A 3D-numerical simulation of groundwater flow and salinity in a rice field adjacent to a marine shrimp farm

Abstract

Rice plants are impacted by high soil salinity, which causes dehydration, stunted growth, and eventual death. It is critical to comprehend the groundwater flow behavior and salinity distribution in a rice field. Thailand’s Samut Sakhon Province features territory that borders the ocean where rice and shrimp are grown. Because of this, the goal of the current study is to perform a 3D analysis of the groundwater flow and soil salinity in a rice field next to a shrimp farm. Darcy’s law was used to estimate the flow of groundwater, and a dispersion model was used to examine the salinity of the soil. The governing equations of a three-dimensional domain were solved by running a finite element method in COMSOL Multiphysicsë software. The results and the numerical simulations agreed closely with those from previous studies. Within the marine shrimp farm pressure, flow velocity, and salinity concentration were highest at the topsoil surface, decreasing with depth. Furthermore, the results were higher near the left edge of the shrimp farm, falling when measurements were taken closer to the right border with the rice field. The gradients of both velocity and salinity were maximal at the topsoil surface, reducing towards the lowest depths. Flows from left to right and from bottom to top in the rice field created a semi-circular zone. We also examined salinity concentrations at the topsoil surface and in the region at a depth of not more than 5 meters. This may help selection of cultivars that are suitable for planting in such areas. The salinity concentration here was found to be rather low, with electrical conductivity of between 0 dS/m and 2.08 dS/m, which tends to support results from previous research.