Estimation of Groundwater Use Pattern and Distribution in the Coastal Mekong Delta, Vietnam via Socio-Economical Survey and Groundwater Modelling

In many provinces of Mekong delta, excessive groundwater extraction has resulted in many serious groundwater-related problems. To solve problems relevant to increasing water demand as well as other negative influence of groundwater depletion, an exigent question was raised whether at what time in future is the limits to local groundwater use reached? Hence, there is a need to know groundwater use (GWU) pattern and distribution in the study area for future groundwater management. In this study, firstly, the study used socio-economic data of Tra Vinh Province to classify groups of gross domestic product (GDP) per capita, potential of water resources and population distributed in each district in order to design and conduct the socio-economic survey and to explore information relevant to GWU for each purpose. Secondly, the data set of 419 survey questionnaires per 9 surveyed communes were analysed by SPSS tool to estimate ratio of household using groundwater (RHHUG) for each purpose as well as average pumping rate (APR) per household for domestic use and per ha for agriculture use, respectively. Thirdly, the APRs were extended to propose the total GWU pattern and distribution during 2007-2016 by using socioeconomic data of the province and expand to spatial distribution by using correlation with land surface temperature (LST) which was estimated from Landsat 8 images. Besides, the groundwater flow model of the study area was developed to verify the estimated amount of groundwater pumping (pattern and distribution) in the period. The study found that the GWU of Tra Vinh Province in dry season of 2016 was 346,279 m3/d in which two coastal districts occupied more than 50 percentages, i.e., about 188,551 m3/d. RHHUG increased from 1.5 to 2 times during the period of 2007 to 2016 in this area. LST distribution performed a good correlation (adj-R2 = 0.646) with GWU distribution in Tra Cu district. Results of groundwater modelling also showed that the discharge from aquifer (mainly pumping) was always higher than the recharge to aquifer.