Abstract
Abstract. Karst systems are important for drinking water supply. Future climate projections indicate increasing temperature and a higher frequency of strong weather events. Both will influence the availability and quality of water provided from karst regions. Forest disturbances such as windthrow can disrupt ecosystem cycles and cause pronounced nutrient losses from the ecosystems. In this study, we consider the time period before and after the wind disturbance period (2007/08) to identify impacts on DIN (dissolved inorganic nitrogen) and DOC (dissolved organic carbon) with a process-based flow and solute transport simulation model. When calibrated and validated before the disturbance, the model disregards the forest disturbance and its consequences on DIN and DOC production and leaching. It can therefore be used as a baseline for the undisturbed system and as a tool for the quantification of additional nutrient production. Our results indicate that the forest disturbance by windthrow results in a significant increase of DIN production lasting ∼ 3.7 years and exceeding the pre-disturbance average by 2.7 kg ha−1 a−1 corresponding to an increase of 53 %. There were no significant changes in DOC concentrations. With simulated transit time distributions we show that the impact on DIN travels through the hydrological system within some months. However, a small fraction of the system outflow (< 5 %) exceeds mean transit times of > 1 year.
Highlights
Karst systems contribute around 50 % to Austria’s drinking water supply (COST, 1995)
Forest disturbances pose a threat to water quality through the mobilization of potential pollutants, and these disturbances are likely to increase in the future (Johnson et al, 2010; Seidl et al, 2014)
The semi-distributed simulation model considers the variability in karst system properties by statistical distribution functions spread over Z = 15 model compartments (Fig. 3)
Summary
Karst systems contribute around 50 % to Austria’s drinking water supply (COST, 1995). Karst develops due to the dissolvability of carbonate rock (Ford and Williams, 2007) and it results in strong heterogeneity of subsurface flow and storage characteristics (Bakalowicz, 2005). The resulting complex hydrological behaviour requires adapted field investigation techniques (Goldscheider and Drew, 2007). Forest disturbances (windthrows, insect infestations, droughts) pose a threat to water quality through the mobilization of potential pollutants, and these disturbances are likely to increase in the future (Johnson et al, 2010; Seidl et al, 2014)
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