Current and future impacts of climate change on river runoff in the Central Asian river basins

Abstract

We investigated the impact of climate change in the Aral Sea basin (Cen-tral Asia) using long term observational time series of three indicators -air temperature, precipitation, and change in river discharge. For each indica-tor data of approximately 200 measurement locations (hydrological and meteorological stations) were considered. Changes and trends in the data were identified using statistical methods and modeling. Missing data in in-dividual time series were estimated using correlations between related sta-tions. The results show that the annual air temperature in Central Asia started to increase considerably after 1950. The time series of mean annual tem-peratures show trends of increasing temperatures of varying magnitude. At some stations temperature trends are affected by human activities, espe-cially in the vicinity of larger cities. On the contrary, no trends in precipita-tion or an increase in the amount of precipitation could be detected in the Central Asian region. No relation between precipitation and temperature increase could be detected. Increasing temperatures accelerate the degradation of glacier fields in the Pamir and Tian Shan mountains which are a major source of river run-324 A.G. Savitskiy, M. Schlüter, R. Taryannikova, N. Agaltseva, V. Chub off in Central Asia. The reduction in glacier area and changes in precipita-tion patterns will alter the flow regime of the rivers – a fact that has been stated before. In this article we present an assessment of the magnitude of the expected changes based on available climate related data and provide examples of the implications of climate change on the flow regime of the river. Analysis of river runoff time series revealed that total runoff has so far changed only little. However, the shape of the hydrograph has changed, which will have strong impacts on the main water users, especially irri-gated agriculture. Given the observed and expected impact of climate change in the Aral Sea Basin and the large uncertainties of predicting future river runoff the paper concludes that new water management approaches are needed that can cope with increasing variability and uncertainty in water availability and their consequences for current and future water users.