Some opinions about the groundwater origin formation of middle – upper Pleistocene aquifer in Ca Mau peninsula

Abstract

In Ca Mau peninsula region, groundwater resource is the main source of water supply for agriculture, industry, domestic uses. In this paper, the authors study groundwater origin in middle - upper pleistocene (qp2-3) aquifer in Ca Mau peninsula and give some opinions about the groundwater origin formation for planning and managing reasonable, safe, and sustainable. There are many studies about groundwater origin in the Mekong delta plains and these studies showed different results. Up till now, there is not a consensus on an exact origin of groundwater in Mekong delta plains, especially in Ca Mau peninsula. Therefore, the authors use the Xulin approach to determine groundwater origin based on the concentration of ions Na+, Cl-, SO42-, Mg2+. Then we use Piper diagram, Gibbs plot, Mercado plot, and hydro-geochemical section plot to explain the origin of groundwater in Ca Mau peninsula region. The results show that there are 4 types of groundwater origin in the studied region: magnesium – chloride, marine origin; calcium – chloride, deep metamorphic environment; sodium – sulfate, the continental leaching origin; bicacbonnat-sodium, continental environment. The groundwater origins relate to the marine transgression and regression process, or weathering, leaching, and freshwash processes. The groundwater origin formation do not have participation of rainfall water and river water, which are two important components contribute to the groundwater recharge formation. Therefore, researching groundwater recharge of th e qp2-3 aquifer in the Ca Mau peninsula is according to other aspects.

Research of fresh/salt water in Upper-middle Pleistocene (qp\(_{2–3}\)) in Bac Lieu Province

“…Bac Lieu Province has surface water sources affected by tidal regimes, so the area is frequently salinized and polluted [1][2][3]. The soil salinity tendency in coastal aquifers becomes more severe due to the lack of surface water and increased groundwater demand (especially for agriculture).…”

“…Thus, deep groundwater is more reliable and becomes the main water supply for activities in the Bac Lieu Province [4]. However, the document and data for the quality and quantity of deep aquifers: Upper-middle Pleistocene aquifer (qp 2-3 ), lower Pleistocene (qp 1 ), Neogene (n 2 2 and n 2…”

“…) in the study area are still limited. Under the pressure of socio-economic development, population growth, and urbanization, water resources suffer from heavy exploitation as the annual extraction flows are more significant than the recharge in most aquifers, resulting in groundwater levels falling year by year [2,4].…”