Lorraine Williamson
A team from the Doñana Biological Station (EBD-CSIC) of the Spanish National Research Council (CSIC) – an agency of the Ministry of Science, Innovation and Universities – has warned of the “critical condition” of the Santa Olalla lagoon in the Doñana Natural Area. The lagoon is “virtually dry after the summer and with only a superficial layer of residual moisture and mud”.
According to the CSIC, this lagoon has completely dried up for two years in a row, in the summers of 2022 and 2023. This has not been observed before since data collection began. The nature reserve is going through difficult years due to drought and overexploitation.
The environmental monitoring team of the ICTS-Doñana, which is in charge of monitoring biodiversity and natural processes in the protected area, has not been able to take representative water samples for analysis for several days, as “only residual moisture and mud remain”.
In addition, recent studies by the EBD-CSIC have shown that 60% of the lagoons that existed in the 1980s have already disappeared.
Observation by camera
In order to observe the situation of the lagoon in real time, ICTS-Doñana has installed a camera on the shore of the lagoon. The lagoon of Dulce, which is located near Santa Olalla and was also considered a permanent lagoon until a few years ago, “dried up completely in the second week of September, a little more than a month later than last year, when the lagoon dried up in early August”. The lagoon of Hondón has retained water all summer.
How the lagoons work
The Santa Olalla lagoon and all the other lagoons in the National Park, which are located near the dunes, are flooded by water from the aquifer, the underground water supply. This means that the flood cycles depend on the level of the groundwater. When it rains, the water seeps into the aquifer, causing the water table to rise and even rise to the surface, flooding the basins of the lagoons. In addition, Santa Olalla also receives water from the dunes.
Measuring the water level
The ICTS-Doñana has special metres spread throughout the nature reserve. This allows us to measure the water level of the aquifer. The metre closest to Matalascañas, at El Corte lane, just 300 metres from the vanished Charco del Toro lagoon and about three kilometres from Santa Olalla, has been showing a very marked decrease for several years.
“About four years ago, in 2020, the height of the water table at this point was about 7.5 metres. In 2024, it will have dropped to a depth of nine metres, something that had never happened before,” reports the CSIC.
Impact on biodiversity
Studies by the EBD-CSIC show that this development has “a major impact” on the fauna and flora of Doñana, in particular on the community of amphibians and aquatic reptiles, which are particularly vulnerable.