The latest rains have barely managed to recover the Doñana marshes
The Doñana Biological Station CSICthrough the ICTS-Doñana Biological Reserve and the GIS and Remote Sensing Laboratory, has compiled the precipitation data of the meteorological stations found in the park and in the surrounding area, and has used the latest satellite images and drone flights to estimate the flooded surface.
Although the municipalities around Doñana have experienced somewhat higher than average rainfall, the situation is different within the National Park.
The stations of Almonte y Chipiona of the Agroclimatic Information Network of Andalusia have recorded during the months of September and October an accumulated rainfall of 125 and 131 liters per square metervalues that are well above the average of the last 20 years.
It is when the aquifer is recharged by the rains and the water reaches the surface, when the lagoons begin to flood.
However, the data from the Doñana Palace stationwhich is located in the heart of the Dan National Park much less precipitationof 72 l/m2, which is below the average of the last 20 years.
Likewise, the six automatic weather stations that the ICTS – Doñana Biological Reserve has, which provide data continuously every five minutes, give an average precipitation in September and October of 87.7 l/m2, figures far from those recorded. in Almonte and Chipiona.
LOW FLOODING OF THE MARSH
The differences in precipitation in the Doñana environment and those that have occurred within the park have generated different situations.
The image of Sentinel satellite 2 of November 7, which clearly show the state of flooding of the cloudless marsh, allow us to appreciate that the first flooded areas have been the marshes of El Rocío and Los Sotoswith a flooded area of 188.8 ha.
These images also allow us to estimate that The total flooded area of the Doñana marsh is currently around 537.8 hectareswhich represents 1.8% of its total area.
It is a value that is found something below average on these dates. In addition, some flooded areas have been detected in the King's Lucio and the Pike of Veta Tongueas well as on the border of the marsh with the river and the Tower Armalthough these are due to tidal influence.
SANTA OLALLA AND THE AQUIFER
The precipitation that has fallen to date is allowing the hydration of the clays that form the substrate of the marsh and additional rainfall will be necessary so that the total flooded area increases.
The situation in the lagoons is different. While the marsh sits on clay soils and is nourished only by surface waters, the Doñana lagoon system is located in a sandy area and its Flooding depends on the water in the aquifer and its water table..
Is when the aquifer is recharged by rain and the water reaches the surface, when the lagoons begin to flood.
On these dates the Santa Olalla lagoon is also offering the first signs of recovery. Santa Olalla was the largest permanent lagoon in Doñana. However, the overexploitation of the aquifer and the low levels of precipitation that have been recorded for more than ten years, ended up dry it completely during the last two summers consecutively, which had never happened since records began.
As of November 7, the lagoon had approximately 7 centimeters depth measured on the scale located to the east. The images obtained with a drone allow us to estimate a flooded area of 49 hectares, which represents 9.6% of its maximum area.
