Catchment Erosion and Sediment Delivery in a Limno-Reservoir Basin Using a Simple Methodology

Accelerated soil erosion is a threat for the societies due to the loss of ecosystems services. Soil erosion and sediment delivery have been assessed in a small catchment of Central Spain with a new water body, the Pareja Limno‐reservoir, located in its outlet. This limno‐reservoir was created in 2006 with environmental and recreational purposes in the riverine zone of a large reservoir. Sedimentation risk is an issue of concern regarding limno‐reservoirs environmental feasibility. Thus, the study of the soil erosion in the Pareja Limno‐reservoir catchment and its sediment delivery seemed of the utmost importance. In this paper we establish an affordable and simple methodology to address it. A soil erosion and deposition monitoring network was installed in the Ompólveda River basin (≈88 km²), which flows into the Pareja Limno‐reservoir. Results obtained were related with those from a sedimentation study previously carried out in the limno‐reservoir. Gross hillslope erosion in the catchment was 6.0 Mg ha⁻¹ year⁻¹, which is in agreement with values reported for Mediterranean areas. After subtraction of the deposition measured, a soil loss of 1.2 Mg ha⁻¹ year⁻¹ was found in the catchment. Sediment delivery ratio (SDR) was estimated to be 3.8 %. SDR is low as a result of the low connectivity between the stream network and the limno‐reservoir. Some local characteristics may also have a secondary influence in the low SDR value. Results obtained support the environmental feasibility of the Pareja Limno‐reservoir from the sedimentation risk perspective. They also demonstrate that the methodology followed allows the assessment of soil loss and sediment delivery at a catchment scale, and the identification of areas where the erosion problems are most severe.