Attribution of Runoff Decline in the Amu Darya River in Central Asia during 1951–2007

Abstract

Runoff in the Amu Darya River (ADR) in central Asia has been declining steadily since the 1950s. The reasons for this decline are ambiguous, requiring a complete analysis of glaciohydrological processes across the entire data-scarce source region. In this study, grid databases of precipitation from the Asian Precipitation–Highly Resolved Observational Data Integration Toward Evaluation of Water Resources (APHRODITE) and temperature from Princeton’s Global Meteorological Forcing Dataset (PGMFD) are used to force the distributed, glacier-enhanced Soil and Water Assessment Tool (SWAT) model to simulate glaciohydrological processes for 1951–2007 so as to determine long-term streamflow changes and the primary driving factors in the source region of the ADR. The study suggests that the database was a suitable proxy for temperature and precipitation forcing in simulating glaciohydrological processes in the data-scarce alpine catchment region. The estimated annual streamflow of 72.6 km3 in the upper ADR had a decreasing trend for the period from 1951 to 2007. Change in precipitation, rather than in temperature, dominated the decline in streamflow in either the tributaries or mainstream of the ADR. The streamflow decreased by 15.5% because of the decline in precipitation but only increased by 0.2% as a result of the increase in temperature. Thus, warming temperature had much less effect than declining precipitation on streamflow decline in the ADR in central Asia in 1951–2007.