The nitrates in the Mar Menor come from various sources. On the superficial route, both farm runoff and the surfacing of groundwater polluted by fertilizers has reached the lagoon run through the creeks. Underground, the connection between this aquifer and the Mar Menor provides another route. Exact nitrate contributions to the Mar Menor along this route are currently being calculated. The Mar Menor has also been affected by wild urbanism, the building of too many marinas and the dredging of the Estacio channel to allow ships with deeper draughts to pass through.

Causes are many but the central role of the agricultural sector is clear. The question of who will pay for the measures to end the damage on the Mar Menor is another story. What we already known is that it will neither be immediate nor cheap.

In the framework of the 'Topillo Case', the Public Prosecutor's Office emphasized that years ago the budget of the necessary measures to avoid the eutrophication of the Mar Menor has already been detailed. The 2009-2015 Segura Basin Hydrological Plan envisaged an investment of 425.5 million euros, including 33.4 million to reduce the entry of nutrients into the lagoon; 51.4 million to reduce irrigation returns; 9.1 million to seal wells and avoid cross- contamination of aquifers; and 20.3 million to collect discharges from desalination plants that ended up in Albujón creek. Very few of all planned measures were actually carried out, but the Public Prosecutor's Office notes that, according to the 2015-2021 Basin Plan, out of these four specific ones a net total of zero was executed.

In March 2019, the Ministry of Ecological Transition published a document called "Analysis of solutions for zero discharge from the Campo de Cartagena into the Mar Menor", after submitting it to public consultation. The first thing the document does is admit what has happened: that "the Mar Menor has undergone a process of nutrient enrichment produced as a consequence of human activity, causing an alteration of its natural conditions" and triggering "an explosive-type trophic crisis" which has caused "the ecological stability and resilience capacity of the Mar Menor to be limited, being very much conditioned by events that may produce disturbances and increase the degree of stress", as in fact happened after the last series of cold fronts.

The Mar Menor's resilience eventually turned against it. Nitrate measurements on the west coast, especially around the Albujón creek, showed already worrying nitrate levels in 2010 and 2012, but the waters remained nonetheless transparent.

The Ministry's document uses, in the second half of 2015 words like: "drastic change", "environmental collapse". Starting in 2016, nitrate concentrations in the lagoon skyrocket. 85% of the initial extension of the seagrasses is lost, with only those in the shallower and therefore more illuminated parts resisting. Invertebrates mortality also skyrockets. Phytoplankton gains exponentially in size, as does the amount of its excretions, which produce foam, an intense green colour and decomposition of organic matter in the water.

The document recognizes that "it is necessary to revert this situation by eliminating or minimizing impact factors on the lagoon.” Incredible as it may seem, the key to the solution is to a large extent to again do what was left half done and was finally dismantled when the green colour of the Mar Menor made the alarms go off.

The first thing will be to desalinate and denitrify the waters of the Quaternary aquifer, extracting 12 hm3 per year (amount to be reviewed when the exact volume of Quaternary aquifer water that can reach the Mar Menor through the underground connection is better known). The process will happen in the original plant designed for this purpose, the Mojón desalination plant, and in the Arco Sur plant. The desalted water, now suitable for irrigation will be delivered to the irrigators while the brine, already denitrified, will be poured into the Mediterranean by means of two outfalls.

Unregistered wells causing cross-contamination between aquifers will be closed according to a management programme and groundwater extraction will be centralized.

With regard to irrigated land, the document states that "beyond current legal processes, the lawfulness of all concessions and farmland, as well as the management of their discharges” should be reviewed.

The document accepts the figures of irrigated farmland that environmentalist associations have reported for years and that differ from those in official reports. They state that, between 1988 and 2009, irrigation in the basin increased from 25,150 ha to 60,700 ha and that an increase of "between 15,000 and 20,000 ha of current official figures is estimated".

647 millon
COST OF MEASURES

The Environmental Impact Statement has been approved in September 2019, allowing for the immediate execution of the measures.

The project will be carried out over a decade and will cost 647 million. It will be funded by the Government of the Region of Murcia, the Ministry of Ecological Transition through the CHS, the Associations of Irrigators and the owners of the wells.