Malaga's Reservoirs In Spain Face Significant Water Loss Through Evaporation

Malaga's Reservoirs In Spain Face Significant Water Loss Through Evaporation

Malaga's Reservoirs Face Significant Water Loss Through Evaporation Amid Climate Challenges

Malaga, May 27, 2024 — Malaga province's reservoirs are experiencing significant water loss through evaporation, with over 30 cubic hectometres (hm³) evaporating in years with average rainfall, according to the Junta de Andalucía's latest drought committee report. This volume of water is enough to supply the city of Malaga, with its population of 450,000, for more than six months.

The exact amount of water lost to evaporation varies based on multiple factors, including rainfall volume, temperatures, and the surface area of the water. Higher rainfall leads to greater evaporation due to increased water surface exposure. This trend is particularly concerning given that 2023 was the second warmest and sixth driest year on record for Malaga since 1961. Although this year is projected to be slightly wetter, it is also expected to be warmer.

Specific Reservoir Impacts

Viñuela Reservoir:
The Viñuela reservoir in La Axarquía can lose up to 11 hm³ annually during normal rainfall years but only 2.41 hm³ during drought conditions. The evaporation rate is influenced by factors such as the mirror surface (the water surface area), temperatures, hours of sunshine, and rainfall.

Guadalhorce System:
In the Guadalhorce-Limonero system, with an average annual rainfall contributing 64 hm³, approximately 20 hm³ evaporates. This evaporation decreases to 15 hm³ with half the rainfall, 10 hm³ with a quarter, and around 5 hm³ during droughts. For instance, during a particularly dry period last year, the system lost 2.05 hm³ to evaporation between October and January.

La Concepción Reservoir:
La Concepción reservoir, located between Marbella and Istán, experiences lower evaporation due to its smaller size. In a typical year, it loses about 2.5 hm³.

Broader Concerns and Scientific Insights

Evaporation contributes significantly to water loss in reservoirs, a phenomenon exacerbated by global warming. Dr. Enrique Salvo, a botany professor and climate change expert, highlighted that the Alboran Sea area is among the fastest warming regions globally. He noted that both human consumption and natural evapotranspiration significantly impact reservoir levels, especially under extreme temperatures and wind conditions.

For example, the Guadiana basin, with a capacity of 9,538 hm³, loses approximately 230 hm³ annually to evaporation. In the Júcar basin, losses can reach 0.3 hm³ per day during peak heat.

Mathematical Modeling and Potential Solutions

The Penman equation, which factors in net radiation, wind speed, air temperature, vapour pressure deficit, curve slope, and ground heat flux, is commonly used to model evaporation rates.

Innovative Approaches to Mitigate Evaporation

Currently, there are no definitive solutions to curb evaporation from large bodies of water. However, several experimental approaches are being tested worldwide. These include using chemical treatments and partial covers. One innovative proposal from Trops and the University of Malaga involves installing floating solar panels on La Viñuela reservoir. These panels would not only supply energy to a proposed desalination plant but also reduce sunlight exposure on the water surface, thereby reducing evaporation.

Reservoir Status

As of now, Malaga's reservoirs have gained 73 hm³ from March rains, reaching a total storage of 170 hm³. However, this amount has recently decreased to 167 hm³, which is only 27% of their total capacity.

In summary, while the challenges of evaporation in Malaga's reservoirs are significant and complex, ongoing experiments and innovative proposals offer hope for mitigating these losses in the future.

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