Marbella's reservoir dumps 20 times Costa del Sol's demand into the sea
La Concepción releases 28,000 litres per second as heavy rains push dam to safety limit
The Costa del Sol's La Concepción reservoir has been forced to release large volumes of water for safety reasons, despite recent droughts in the province.
Heavy inflows have pushed levels close to operational limits for the third time in less than a month.
The first release was when the inflow was 14 cubic metres per second. Just a few hours later, so much water was still pouring in from streams, tributaries and the tail end of the reservoir that operators were forced to double the outflow to 28 cubic metres per second.
To put those figures into perspective, 28,000 litres per second is almost 20 times the current demand of Malaga city and the Costa del Sol, which stands at around 1,500 litres per second in the low season.
La Concepción is well designed, but it's capacity falls short in time of heavy rainfall and consecutive storms, which have become a common phenomenon in the past couple of years.
The reservoir's capacity, in theory, is 57.62 million cubic metres. This does not mean that it will 'overflow', because there is always a buffer. Its maximum level in history is 62.5.
Nevertheless, the dam's operating rules are demanding and very safety-oriented. In the winter months and early spring a maximum of 48 million cubic metres is set to ensure a good margin in times of strong and fast inflows. For greater precision, these thresholds are set at a height above sea level (104.9 metres when maximum filling is allowed).
The reservoir was inaugurated in 1972. It collects the inflows from the Verde river and the triple transfer from the Guadalmina, the Guadaiza and the Guadalmansa. At one time, there were even plans for a further water transfer from the Genal, but this project, declared to be of general state interest, was shelved.
In 2016, a preliminary project proposed to build a connected dam further upstream. The idea was to increase overall capacity to 180 million cubic metres. The cost was 350 million. The project, however, was discarded for environmental reasons.
The Costa del Sol is now waiting for the Gibralmedina reservoir on the Guadiaro, between Malaga and Cadiz, to come into operation and receive 15 million cubic metres of already purified water per year. But the dam and its pipelines cost more than 700 million euros. In addition, the project has not been approved by the Ministry of Ecological Transition, nor has it received any sponsorship.
Geography
La Concepción is located between Marbella and Istán, where the 35-kilometre-long Verde river flows, with its source in the Sierra de las Nieves. The river's basin is 150 square kilometres. It flows towards the dam down a slope of between 22 and 13 per cent.
The Guadaiza comes from Igualeja (Serranía de Ronda/Sierra Bermeja), the Guadalmina comes from nearby and the Guadalmansa comes from between Faraján and Pujerra (Serranía). They all come together in the Behahavís-Estepona area and send water to the reservoir through diversion tunnels.
These days, in addition to the contributions from the upper basins, rainfall levels in the area have exceeded 60mm, according to the gauges of Guadalmina and Guadalmansa.
