Abstract ID: 3.12725 | Accepted as Talk | Requested as: Talk | TBA | TBA

High mountain rivers and associated aquatic ecosystems in semi-arid areas are highly susceptible to climate change. Groundwater may play a key role in buffering the impacts by regulating surface water temperature.

In this work, we present and analyze streamflow, water temperature, and air temperature data collected at four altitudes during four water years (2020 -2024) in the Alhorí River (Jerez del Marquesado, Granada, Spain). Additionally, pressure and temperature sensors were installed at different depths (20,0 and -15 cm) in three control sections for thermal modeling with VFLUX V2 (Vertical Fluid Heat Transport Solver), complemented by spring temperature data obtained during field campaigns in 2020.

The river watershed is covered in its entirety by schists receiving 550-600 mm of annual precipitation on average. The Alhorí River originates from a spring at the foot of a moraine (section 1, 2665 m a.s.l.). It flows first through a sparsely vegetated area mixed with small wetlands (section 2, 2048 m ASL) characterized by periglacial weathered sediments. At 2000 m ASL it enters pine forest (section 3, 1790 m ASL) until reaching a gauging station (section 4, 1516 m ASL) under operation since 2000.

The obtained data shows continuous stream flow gains between all sections, especially between sections 1 and 3. The inter-annual variation in stream temperature is decreasing with altitude (section 1: 3.98± 0.29 ºC; section 4:8.84 ± 4.50 ºC) and is lower than that of air temperature (section 1: 6.58 ± 7.80 ºC; section 4:11.37 ± 5.71 ºC). The thermal model indicates groundwater influx to different degrees at all controlled sections.

All these findings underline the importance of groundwater in maintaining river temperatures at a safe level for local aquatic species. It also stresses the usefulness of long-term temperature datasets for understanding groundwater-surface water interactions in high mountain environments.