Estimating karst groundwater recharge from soil moisture observations – a new method tested at the Swabian Alb, southwest Germany

[摘要] Understanding groundwater recharge processes is important for sustainable water resource management. Experimental approaches to study recharge inkarst areas often focus on analysing the aquifer response using a disintegration of its outlet signals, but only a few approaches directly investigate therecharge processes that occur at the surface of the system. Soil moisture measurements have a high potential to investigate water infiltration todeeper soil depth or epikarst with an easy and not too intrusive installation. They can yield long-term measurements with high temporalresolution. Using these advantages, we developed and tested a method to estimate recharge based on soil moisture measurements. The method consistsof the extraction of linked events in rainfall, soil moisture, and discharge time series, as well as a subsequent fitting of the parameters of a simpledrainage model to calculate karst recharge from soil moisture metrics of individual events. The fitted parameters could be interpreted in physicallymeaningful terms and were related to the properties of the karstic system. The model was tested and validated in a karst catchment located insouthwest Germany with hourly precipitation, soil moisture, and discharge data of 8 years duration. The soil moisture measurements weredistributed among grassland ( n   =  8) and woodland areas ( n   =  7) at 20  cm depth. A threshold of about 35 % ( ±  8 %) ofvolumetric water content was necessary to initiate effective infiltration. Soil moisture averaged during the wetting period of each event was thebest metric for the prediction of recharge. The model performed reasonably well, estimating recharge during single rainfall events. It was alsocapable of simulating 88 % of the average annual recharge volume despite considerable differences in the performance between years. Theevent-based approach is potentially applicable to other karstic systems where soil moisture and precipitation measurements are available to predictkarst groundwater recharge.

[学科分类] 妇产科学