Development of Erosion Protection Zones in the Catchment of the Kalimanci Reservoir, North Macedonia

Abstract

Construction of reservoirs is a priority for ensuring sustainability of water resources. In the Republic of North Macedonia, there are 23 big and over 120 small water reservoirs. On the other hand, erosion and the filling of reservoirs with sediment is one of the main problems in reducing the lifespan of the reservoir. The total annual accumulated sediment in all the reservoirs in the Republic of Macedonia is 3,000,000 m³ (Erosion map of RM, 1993). The selected study area for the current research is the Kalimanci reservoir in the frames of the catchment of the Bregalnica River, North Macedonia. The main method used to estimate the sediment transport on catchment level is the Erosion Potential Method (EPM; Gavrilovic method), and the validity is assessed on the basis of accumulated sediment in the reservoirs. The EPM method only estimates the total transported sediment at one point. To estimate how the sediment is transported, re-transported, and accumulated in the river bed, a hydraulic sediment transport model (HEC RAS) was used. Then the critical sub-catchments from an erosion point of view are delineated. Most of the critical sub-catchments are situated around the Kalimanci reservoir, while the middle of the catchment experiences erosion of medium severity, and the highest parts of the Bregalnica River are the least critical. The largest part of the sediment transported by the Bregalnica River (nearly 75%) is deposited in the valleys. With the aggregation of the previous steps, the erosion zones of the Kalimanci reservoir were identified.