SEDIMENTARY CHARACTERISTICS OF SAND DUNES IN CAU NGANG AND TRA CU DISTRICTS, TRA VINH PROVINCE AND THEIR FRESHWATER - BEARING CAPACITY

Abstract

Sedimentary characteristics of sand dunes and related deposits in Cau Ngang and Tra Cu Districts, Tra Vinh province are clarified to confirm freshwater-bearing capacity. In the study area, 05 OSL ages of sand dunes are dated from 1620 ± 90 years before present (BP); 1590 ± 90; 1100 ± 60; 970 ± 50 and 770 ± 40 showing the sand dune system of this area had been evolved in progradation of Mekong river delta in late Holocene. Distribution features of aquifer in sand dune in Cau Ngang and Tra Cu are identified on the base of sedimentary structures of sand dunes and surrounding deposits. Aquifer in sand dune with lenticular forms is recharged naturally by rainy water so the water volumn is changed upon the season. The change of water level is appoximately of 1.8 -2.6 during dry and wet seasons. Freshwater-bearing in sand dune is Bicarbonate-clorur-natrium. In the wet season, rainy water is natural recharge source; in the dry season, fresh water from canal or small river would be good artificial recharge source to increase groundwater reserves.