The Guadalhorce River flows in the South of the Iberian Peninsula and ends in the West of the city of Malaga (Spain). Its peak discharges take place usually after important, high intensity storm events (>50 mm/day), and it reaches flows up to 1,200 m3/s, which cause a relevant rise of the river stage.
Previous researches have verified that a relationship exists between the different hydrological systems taking place here: the Guadalhorce River, the subjacent aquifers, the wetlands and the Mediterranean Sea. To check this phenomenon in detail, a monitoring network composed by data loggers was installed. These devices record, hourly, river and wetlands stage, groundwater table in wells, as well as electrical conductivity and temperature of waters in wetlands and aquifers. Data loggers allowed to record the behavior of systems between 20/11/2016 and 15/12/2016, when several and intense storm events took place, some of them up to 79 mm/day.
Each one of these storms caused an important increase of Guadalhorce River stage (>1 m), in first place, because it is the hydrological system most sensitive to rainfall. Quaternary aquifer (unconfined) also responds after a few hours, but the behavior of the peaks is very similar to the one showed by the Guadalhorce River, excepting in some points, further from the coast line and the river, where levels remain higher after the storms. Pliocene aquifer (confined) groundwater table shows retarded response respecting Quaternary aquifer and Guadalhorce River. Wetlands’ stage has also a very fast rise due to direct precipitation, but a slight increasing slope is appreciable after this. In the last point, evaporation and groundwater output from wetlands are visible with noticeable decreases. In most of the points, noticeable diminutions of the electrical conductivity of waters are visible when these storms take place because of freshwater recharge. Finally, water temperature of all water bodies diminishes due to the contribution of recharge water, colder.
The monitoring of several hydrological systems using continuous recording devices have allowed to discern their response to rainfall, which takes place in different ways. Guadalhorce River is the first water body showing it, followed by the Quaternary aquifer, the wetlands and the Pliocene aquifer, respectively. This suppose a connection between systems where, at least in high water conditions, precipitations recharge all of them but there is also water flow from the Guadalhorce River towards the Quaternary aquifer and, finally, to the wetlands, with a slight buffer effect. Pliocene aquifer looks to function other way because of its confinement. Different magnitude in variation of groundwater table, electrical conductivity and temperature in the Quaternary aquifer proves variable hydraulic conductivities in this aquifer, which look to be higher in the zone closer to the north arm of the Guadalhorce River splitting.