeveloped for application to Northeastern Thailand. The earlier models used the GAMS ™ language but the current modelling is being developed in EXCEL ™ and MODFLOW ™ for ease of use. Preliminary results of the modelling indicate that the saline land area will increase under a “do nothing ” scenario, from the present 13 % of land area to 24 % in 30 years. Th