This week, the reservoirs in the Segura River basin reached 60% of their capacity, with 684 hm³ concentrated in the headwater reservoirs of La Pedrera in Orihuela, Fuensanta (Yeste), and El Cenajo in Castilla-La Mancha. According to data from the Ministry for Ecological Transition, one had to travel back eleven years to June 2015 in order to discover a comparable level in the Segura River basin.
Reports every week
Although it is now less noticeable than normal, the basin nevertheless stands out in the weekly hydrological data for falling behind the other districts on the Iberian Peninsula. When it comes to water reserves, this year is actually among the finest hydrological years in the first 25 years of recorded history. But in 2011, 2013, 2014, and 2015, the basin had a wet cycle with rainfall levels comparable to the current one, followed by nearly ten years of drought. The southeast Mediterranean region is characterised by this erratic and conflicting pattern.
The Segura’s headwaters
Two peculiar trends have come together to create this ample water situation. On the one hand, for almost a year now, transfers at the maximum monthly volume of 60 hm³ have been ensured by exceptional water reserves in the higher sections of the Tagus River. However, a hydrological year in the Segura River basin itself, which started in October 2025 at record lows, has allowed the upper reaches to recover from a situation where El Cenajo, this week at 273 hm³ and at 63%, and Fuensanta, now at 163 hm³ and at 78% of its capacity, were effectively dead reservoirs, with the meagre amount of water they held falling below the discharge intake.
The La Pedrera reservoir, which can contain 129 of its 244 cubic hectometres—an increase of four cubic hectometres in just one week—has surpassed 52% of its capacity. It was at 30% at the same time last year.
Because it receives nearly all of its water from the Tagus River transfer through post-transfer systems and desalinated saltwater production, this reservoir is also a crucial reference point. The Region of Murcia uses almost 80% of these water resources for irrigation.
Furthermore, of the 684 hm³, the Tagus-Segura Water Transfer directly contributes 253 hm³, or 37% of the total. The balance of water inflows and outflows to the traditional irrigation network and the transfer network is still positive, with 6 hm³ more in the last week, despite the agricultural sector’s increasing water demand by mid-May due to rising temperatures and citrus fruits ripening in the fields.
The network of dams contained 353 hm³ during the same week last year, which is about half of the current reserves and slightly over 30% of capacity. Over the past ten years, the average for this same week in May has been 414 hm³.
Transfer
The water storage levels at the Entrepeñas (Guadalajara) and Buendía (Cuenca) reservoirs at the Tagus River’s headwaters, which supply the Tajo-Segura Water Transfer, are still at all-time highs. Just weeks before the start of the meteorological summer, these two reservoirs, along with nearly all of the water infrastructure connected to the aqueduct, were constructed large and have seldom recorded levels like these.
They collectively store 1,628 hm³, which is more than 200 hm³ above the limit at which the transfer’s existing operational regulations permit a maximum of 60 hm³ to be transferred each month in the latter part of May. Buendía has 617 hm³, or 75% of its total storage capacity, whereas Entrepeñas has 1,011 hm³, or 60% of its capacity.
In contrast
The political and legal environment is very different from the hydrological situation on the ground. This is true in the receiving regions of Alicante, the Region of Murcia, and Almería as well as in Castilla-La Mancha, the water’s source basin. According to the draft of this update, the government would implement new operating regulations that would reduce annual transfers by 50%, from an average of just over 200 cubic hectometres per year during the 47 years of the aqueduct to about 100. The agricultural sector in these areas is fighting to stop the government from consolidating the increase in ecological flows. More than 80,000 irrigators are supported by the transfer, which is augmented by treated and desalinated effluent. It creates 100,000 jobs and adds about €4 billion to the country’s GDP. The province of Alicante is home to about 25% of these jobs.
The Taibilla Canals Association, which has been supplying the rising demand with desalinated water for years despite the volume of water transported remaining constant, completes the supply need of the major cities in the southeast with an additional 100 cubic hectometres annually.
Given that the present basin plan was authorised in January 2023, Castilla-La Mancha and the riverside towns along the headwater reservoirs are requesting that the government update the operational rules to implement this cut-off step immediately. The water transfer, according to the riverside municipalities, has fuelled an intense irrigation business that they deem environmentally unsustainable.
