Sediment Delivery Assessment for a Transboundary Mediterranean Catchment: The Example of Nestos River Catchment

Abstract

Nestos River flows through Bulgaria and Greece and discharges into the North Aegean Sea. Its total catchment area is around 6,200 km 2 , while the mean annual precipitation and runoff are 680 mm and 40 m 3 /s, respectively. The Hellenic part of the catchment has undergone a substantial hydroelectric development, since two dams associated with major hydropower pumped-storage facilities are in operation. The main objective of the paper is to assess the expected sediment delivery of Nestos R. at the uppermost Thisavros reservoir site. This has been carried out by implementing the Universal Soil Loss Equation in a GIS environment for determining the mean annual soil erosion in conjunction with a suspended sediment measurement program (114 measurements in total) accomplished between 1965 and 1983 adjacent to the dam site. The sediment discharge rating curve between sediment and river discharges in a power form has been constructed using five alternative techniques, namely (a) the linear regression of the log-transformed variables, (b) the same as (a) but with the Ferguson correction, (c) different ratings for the dry and wet seasons of the year, (d) the nonlinear regression, and (e) the broken line interpolation that utilizes different rating parameters for two discharge classes. It is shown that the mean annual sediment yield is almost equal for all rating curve formulations and varies between 178.5 tkm −2 and 203.4 tkm −2 and the highest value results from the broken line interpolation method. Accordingly, the sediment delivery ratios vary slightly between 17% and 19% of the upstream soil erosion.

Taking advantage of a new hydraulic infrastructure to study the sediment yield in a small basin of central Spain

“…The first one, by Arévalo (2008), uses USLE and RUSLE models Smith 1965, 1978), which are among the most popular methodologies to study soil erosion (e.g. Brath et al, 2002;Zarris et al, 2011). Applying the RUSLE equation and a modification of the USLE model, Arévalo found an average soil erosion between 9.4 and 10.6 Mg ha -1 year -1…”

“…In the Entrepeñas Reservoir -whose maximum water level area includes the Pareja Limno-reservoir-, sedimentation studies revealed that it is filled up at a rate of 0.5% per year (Palau Ybars, 2002). This value can be considered low, since for many reservoirs worldwide annual storage capacity loss can go up to 5% (de Vente et al, 2005;Zarris et al, 2011).…”

Addressing uncertainties in the environmental sustainability of limno‐reservoirs: insights from the synthesis of multidisciplinary research

“…), which is low compared to those reported for many reservoirs elsewhere (around 4%–5%, and even above 6% in some Mediterranean basins; Palau Ybars ; Zarris et al . ). The low sedimentation rate is related to the low sediment delivery ratio (2.2%–3.8%) observed in the Ompólveda River basin (Fig.…”

“…The annual storage capacity of many reservoirs may decrease by up to 4 or 5%, and the entire storage capacity may be lost after only 25–30 years (Zarris et al . ). Spain is one of the countries most severely affected by soil erosion (Solé Benet ), with signs of high soil loss being observed in the catchment of the Pareja Limno‐reservoir.…”

Towards improving the applicability of the RUSLE model at mountainous Mediterranean catchments

“…Due to the lack of detailed precipitation values the Rainfall Erosivity Factor (R) was estimated using the empirical Van der Knijff et al, (2000) equation. The choice was based on a literature review (Sigalos et al, 2010;Zarris et al, 2011). Similarly, the lack of soil properties (granulometry, organic matter content etc.)…”