Author(s): Marina Cantalejo; Agustin Millares; Manuel Cobos; Jorge Pedro Galve; Cristina Reyes-Carmona; Asuncion Baquerizo

Linked Author(s): Marina Cantalejo, Agustín Millares, Manuel Cobos, Cristina Reyes-carmona

Keywords: Mountainous basins; Climate change; Snow dynamics; Soil loss; Fluvial processes; Reservoir sedimentation

Abstract: Mountainous semi-arid basins are characterized by the snow cycle influence on water resources, runoff and their effects on soil erosion and fluvial processes. Future climate projections are expected to show drastic changes in meteorological conditions at these areas such as increasing temperature and intensity of precipitation events and longer droughts periods, which would lead to important changes on snow dynamics. This work analyzes the effect of different climatic scenarios on hydro-meteorological drivers and, subsequently, on runoff, erosion and fluvial processes in a semi-arid high mountain basin, the Guadalfeo river basin, southern Spain. Two different climate change scenarios (RCP 4.5 & 8.5) have been considered to evaluate the variability and uncertainty of hydrological and erosive responses by the end of the century. Projections of precipitation, temperature and sun radiation from different global climate models (GCM) have been spatially regionalized to attend to the local statistical behavior of the mountainous environment and to the nonstationary character of climate forcings (Cobos et al. 2021). A distributed and physically-based hydrological model —configured, calibrated and validated in the study area after more than 20 years of monitoring works— was used to reproduce in detail the hydrological processes in this watershed and their effects on erosion by raindrop impact, and rill processes for the different regionalized climatic scenarios. Results show that climate projections produce a noticeable change in the magnitude of runoff (about 30 - 60 %) as well as important time lags. This causes an increase of the peak flow and sediment transport by suspended and bed load. An exacerbation of raindrop impact and rill erosion processes associated with extreme events was also observed (close to 5%), also increased by the lessen of snow coverage (which could reach 85 %). On the other hand, for some GCM a lower amount of soil loss is predicted due to the decrease in the total annual amount of precipitation (between 100-200 mm less than actual annual precipitation values). In the conference, the expected sediment balance and its repercussion on the reservoir siltation downstream will be presented. REFERENCES •Cobos, M., P. Otiñar, P. Magaña & A. Baquerizo (2021). A Method to Characterize Climate, Earth or Environmental Vector Random Processes. Preprint. 10.21203/rs.3.rs-1026259/v1

DOI: https://doi.org/10.3850/IAHR-39WC2521711920221797

Year: 2022