Heat transport and temperature distribution during managed artificial recharge with surface ponds

Managed Aquifer Recharge (MAR) is a well-established practice for managing groundwater reserves in a sustainable way. In this paper, we look at the influence of temperature variations of the infiltration water in the recharged aquifer. The paper focuses on MAR systems consisting of an infiltration pond surrounded by extraction wells. A number of different 2D configurations and an operational system in the Belgian dune area are investigated using field observations and numerical modelling with SEAWAT. Seasonally varying temperature in the infiltration water results in a zonation of subsequent lower and higher temperatures in the aquifer. The impact of infiltration water temperature in the aquifer is significant but restricted to the area between the pond and extraction wells, quickly decreasing farther from the infiltration area. Colder water during winter results in a decrease of infiltration capacity which can be as high as 1.5–2 times with respect to summer infiltration. Infiltration water temperature variations equally influence residence times of the infiltrated water. In general, residence times become smaller for water infiltrated during summer and larger for water infiltrated during winter. Infiltration and extraction rate, their ratios and seasonal variability, and location of extraction wells are all contributing factors to the impact of varying temperature of the infiltration water. Finally, it is shown that temperature provides only a rough proxy for residence times of solutes because of the important conduction of heat.