Doñana practically no longer has a lagoon that conserves water throughout the year. Santa Olalla, the largest of the 3,000 lagoons in this lagoon system declared a World Heritage Site, has certified that it is no longer permanent because it did not survive the summer for the third year in a row. Today its condition is critical, completely dry except for a surface layer of residual moisture and mud, which has a huge impact on the flora and fauna.
After barely enduring the harshest summer months, the prolongation of the drought and the high temperatures with which autumn entered ended up putting the finishing touches. This was certified by the Doñana Biological Station (a research organization attached to the CSIC), which adds another key factor to this combination: the overexploitation of the aquifer. Since records began in the 1970s, Santa Olalla has dried out during extreme droughts, but this has never happened for more than one consecutive year.
The summer, furthermore, was not easy at all, as it hosted a huge overabundance of algae (with a risk of toxicity to fish and birds) due to the high concentrations of nutrients, the heat and the low mobility of water, which decreased its surface area was found to lead to an increase in salinity. As it was, he arrived at the beginning of September very ill, reduced to 5.68 of his more than 47 hectares, or barely 12%. Today, his appearance is little more than a lump of mud, as seen on the camera monitoring his condition.
Santa Olalla started the new hydrological year (October to September) completely dry, although the rains – very welcome but short-lived – allowed the level of the aquifer to rise, allowing it to reach its maximum flood level in February. Its neighbor Laguna Dulce (which until recently was also considered permanent) suffered the same fate and ran out of water earlier, during the second week of September. The only one that survived this year without drying out is that of Hondón.
Lagoons that depend on the aquifer
It must be taken into account that Santa Olalla, like all the Doñana lagoons close to the dune area, depends on the level of the aquifer, which recharges when it rains and in this way – if the water table rises sufficiently – water emerges outside flooding the bucket. But drought and overexploitation of underground resources have already led to the disappearance of 60% of the lagoons that existed in the 1980s, and the survivors are flooded much less and for a short time.
For the Biological Station, this shows that “direct human action interferes with the natural cycle”. According to him, the best evidence is that it mainly affects the water bodies closest to intensively irrigated crops and the large tourist development of Doñana, in the municipality of Almonte.
Many of these lagoons have the basin invaded by terrestrial vegetation, “which indicates a change without return”. Santa Olalla is already on this path, which is now only in tatters and “has already lost a large part of its former extension”, as corroborated by aerial images showing tamarisks and terrestrial vegetation conquering its current banks and its central island. And one more example: four years ago the water table was 7.5 meters and today it has fallen to nine meters, “something that had never been seen until now”.
Great impact on flora and fauna
The combination of an aquifer from which more water is withdrawn than it is recharged and a long decade of drought (this period had a little more rain, but it remains below average) therefore causes the disappearance of the lagoon system. This has a great impact on the park’s flora and fauna, particularly amphibians and aquatic reptiles, which are the most vulnerable. One example is the two populations of native turtles, the European Tortoise and the Leper Tortoise, which are “on the brink of extinction.”
This bad situation has become widespread in Doñana, as highlighted in the latest report on the state of biodiversity. Many animal populations are at historic lows, not to mention that the last winter was the worst in history, with 60% fewer birds. The negative trend mainly affects aquatic species, but also birds of prey (red kite and peregrine falcon), amphibians, butterflies and threatened flora.
