Doñana National Park irrigated with polluted river water

by Deborah Cater
Doñana National Park
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A greatly increased concentration of harmful nutrients has been found in the river water that ends up in the groundwater of the Doñana National Park. In the long term, this can cause irreparable damage to the park’s ecosystem.

The watering system in the park itself is under permanent supervision. However, the continued existence of the park also depends on the quality of the water outside this system. A sample of the Ecology Department of the Wetlands Doñana (part of the Spanish Council for Scientific Research CSIC) showed the river water in the vicinity of the park is highly polluted. 

Not compatible with life 

It concerns a surplus of nutrients such as nitrates and phosphates, causing so-called eutrophication. This phenomenon has already caused great damage to the Mar Menor in Spain and is now also a threat to the Doñana National Park. According to the CSIC, the concentrations of pollutants are so high in a number of places that they are no longer compatible with the life of the park’s flora and fauna in the long term. 

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Agriculture fivefold in 25 years 

For three years, the study analysed the concentration of nutrients in the supply river water at 56 different points. Subsequently, they added data on the increase in agricultural greenhouses in the area to the results from these analyses. This showed the area of ​​agricultural land has increased by no less than 487% since 1995. Rainwater carries the waste products from these greenhouses, after which they end up in the groundwater of the Doñana National Park. If concentration of these substances becomes too high, natural biological and chemical processes are no longer able to counteract pollution. 

Natural solutions 

The situation is worrying because on the one hand intensive agriculture is still difficult to reduce. On the other, pollution occurs in places where the water quality for the park is not monitored. Research leader Irene Paredes therefore argues for these checks to be carried out in areas outside the park itself. In the short term, green filters could be installed that block the nutrients in the water. According to a study published in Nature Sustainability, measures such as modifying the agricultural drainage system can reduce nitrate concentrations by 25% to 78%. 

A research team from the University of Seville is investigating the possibilities of a natural cleaning mechanism. The mechanism, with about 150 strains of bacteria, can lower the nitrate concentration in the water. This will protect the ecosystem against other pathogens. 

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