Sustainable management of groundwater resources requires detailed knowledge on the amount of recharge. Soil moisture is the relevant storage that controls the movement of water in the unsaturated zone. The scales relevant for groundwater resources are much larger than the scales covered by conventional in-situ soil moisture measurement techniques. Cosmic-ray neutron sensing (CRNS) measures intermediate scale soil moisture with a support volume of tens of hectares and tens of centimeters and thus can contribute to groundwater recharge estimates on the field and small catchment scale. In this context, also the snow water equivalent and its contribution to groundwater recharge can be measured by CRNS.
The aim of this project is to develop a stand-alone method to estimate groundwater recharge from CRNS soil moisture and snow on field scale and above. It will be explored, how this root zone soil moisture can be related to downward fluxes of water also below the vertical footprint of the probe.
For this, dedicated field experiments are conducted for snow and soil water content measurements. As CRNS covers the upper part of the root zone, it will be extended by soil hydrological modelling. The data will be complemented by data from partners of the COSMIC SENSE team. Finally, a numerical model of groundwater levels and horizontal flow to surface water will be set up and tested based on the measurements obtained.