Climatic Evaluation of Spatiotemporal Trends in Suspended Sediment Flux in the Upper Euphrates River Basin, Eastern Anatolia

Abstract:

In recent years, some changes have been experienced in the climate in the region related to the dam constructions and lake formations within the scope of the Southeastern Anatolia Project (GAP). In the study, we presented a comprehensive analysis of the spatiotemporal trends in suspended sediment flux based on daily gauge measurements of river discharge (Q) and suspended sediment concentrations (SSC) from seven sites along Euphrates River for 30 years in average. In conjunction with satellite data depicting rainfall we infer climatic evaluation of peak SSC events.All the data were obtained through time in order to provide to make the link to sediment removal and erosion - especially in the aftermath of agricultural development and dam construction. Moreover, we combine these data with remotely sensed rainfall to elucidate driving mechanisms for peak SSC (≥99^th percentile) days and assess their impact on the suspended sediment budget. Preliminary results from the gauge data indicate positive correlations between daily river discharge and daily SSC for all stations , i.e. the higher the river discharge, the higher the sediment concentration. This correlation suggests increasing mobilization of transiently stored sediment along the river as the river discharge increases. However, some days are characterized by extraordinary high SSC values that occasionally range 1–2 orders of magnitude above the seasonal average and therefore exhibit large residuals from the fitted Q-SSC relationship. Our preliminary results indicate that in all stations of the study area, the 90^th SSC percentile accounts for more than 55% of the total suspended sediment flux and similarly, the 90^th discharge percentile accounts for maximum 50% of the total discharge flux. Besides, we defined rainstorms as days during which rainfall exceeds the 99^th percentile of all days with rainfall ≥.1 mm/day during the last 15-yr rainfall data set and within each station. We also defined peak SSC days as days in which the SSC exceeds the 99^th percentile of the entire SSC data set from each station. In other words, peak SSC days correspond to the uppermost 1% magnitude of the SSC data set. In case of several successive peak SSC days, we assume a single trigger mechanism and refer to peak SSC events.