Climate change impacts on snow water availability in the Euphrates-Tigris basin

M Özdoğan

doi:10.5194/hess-15-2789-2011

Abstract

Abstract. This study investigates the effects of projected climate change on snow water availability in the Euphrates-Tigris basin using the Variable Infiltration Capacity (VIC) macro scale hydrologic model and a set of regional climate-change outputs from 13 global circulation models (GCMs) forced with two greenhouse gas emission scenarios for two time periods in the 21st century (2050 and 2090). The hydrologic model produces a reasonable simulation of seasonal and spatial variation in snow cover and associated snow water equivalent (SWE) in the mountainous areas of the basin, although its performance is poorer at marginal snow cover sites. While there is great variation across GCM outputs influencing snow water availability, the majority of models and scenarios suggest a significant decline (between 10 and 60 percent) in available snow water, particularly under the high-impact A2 climate change scenario and later in the 21st century. The changes in SWE are more stable when multi-model ensemble GCM outputs are used to minimize inter-model variability, suggesting a consistent and significant decrease in snow-covered areas and associated water availability in the headwaters of the Euphrates-Tigris basin. Detailed analysis of future climatic conditions point to the combined effects of reduced precipitation and increased temperatures as primary drivers of reduced snowpack. Results also indicate a more rapid decline in snow cover in the lower elevation zones than the higher areas in a changing climate but these findings also contain a larger uncertainty. The simulated changes in snow water availability have important implications for the future of water resources and associated hydropower generation and land-use management and planning in a region already ripe for interstate water conflict. While the changes in the frequency and intensity of snow-bearing circulation systems or the interannual variability related to climate were not considered, the simulated changes in snow water availability presented here are likely to be indicative of climate change impacts on the water resources of the Euphrates-Tigris basin.

Highlights

It is widely accepted that projected changes in our climate associated with increasing concentrations of greenhouse gases in the atmosphere will fundamentally alter the magnitude and seasonal variations in temperature and precipitation patterns in many parts of the globe (IPCC, 2007a)
What is less known is the impact this change will have on water resources and freshwater ecosystems, especially in mountainous regions where much of the regional water supply is stored as snowpack and glaciers that melt into rivers (Hamlet and Lettenmaier, 1999; Beniston et al, 2003; Mote et al, 2005)
The temperature change was computed as the absolute difference between the baseline conditions and the climate change scenarios, positive values indicate increases in air temperature

Summary

Introduction

It is widely accepted that projected changes in our climate associated with increasing concentrations of greenhouse gases in the atmosphere will fundamentally alter the magnitude and seasonal variations in temperature and precipitation patterns in many parts of the globe (IPCC, 2007a). What is less known is the impact this change will have on water resources and freshwater ecosystems, especially in mountainous regions where much of the regional water supply is stored as snowpack and glaciers that melt into rivers (Hamlet and Lettenmaier, 1999; Beniston et al, 2003; Mote et al, 2005). In mountainous ecosystems of the world, seasonal snowpack is a key component of the hydrologic cycle, storing water in winter and releasing it in spring and early summer, when hydroelectric, agricultural, ecological, and recreational demands for water are greatest. In many mountainous river basins, snow is the largest component of water storage but the availability of snow makes these basins most vulnerable to climatic variations and changes that influence winter snowpack. Less snow means reduced power output in downstream generators, as well as negative impacts to ecosystem functions, including aquatic habitat, fish migration, and wetland replenishment

Methods

Results

Discussion

Conclusion