Using isotope technique to estimate groundwater recharge in the Red river delta plain

Abstract

   The Red river delta plain is the second largest delta in Vietnam and is located in the North of the country with an area of 14,860 km² and residing more than 22.5 million inhabitants. Groundwater is mainly exploited in Quaternary sedimentary aquifers with a total discharge of about 3 million m3/day. Some localities have shown signs of over-exploitation such as in Hanoi and in Nam Dinh, which may lead to related problems such as depletion, subsidence, saltwater intrusion, and water pollution. In order to be able to sustainably exploit groundwater, the groundwater recharges need to be estimated. There have been many studies referring to different methods of estimating the groundwater recharge in which the most effective one is the isotope technique. Field trip and water sampling for chemical compositions, stable isotopes 18O, 2H, and radioactive 3H analysis were also implemented. Ground recharge rate in the range from 77 to 440 mm/year was estimated by using isotope analysis and interpretation