Author(s): Miguel Angel Perez-Martin; Clara Estrela-Segrelles; Carlos Minana-Albanell; Carlos Mulet-Rojas

Linked Author(s): Clara Estrela-Segrelles

Keywords: Climate Change; River Restoration; Water Temperature; Energy model; Reservoirs

Abstract: Climate change is producing an increase in air temperature, 5ºC in the Júcar river head in summer at the end of the 21st century under RCP8.5 scenario, which represents an increase in water temperature, 4 ºC in summer, and then a large number of fluvial ecosystems in Mediterranean rivers will be in risk. The increase in temperature affects to the river macroinvertebrates, the water content of oxygen and, especially, to the cold-water species, such as common trout, which can lose most of their potential habitat disappear in the Mediterranean rivers. Over the next few years, nature-based adaptation strategies for Mediterranean rivers have to be put in place, which compensate for the temperature increases due to climate change. River restoration with the generation of shadows in rivers reduces direct solar radiation on water bodies, so that it can reduce the temperature of river water. The use of a energy balance mathematical model on the river allows to quantify the effect of the degree of vegetation cover on the water temperature in the river. The daily model of energy balance in water developed includes the energy from solar radiation, both direct and diffuse radiation, the heat exchanges of water with the atmosphere, associated with the heat emission from air and water, relative air humidity and wind speed. The model obtains as a result the water temperature, which is compared with the observed data available in different control points of the Júcar river. The model has obtained very good fits both, river stretches and the water stored in reservoirs. Results show that changes in vegetation cover produce significant changes in water temperature, which may be higher than the temperature increase due to the climate change scenarios. An increase of 10% in the degree shadow cover in the river can reduce the temperature of the water by 1ºC. Results obtained in the case of the Júcar River indicate that the increase in vegetation cover can compensate for the temperature increases due to climate change, even being able to recover the habitat of the common trout in some sections where it has now disappeared. Water reservoirs regulation also have a very important role in water temperature in regulated rivers that can significantly affect the ecosystem. The water management of reservoirs including water temperature as a decision variable can produce a very important role in the temperature of the river water and the ecosystem preservation.

DOI: https://doi.org/10.3850/IAHR-39WC2521711920221670

Year: 2022