Abstract
Comprehensive management of karst water resources requires sufficient understanding of their dynamics and karst-specific modeling tools. However, the limited availability of observations of karstic groundwater dynamics has been prohibiting the assessment of karst water resources at regional to global scales. This paper presents the first global effort to integrate experimental approaches and large-scale modeling. Using a global soil-moisture monitoring program and a global database of karst spring discharges, the simulations of a preliminary global karstic-groundwater-recharge model are evaluated. It is shown that soil moisture is a crucial variable that better distinguishes recharge dynamics in different climates and for different land cover types. The newly developed dataset of karst spring discharges provides first insights into the wide variability of discharge volumes and recharge areas of different karst springs around the globe. Comparing the model simulations with the newly collected soil-moisture and spring-discharge observations, indicates that (1) improvements of the recharge model are still necessary to obtain a better representation of different land cover types and snow processes, and (2) there is a need to incorporate groundwater dynamics. Applying and strictly evaluating these improvements in the model will finally provide a tool to identify hot spots of current or future water scarcity in the karst regions around the globe, thus supporting national and international water governance.
Highlights
In many countries, karst groundwater is the dominant or even the only available source of freshwater (Stevanović 2019)
Over 18 months of soil moisture data were recorded at the sites by the global monitoring program and >400 time series of karst spring discharges were collected for the global karst spring hydrograph database (Fig. 4)
The soil moisture is increasing with depth at both vegetation type plots
Summary
Karst groundwater is the dominant or even the only available source of freshwater (Stevanović 2019). Climate models indicate that in the 100 years, karst regions will experience a strong increase of temperature and changes of precipitation in many regions (Hartmann et al 2014). Policies to ensure an optimal level of adaptation and mitigation can only be developed if quantitative and reliable estimates of potential changes to karst water resources are available at the same scales. Even though strong progress in estimating global water stress was made in the previous years (Wada et al 2014; Döll et al 2016; de Graaf et al 2019), most large-scale modeling studies did not consider the particularities of karst hydrogeology and have limited applicability for water resources management (Hartmann 2016)
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