GroMoPo Metadata for Mekong Delta SEAWAT model

Groundwater salinization is one of the most severe environmental problems in coastal aquifers worldwide, causing exceeding salinity in groundwater supply systems for many purposes. High salinity concentration in groundwater can be detected several kilometers inland and may result in an increased risk for coastal water supply systems and human health problems. This study investigates the impacts of groundwater pumping practices and regional groundwater flow dynamics on groundwater flow and salinity intrusion in the coastal aquifers of the Vietnamese Mekong Delta using the SEAWAT model-a variable-density groundwater flow and solute transport model. The model was constructed in three dimensions (3D) and accounted for multi-aquifers, variation of groundwater levels in neighboring areas, pumping, and paleo-salinity. Model calibration was carried for 13 years (2000 to 2012), and validation was conducted for 4 years (2013 to 2016). The best-calibrated model was used to develop prediction models for the next 14 years (2017 to 2030). Six future scenarios were introduced based on pumping rates and regional groundwater levels. Modeling results revealed that groundwater pumping activities and variation of regional groundwater flow systems strongly influence groundwater level depletion and saline movement from upper layers to lower layers. High salinity (>2.0 g/L) was expected to expand downward up to 150 m in depth and 2000 m toward surrounding areas in the next 14 years under increasing groundwater pumping capacity. A slight recovery in water level was also observed with decreasing groundwater exploitation. The reduction in the pumping rate from both local and regional scales will be necessary to recover groundwater levels and protect fresh aquifers from expanding paleo-saline in groundwater.

地下水盐渍化是全球滨海含水层中最为严峻的环境问题之一，会导致多用途地下水供水系统的盐度超标。地下水中的高盐度可在距海岸数公里的内陆区域被监测到，进而提升滨海供水系统的运行风险，并引发诸多人体健康问题。本研究借助SEAWAT模型（SEAWAT）——一种变密度地下水流与溶质运移模型，探究了越南湄公河三角洲滨海含水层中，地下水开采活动与区域地下水流动力学对地下水流场及盐水入侵的影响。该模型采用三维（3D）架构，涵盖多层含水层、周边区域地下水位变化、开采活动及古盐度等要素。模型率定工作为期13年（2000年至2012年），验证周期为4年（2013年至2016年）。选取最优率定后的模型，构建了未来14年（2017年至2030年）的预测模型。研究基于开采速率与区域地下水位设置了六种未来情景。模拟结果表明，地下水开采活动与区域地下水流系统的变化，对地下水位下降及盐分从上层含水层向深层运移具有显著影响。在地下水开采强度提升的情景下，未来14年内，高盐度（>2.0 g/L）水体将向下扩展至150米深度，并向周边区域扩散2000米。而随着地下水开采量减少，地下水位将出现小幅回升。若要恢复地下水位并保护淡水含水层免受古盐渍化扩散的影响，需从局域与区域两个尺度降低开采速率。