Numerical simulations of evaluating dynamic interactions between groundwater and river water in GWHP operated riverside area

Abstract

<p>The riverside area is suitable for operating the Groundwater Heat Pump (GWHP) system because it has abundant groundwater. In riverside area, inflow of river water can occur due to the hydraulic gradient between the river water and the groundwater. The mixing of the two waters can cause changes of groundwater temperature. Because GWHP systems use a stable temperature of groundwater as the heat source, groundwater temperature changes can affect operational efficiency. Therefore, in order to operate the GWHP system in the riverside region, it is important to understand how the mixing of river water and groundwater affects the groundwater background temperature. In addition, the temperature of groundwater re-injected into the aquifer after heat exchange in the GWHP system can also affect the background groundwater temperature. In this study, 3D groundwater flow and heat transport modeling was conducted based on groundwater and river water level and temperature monitoring data in order to investigate the mixing of river water and groundwater. Solute transport model was used to calculate the mixing ratio of river water and groundwater to determine whether it affects GWHP system. The model was also used to predict the effects of long-term GWHP system operation in the study area for more than 30 years. The model results predicted the sustainability of the GWHP system by understanding changes in groundwater temperature distribution in the study area.</p>