Evaluation of Aquifer Recharge Infiltration through Richards equation–based Approach in Non-carbon Confined Aquifers in Central Bohemian, Czech Republic from 1990 to 2020

The influence of climate change on the level and recharge of groundwater has yet to be well understood. In countries with low cumulative rainfall, such as the Czech Republic, groundwater is an essential source of water supply. In the Czech Republic, between 1990 and 2020, 366 million m$^{3}$ of water from aquifers was used for public water supply networks. Although the air temperature in the Czech Republic continues to rise slowly, from 1981 to 2010, an increase of +1.6°C has been identified in all Czech territories, affecting evaporation and infiltration dynamics. On average, 634 mm of precipitation fell in the country (92% of the long-term average for 1981-2010). These conditions aggravate droughts caused by several consecutive years of below-average rainfall, directly affecting water infiltration, groundwater recharge, and groundwater table fluctuations.

This contribution aims to simulate rainwater infiltration according to evapotranspiration heat, simulating the excess water that can infiltrate and cross the unsaturated zone until it reaches the saturated zone. This research is carried out in non-carbon confined aquifers, where infiltration is assumed to be the primary recharge mechanism in the western Central Bohemian region, Czech Republic. The climate data consists of 2-meter total precipitation and temperature data from the ERA5 reanalysis (provided by ECMWF). On an hourly scale, the analysis is run using disaggregated data from the Amalie Lany region (Central Bohemia). Data disaggregation was achieved through ArcMap and Rstudio.

Water infiltration was achieved using DRUtES (Dual Richards Unsaturated Equation Solver). DRUtES is a free software. It uses Richards's and heat transport equations to describe hydrodynamical processes in variable saturated porous media with surface and subsurface evaporation, surface energy balance and root water uptake.  This model was built to represent over ten observation boreholes in a compacted sedimentary layer followed by fractured layers in the Lany Amalie Watershed. Van Genuchten's median porous parameters, anisotropy description, thermal conductivity, and root zone parameters have been used in this model. Over the past period (1990 - 2020), the infiltration shows a mean of 0.05 mm per hour for each soil profile. Infiltration simulation correlates quantitatively with climate time series data from 1990 to 2020. This first approach evaluates climate change's impact in the last 30 years on aquifer recharge from surface heat in the western Central Bohemian region, where precipitation is an essential resource to supply ponds, energy production, aquifer recharge, and drinking water. 

Keywords: Climate change, Infiltration, Aquifer recharge, Precipitation, Temperature, DRUtES.