Drought doubles salt content in Guadalhorce reservoir, forcing more investment in Malaga water treatment plant

Drought is on its way to becoming part of the fixtures and fittings of the Andalusian landscape. Unfortunately that does not only mean a quantitative lack of water. The region's water resources are worsening and increasingly require more sophisticated treatment procedures. One of Malaga city's strategic reserves, the Guadalhorce reservoir, has always been subject to salinisation from waters coming from the Meliones spring. However, this phenomenon has worsened over the last two years. This has led Malaga's municipal water authority (Emasa) to put more effort into investing in El Atabal desalination and water treatment plant. The latest investment involves renewing the plant's reverse osmosis membranes (a fancy filter, a semi-permeable membrane that allows water molecules to pass through, but not dissolved salts and bacteria, among others). The tender has been awarded to the specialised company Peak Spain for 1 million euros (IVA, Spain's sales tax, included). It is not only a question of treating the water more effectively but of saving energy and extending the life of the components.

With these emergency fixes being pushed through by the region's agricultural ministry, the treatment capacity of these facilities increased by 12%. This involved an investment of 2.3 million euros. The work lasted just over a year. The intention now is to gain another 10% with a second wave of improvements.

The salt content in the Guadalhorce now exceeds 4,000 microsiemens per centimetre (uS/cm). Electrical conductivity is a measure of the saltiness of the water and is measured on a scale of 0 to 50,000 uS/cm. Fresh water is usually between 0 and 1,500 uS/cm. The Guadalhorce at 4,000 uS/cm is equivalent to 2.56 grams of salt per litre of water. The measurements are taken at the Paredones weir where the irrigation channels separate from the water supply that goes to Malaga city. In 2022, with considerably more water in the reservoir group, the figure was about 2,000 uS/cm. That 2,000 is about 1 gram per litre, which is what the irrigation channels can handle. In any case, the desalination plant could treat up to 10,000 microsiemens. But the more effort needed, logically, the higher the energy costs and the shorter the useful life of the plant's equipment.

It just so happens that it is not only the reservoir's waters that need treating, it is that the uphill strategy of searching for more wells sometimes implies uncovering water sources that turn out to be of lesser quality. This is the case of the waters that will come from the recovery of six wells in the Bajo Guadalhorce area (currently in the project-planning phase and building work allocated) and those that are gradually being set up in the area around Aljaima and Fahala (Cártama). All these together will be capable at times of ensuring full supply to Malaga city depending on rainfall and available reserves.

It is a chemical fact, verifiable by analysis, that Malaga delivers high quality tap water on a par with your average bottled water thanks to El Atabal. The analysis done on Wednesday 24 July, for example, showed a conductivity (salt) score of 526 (the sanitary limit for drinking is 2,500). In the case of water hardness (limescale), it was at 106, practically soft water. This is taking into account the poor quality of the water at source, which is what historically made Malaga's water very bad until 2005, not only because of its taste, but also because of the damage to household appliances and pipes with limescale build-up.

That is why it is essential to have the desalination plant, inaugurated in 2005, fully upgraded. Also that is why the membrane filters will be replaced gradually over the course of a year in order to affect production as little as possible.

The replacement of the reverse osmosis elements amounts to no less than 9,828 of them. If we were to spread these membranes out flat, they would occupy an area of 51 football pitches. This gives readers some idea of the scale of the upgrade to be completed.

As filters their periodic replacement is part of the maintenance of the whole installation. They are, in practical terms, consumables. Their life cycle depends on how hard they have to work, including when the incoming water worsens in quality. "Their need is of prime importance in achieving the potability and quality of water required for the city of Malaga," states the technical report that supports the investment.

The report reminds us that Guadalhorce reservoir does not even have water ready to be made into drinking water due to the aforementioned salt contamination. Furthermore, the situation has worsened over the last two years. This affects Malaga, of course, but also affects the water used for irrigation purposes, which has now been restricted. Irrigation supplies cannot exceed one gram of salt per litre, so it is necessary to draw from other reservoirs or mix supplies for such irrigation. Currently it is brine water that is discharged into the reservoir. Of course, should the water level go down further, the salt concentration goes up. The reservoir is only storing 18.5 cubic hectometres at present, half of last year's level. That isn't even 15% of its full capacity.

The value of this reservoir is strategic, for use in an "emergency" situation, according to the aforementioned report. In addition, if the membranes are not in optimal condition, more electricity will be consumed.

Regarding a second extension of the desalination plant, the work needed - valued at almost 30 million euros - has been authorised by Acuamed, the company that owns the facility. This was communicated to the Regional Ministry of Agriculture during their round of bilateral meetings. However, the financing of the project is still up in the air as central government does not seem to be willing to undertake it.

Another long-term project consists of converting the Pilones water treatment plant (next to the Málaga TechPark (PTA) and Tomillar dam) into a sort of twin of El Atabal to replicate the operation for growth in Malaga, the Guadalhorce valley and the wider metropolitan area. The construction project is due to be put out to tender in the coming months.