HORIZONTAL CIRCULAR PUMPING WELLS TO MINIMIZE SALINE WATER UPCONING: WATER RESOURCE DEVELOPMENT MEASURE FOR TROPICAL SAVANNA CLIMATIC NINH THUAN AREA, VIETNAM

Abstract

The relevance. The Southern central region of Vietnam, including Ninh Thuan province, has a tropical savanna climate and has been heavily suffering from drought and water salinization. Ninh Thuan province has faced severe droughts in recent years because of the increase of the frequency and intensity of extreme weather conditions, the water scarcity, and the salinity of the groundwater. The distribution of fresh and saline groundwater in Ninh Thuan plain has three zones: 1) zone of entire profile with fresh groundwater; 2) zone of the upper profile's with fresh groundwater and of the lower profile's with saline groundwater, and 3) zone of entire profile with saline groundwater. The groundwater abstraction facilities in the first zone are vulnerable to salinization from surrounding saline water, while in the second zone are vulnerable to the upconing saline water from below. The aim: to determine the optimal groundwater pumping in respect to given water level drawdown, to show that the horizontal circular wells are the best for minimization of saline water upconing, to determine the relationship between the saline water upconing height and the radii of the horizontal circular wells. Objects: tropical savanna climate, coastal plain, fresh and saline groundwater, aquifer with fresh water in the upper profile and saline water in the lower profile, circular groundwater wells, saline water upconing. Methods: finite element method, dynamic programming, Dagan–Bear model of saline water upconing, superimposition principle in dealing with multiple pumping points for identification of overall saline water upconing. Results. Different schemes of pumping fields with either vertical wells or horizontal circular wells with different radii were analyzed for saline water upconing. The time of saline upconing height in all the alternative schemes were determined. A very well regression curve of the relationship between the time saline water upconing to the horizontal circular wells and the circular well radii was obtained. The analysis results are extremely useful supporting well design in terms of minimization of saline water upconing.

Keywords

• tropical savannah climate
• saline water upconing
• dynamic programming
• finite element
• horizontal circular well