Effect of Population Dynamics and Land Use on the Contribution of Sediments to Reservoirs for Hydropower Generation. Case Study San Carlos River Basin, Colombia

Sediment load in reservoirs results in loss of reservoir storage and reduces its usable life. There are management strategies focused in sediment removal or reducing trapping in reservoirs, and there are basin management strategies oriented to reduce sediment production and load reaching reservoirs. In a social and political moment, like the present time in Colombia, rural return migration is expected. Ex-ante evaluation of strategies to reducing sediment production is required, in order to implement them previously and avoid the acceleration of the reduction of the usable life of reservoirs. One way to evaluate these kind of strategies is to incorporate distributed hydrological models that allow to quantify basin sediment production in a long term and to evaluate effectiveness of these strategies.

This paper presents assessment of the impact on sediment production in a basin according to different land use planning strategies, in the context of the rural population dynamics expected in the coming years in Colombia. The San Carlos River basin contributes to a reservoir for hydropower generation, which currently generates the major percentage of hydropower energy in the power generation matrix of Colombia. We implemented on the basin the TETIS-SED model, a distributed conceptual hydrological and sediment model. This model allows to estimate sediment production, through simulation of solid discharge series at anywhere in the basin. The TETIS sedimentological sub-model was calibrated and validated using reservoir sedimentation volumes as an estimator of the total sediment transport. Reservoir sedimentation volumes were estimated using available data of past and currently bathymetries. Different strategies and alternatives for land use were established, including lack of planning and agricultural policies. Results show an increase in the sediment production in the long term, if no policy on the adequate use of the soil is implemented. The results allow to define the strategic zones of the basin where the efforts for the implementation of good agricultural practices, reforestation and soil conservation must be focused.