Investigation of Low- and High-Flow Characteristics of Karst Catchments under Climate Change

Abstract

It is not clear how projected climate change will impact the hydrological functioning of complex catchments that have significant karst characteristics. Therefore, in this paper we focused on the investigation of the low- and high-flow characteristics of the karst Ljubljanica River catchment. One smaller (51 km2) and one larger (1135 km2) catchment were selected in order to investigate the projected climate change impact on the hydrological conditions. For the investigation of the hydrological situation in the future, we used a lumped conceptual hydrological model. The model was calibrated using past measured daily data. Using the calibrated model, we investigated the impact of five different climate models outputs for the moderately optimistic scenario (RCP4.5). We investigated the situation in next 30-years periods: 2011–2040, 2041–2070, and 2071–2100. Several low and high-flow indices were calculated and compared. The results indicate that a summer precipitation decrease (i.e., 2011–2070) could lead to lower low-flow values for the investigated areas, which could increase the vulnerability of karst areas. Thus, additional focus should be given to water resource management in karst areas. On the other hand, mean flow could increase in the future. The same also applies for the high-flows where flood frequency analysis results indicate that a climate adaptation factor could be used for the hydrotechnical engineering design. However, differences among investigated models are large and show large variability among investigated cases.

Nossana Spring (Northern Italy) under Climate Change: Projections of Future Discharge Rates and Water Availability

“…The model ensemble returns better results in terms of the maximum number of consecutive days below the thresholds, which are slightly underestimated with the exception of the lower threshold during the calibration period. Specifically, for the calibration period and the 1.32 m 3 s −1 (1.52 m 3 s −1 ) threshold, this index is calculated as 10 (46) days for observations and 58-63 (35)(36)(37)(38)(39)(40)(41)(42)(43)(44) days for the model ensemble. The consecutive number of days below the threshold can therefore be considered the most reliable parameter to evaluate the future behavior of the Nossana Spring and discuss its future management.…”

“…Input-output models can be used to relate the precipitation contribution to the outflow through empirical equations based on lumped parameters (e.g., [30,31]), neural networks (e.g., [32]), or input-response functions (e.g., [33,34]). An increasing number of studies involving such modelling approaches have been documented for karst environments in recent years (e.g., [35][36][37][38][39]). Due to the lack of physical processes representation, a limitation of these models concerns their loss of reliability if applied in conditions that largely differ from calibration [40,41].…”

Assessment of Climate Change Impacts on Extreme High and Low Flows: An Improved Bottom-Up Approach

“…The selection of an adequate stochastic weather generator is crucial to efficiently explore a wide range of climate risk scenarios for water resource systems [21].…”

“…Moreover, Novotny and Stefan [80] found 7-day low flows to be increasing at a significant rate in three major river basins of Minnesota during both the summer and winter. In general, both lowand high-flows have been investigated in various regional studies, with no consistent conclusions in terms of how they will be altered by climate change [21]. Rather, it is believed that such extremes are very localized and dependent on the selected GCMs and hydrological models; thus results cannot be simply generalized.…”

“…By using modelled climate data, precipitation-runoff models are frequently used to simulate hydrological processes, quantify potential impacts of climate change, and identify water availability issues, particularly under extreme conditions. There are two common types of extreme streamflow that are usually considered in impact studies: peak events (causing flooding) using frequency analysis and low streamflow indices (causing drought) [20,21]. Extreme high and low flow indicators based on return periods are used for efficient and safe engineering designs.…”