Vast underground 'reservoir' near Malaga Airport will start supplying the city with water this summer

Malaga city has an enormous opportunity to exploit the large underground 'reservoir' located in the Bajo Guadalhorce area. Planned work to recover the wells is almost complete. It is estimated that in July this year, public water company Emasa will be able to start using them for urban supply, given that they are connected to the desalination plant at El Atabal. However, it is essential not to 'kill the goose that lays the golden eggs', which is why Emasa has put out to tender an important contract to monitor what is happening in this alluvial aquifer minute-by-minute during the first two and a half years.

Initial estimates point to a flow between the five wells (three in Perales, Santa Teresa industrial area, and two in Puente del Rey, near Malaga Airport) of up to 900 litres per second. This is more than half of the flow through the city's water supply network. But that is the nominal flow - the maximum capacity, to put it simply. It's not a reservoir, but it can supply as much as one. However, underground water sources come with a risk: their quantity and quality can drop very quickly. For example, they can become saline or they might absorb pesticides and undesirable chemical substances.

For this reason, the activated consultancy contract involves a lot of chemical and laboratory parameters. It is a matter of starting to use these resources as a complement: to have their infrastructure of wells, intakes, extraction systems, pipelines and electricity well-maintained, and, in short, to have them 'fine-tuned' for a new drought situation.

Emasa, with the experience of the network of wells of Aljaima and Fahala (Cártama), prefers to have an indicator that recommends a flow rate for exploitation. In the first instance, given the good level of the reservoirs, use will be limited to a few hundred litres per second.

It is important to note that this new supply source becomes part of a global system with the three headwater reservoirs (Guadalhorce, Conde and Guadalteba), the two flood abatement reservoirs that may also supply water (Limonero and Casasola), and the aforementioned wells and boreholes in Cartagena.

The planned commissioning is scheduled for this summer. Right now, something unusual is happening for this time of year: Aljaima, between the flow from the Guadalhorce river (coming from the Grande) taken at the weir, and the network of wells on both banks, is contributing up to 600 litres per second. In addition, the water from Casasola and Limonero is being used more than usual. In both, especially in the former, it is important to reduce the volume of water in the reservoir in order to proceed with the extraction of sludge and the recovery of the dam's outflow organs.

This is not the first time that the municipality has resorted to external experts to evaluate a resource that is difficult to manage and that needs to be well-understood. In fact, such knowledge is often a pending subject in water management. In the past, the city council has relied on the expertise of Professor Bartolomé Andreo, from the hydrogeology centre of the University of Malaga.

The tender now being launched is for more than 300,000 euros, including Spain's IVA sales tax. The contract has a completion period of 30 months. "It will allow the controlled use of this alluvial aquifer, the flow of which ends up in the sea," the city council said. The deadline for submitting bids is 12 June.

This monitoring will be undertaken in parallel with the entry into service of the Perales (two) and Puente del Rey (three) wells, which fell into disuse and which will be incorporated into the Aljaima and Fahala wells that have been progressively activated since June 2023. Groundwater has saved 33% of reservoir water in the last year.

The recovery of the Perales and Puente del Rey wells is included in the emergency works approved by the Andalusian regional government to improve water resources in the face of the drought crisis, with an investment of more than 15.4 million euros. So while Emasa undertook the conditioning of these five wells with an investment of 2.3 million euros, the regional ministry of agriculture, fisheries, water and rural development has been responsible for the execution of the necessary pipelines to transport the extracted water to the existing reservoir to the north of the airport and, from there, to the pipes that connect with the main network to the drinking water treatment plant at El Atabal.