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.