Modeling Groundwater Recharge Under Coniferous, Grain and Wet Grassland Covers Using Profile Soil Moisture Time Series.

Modeling groundwater recharge under coniferous, grain and wet grassland covers using profile soil moisture time series.

Vicente Vásquez, Kirsten Schelde, Anton Thomsen, Bo V. Iversen

Dept. of Agroecology, Aarhus University, DK-8830 Tjele

 

Abstract

 

Quantifying recharge to shallow aquifers via soil deep percolation is needed for sustainable management of water resources. This includes modeled predictions to address the effects of climate and land use change on recharge. The partitioning of the water balance across three vegetation types was investigated with a soil water flow model (Hydrus1D) for the grain crop and wet grassland and a soil vegetation atmosphere transfer model (COUP) for the coniferous tree. During the dry summer of 2009, the conifer experienced a 30 day period with severe soil moisture stress and effectively reduced ET to 0.3 of the potential rate whereas the grain crop and grass sustain ET at potential rate due to a 50 mm irrigation (grain crop) and a 20 cm water table drop (grass). During the growing seasons 2010-2012 characterized by wet summers, canopy interception in the coniferous tree accounted for 30% of precipitation (P) and resulted in higher ET rates than grain or grass. Recharge in the catchment was dominated by fall and winter P where low atmospheric demand of water coincides with high P. During recharge periods, interception in small winter grain crops and grass was negligible and most of P percolated below the root zone. For the conifer, interception evaporation during winter accounted for 10% of P, effectively reducing R. It was found that the conifer reduced groundwater recharge by 100 mm/year compared with the grain crop and grass and that increasing the afforested area in the future may reduce R in spite of the benefits associated with reduced application of pesticides and chemicals in afforested areas.