Abstract
The physical limnology of a shallow pond system was characterized using field measurements of water temperature, pH, and electrical conductivity (EC). We determined the spatial variability in surface and groundwater temperature, pH, and EC along the pond’s shore and along the several pond-shore transects, analyzed the water column temperature gradient and estimated the groundwater discharge rate using a heat transfer model. The fieldwork was conducted in Santa Olalla and Dulce ponds located in Doñana National Park in southwestern Spain during different stages from 2016 to 2018. The results of this study have improved the understanding of the thermal structure and the surface–subsurface heat exchange in the ponds and highlighted the importance of groundwater discharge in the pond water balance. It also showed the heterogeneous nature of groundwater discharge through the bottom sediments of the Santa Olalla pond. These results are consistent with previous studies and strengthen the existing hydrological and limnological knowledge of these ponds located in the protected area which is receiving a great deal of public attention.
Highlights
Doñana, in southwestern Spain, is an iconic World Heritage site within the Mediterranean region.The conservation of this ecosystem is challenging, requiring coordinated actions across complex and sometimes very large watersheds
This study has shown that the groundwater inputs to Santa Olalla pond had high seasonal variability
The results obtained by these authors indicate that Santa Olalla acts like a discharge pond during the wet phase of a hydrological cycle (December 1985), but they point to an inversion of the hydraulic gradient during the dry phase (July 1985), in which a water recharge toward the aquifer takes place, bringing salts via advection methods
Summary
In southwestern Spain, is an iconic World Heritage site within the Mediterranean region. The conservation of this ecosystem is challenging, requiring coordinated actions across complex and sometimes very large watersheds. Doñana is still affected by a range of threats. Water extraction and pollution have caused the degradation of a number of ponds within the wetland complex in spite of their protected status [1]. The Doñana area is located on the Atlantic Ocean coast, adjacent to the Guadalquivir River mouth (Figure 1a), and covers more than 3000 km. Inside the limits of the 543-km Doñana National Park is the Doñana
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