Groundwater recharge in suburban areas of Hanoi, Vietnam: effect of decreasing surface-water bodies and land-use change

Kuroda, Keisuke; Hayashi, Takeshi; Do, An Thuan; Canh, Vu Duc; Nga, Tran Thi Viet; Funabiki, Ayako; Takizawa, S

Groundwater recharge in suburban areas of Hanoi, Vietnam: effect of decreasing surface-water bodies and land-use change | Recharge des eaux souterraines dans des régions suburbaines de Hanoï, Vietnam: effet de la diminution des niveaux des masses d’eaux de surface et des changements d’occupation du sol Recarga de agua subterránea en zonas suburbanas de Hanoi, Vietnam: efectos de la reducción de cuerpos de agua superficial y del cambio en el uso de la tierra 越南河内郊区地下水补给:逐渐减少的地表水体和土地利用变化造成的影响 Recarga das águas subterrâneas em áreas suburbanas de Hanói, Vietnam: efeito de corpos d’água superficiais decrescentes e mudança no uso da terra Bổ cập nước ngầm tại khu vực ngoại thành Hà Nội, Việt Nam: ảnh hưởng từ việc suy giảm nguồn nước mặt và sự thay đổi sử dụng đất

2017

Over-exploited groundwater is expected to remain the predominant source of domestic water in suburban areas of Hanoi, Vietnam. In order to evaluate the effect on groundwater recharge, of decreasing surface-water bodies and land-use change caused by urbanization, the relevant groundwater systems and recharge pathways must be characterized in detail. To this end, water levels and water quality were monitored for 3 years regarding groundwater and adjacent surface-water bodies, at two typical suburban sites in Hanoi. Stable isotope (δ¹⁸O, δD of water) analysis and hydrochemical analysis showed that the water from both aquifers and aquitards, including the groundwater obtained from both the monitoring wells and the neighboring household tubewells, was largely derived from evaporation-affected surface-water bodies (e.g., ponds, irrigated farmlands) rather than from rivers. The water-level monitoring results suggested distinct local-scale flow systems for both a Holocene unconfined aquifer (HUA) and Pleistocene confined aquifer (PCA). That is, in the case of the HUA, lateral recharge through the aquifer from neighboring ponds and/or irrigated farmlands appeared to be dominant, rather than recharge by vertical rainwater infiltration. In the case of the PCA, recharge by the above-lying HUA, through areas where the aquitard separating the two aquifers was relatively thin or nonexistent, was suggested. As the decrease in the local surface-water bodies will likely reduce the groundwater recharge, maintaining and enhancing this recharge (through preservation of the surface-water bodies) is considered as essential for the sustainable use of groundwater in the area.

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