Flood hazard mitigation using managed aquifer recharge: Numerical assessment of a pilot trial in the Nam Kam River Basin, NE Thailand

Abstract

Flash flooding is one of the most catastrophic natural hazards. These disastrous events may trigger some rainfall-related geohazards, e.g., landslides and slumps. Sakon Nakhon Province, partly located in the Nam Kam River Basin, has been severely damaged by storm-driven floods. Due to the effect of climate change, precipitation has changed in intensity, pattern, and frequency. In 2017, this area was hit by a tropical cyclone causing heavy rainfall and considerable flash flooding. Consequently, residential properties, agricultural areas, and infrastructure facilities were devastated. The storm eventually caused 3-million-dollar worth of damage in the province.

The challenge for policymakers is to develop strategies that can provide long-term solutions to reduce extensive damage caused by the hazards. This study drew on examples of the use of managed aquifer recharge (MAR) as an approach primarily to prevent flood-related issues and store stormwater runoff. The MAR system comprises settling and infiltration ponds constructed in an area of 8,000 m2 . A modeling approach is widely known as a scientific and reliable method for the assessment of MAR systems. Therefore, a groundwater model was developed to simulate MAR and the subsequent movement of groundwater. The MAR model was constructed using a notable 3D groundwater-flow model known as MODFLOW-NWT, in association with a MODPATH particle-tracking model. The model accounted for interactions between artificial lakes (Lak Package) and groundwater. Two model scenarios were developed based on the actual MAR methods applied at the demonstration site: (1) An infiltration pond scenario and (2) an infiltration pond with four recharge wells scenario.

The results revealed that the flow model had an acceptable accuracy with an NRMSE of 8.98%. The annual rate of pond seepage was 90,052 m3 . Additionally, artificially recharged water simulated by virtual particles could travel in the system for at least ten years, with a maximum travel distance of 698.07 meters (0.19 meters/day). In addition to recharge ponds, the runoff was recharged directly into the aquifer via the recharge wells. An annual recharge rate is about 22,600 m3 . The deeper-and-longer flow paths were roughly doubled in the distance compared to the first scenario, being up to 1,683.16 meters away from recharge wells with an average rate of 0.46 meters/day. In conclusion, the MAR system is a practical solution to capture runoff, mitigate downstream flooding, and enhance groundwater storage for sustainable water management. Most importantly, the system may provide indirect solutions for preventing geohazards within the context of river floods, landslides, and slumps.