Sediment load variability in response to climate and land use changes in a Carpathian catchment (Raba River, Poland)

Abstract

Purpose: This study analyzes the variability of sediment loads under variant climate change and land use scenarios in a Carpathian catchment with a dam reservoir. The areas with the highest share of sediment loads are tracked to establish possible indications for future catchment management plans. Materials and methods: Analyses were performed for the Raba River catchment (Poland, Carpathian Mountains) with use of the Macromodel DNS/SWAT. The RCP 4.5 climate forecast predictions (2021–2050 and 2071–2100), downscaled for the area of Poland, and land use predictions from the DYNA-Clue model for the Carpathian area, were taken into consideration. A total of seven scenarios were created, accounting for precipitation (P1 and P2), temperature (T1 and T2), land use (LU) changes, and combined effects (COMB1 and COMB2). Results and discussion: The average load delivered to the dam reservoir was estimated as 2.43 Gg y−1, and its seasonal/yearly variability was followed by local meteorological phenomena. Among the tested factors, precipitation change, in terms of total amount and intensity, exerted the most impact on sediment loads causing their increase. Temperature and land use changes resulted in a slight decrease. Combined scenarios implied that changes of the catchment area use, such as increase of forest cover, can noticeably reduce sediment loads delivered into a dam reservoir. Conclusions: The performed simulations revealed the importance of incorporating variant scenarios for catchment management plans, development of land use mitigation measures (erosion), and operational procedures for the dam reservoir. Particular attention should be paid to warmer winters with heavy rainfalls and temperatures above zero, which together with a lack of plant vegetation result in elevated annual sediment loads reaching the dam reservoir. Further changes must be mitigated by anti-erosion investments.