Abstract
In recent years, the potential impacts of climate change on water resources and the hydrologic cycle have gained importance especially for snow-dominated mountainous basins. Within this scope, the Euphrates-Tigris Basin, a snow-fed transboundary river with several large dams, was selected to investigate the effects of changing climate on seasonal snow and runoff. In this study, two headwater basins of the Euphrates River, ranging in elevation between 1500–3500 m, were assigned and SWAT was employed as a hydrological modeling tool. Model calibration and validation were conducted in a stepwise manner for snow and runoff consecutively. For the snow routine, model parameters were adjusted using MODIS daily snow-covered area, achieving hit rates of more than 95% between MODIS and SWAT. Other model parameters were calibrated successively and later validated according to daily runoff, reaching a Nash-Sutcliffe efficiency of 0.64–0.82 in both basins. After the modeling stage, the focus was drawn to the impacts of climate change under two different climate scenarios (RCP4.5 and RCP8.5) in two 30-year projection periods (2041–2070 and 2071–2099). From the results, it is estimated that on average snow water equivalent decreases in the order of 30–39% and snow-covered days shorten by 37–43 days for the two basins until 2099. In terms of runoff, a slight reduction of at most 5% on average volume is projected but more notably, runoff center-time is expected to shift 1–2 weeks earlier by the end of the century.
Highlights
Mountainous regions serve as a lifeline in socio-hydrological systems, as the origin of most rivers stems from such elevations [1,2,3,4]
Since the study comprises high elevated areas, snow is the most significant element of the hydrological cycle. It is well-known that hydrological modeling in snow-dominated basins is challenging due to the scarcity of observed data, considering complex topography and harsh climatic conditions
Over 95% hit rate was achieved comparing MODerate Resolution Imaging Spectroradiometer (MODIS) daily cloud-free snow cover images with Soil and Water Assessment Tool (SWAT) snow outputs for the modeling period
Summary
Mountainous regions serve as a lifeline in socio-hydrological systems, as the origin of most rivers stems from such elevations [1,2,3,4]. Hydrologic modelling in mountainous areas is challenging; [25] reported that SWAT had inadequate performance on high-elevated catchments until a new algorithm was adopted by [26], incorporating elevation bands that discretize the snowmelt process based on basin topographic controls Along with this development, different studies have been applied at various parts of the world on the purpose of observing orographic effects using snow-melt parameters [27,28,29,30]. The novel contribution and main objectives of the current research are: (i) the application of SWAT in snow-dominated mountainous basins as a pioneer study in Turkey, (ii) utilizing remote sensing and ground snow data for model calibration and validation besides runoff, and (iii) evaluating the impacts of climate change scenarios on the mountainous headwater basins. HHHyyydddrrrooo---mmmeeettteeeooorrrooolllooogggiiicccaaalll cccooonnndddiiitttiiiooonnnsss ooofff (((aaa))) MMMuuurrraaattt aaannnddd (((bbb))) KKKaaarrraaasssuuu bbbaaasssiiinnn
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