● This June, the flow of the Tagus River has dropped alarmingly, below the legal minimums
● The problem is not a lack of natural contributions, but rather the insufficient release of water in the headwater reservoirs.
● It is necessary to change the Exploitation Rules of the Tagus-Segura transfer to guarantee the priority needs of the transferring basin
● There is no justified reason for the flows in the Tagus River to fall below the established legal minimum.

In recent weeks, the flow of the Tagus River in its middle section has visibly decreased. In Toledo, the flow of the river has dropped so much that it cannot overcome the Safont weir. Throughout the city there is only a succession of stagnant water that makes it difficult to maintain the ecological conditions of the river.

The situation is more serious downstream, past the Castrejón reservoir, as the Tagus River approaches Talavera de la Reina. At the Automatic Hydrological Information System (SAIH) station that the Tagus Hydrographic Confederation has in the municipality of Cebolla, alarming drops in flow below 3 m3/s are being recorded. This is equivalent, in a river with a channel width like the Tagus, to barely circulating water. As it passes through Talavera de la Reina, since June 12, there are times when the flow of the Tagus River is below the 10 m3/s established as the minimum legal flow.

There is no justification to go below the legal minimum

Article 59 of the Water Law gives ecological flows priority over all other uses. That is, they must be respected in any circumstance, except for exceptional issues of water scarcity for human supply.

Although the minimum flows in Aranjuez, Toledo and Talavera are repealed by the rulings of the Supreme Court (TS) of 2019, flows below that minimum should not circulate, since the TS considered these flows insufficient to guarantee the environmental objectives of the Tagus River. It is logical, therefore, that, until the definitive establishment of new, more ambitious ecological flows, these cannot be less than 10 m3/s in Talavera de la Reina.

Why has this anomalous situation occurred?

The alarming decrease in the water level that we observed these weeks is due to an insufficient release of water from the Entrepeñas and Buendía reservoirs, upstream. The discharges from the headwaters must be used to satisfy all the needs of the Tagus, including irrigation, which is more abundant at this time of year. Although there is a monthly limit on the amount of water that can be released from the headwaters to the Tagus itself, set in the Memorandum, in the Rules for Exploitation of the Tagus-Segura Transfer, managers can exceed it due to environmental requirements with due justification.

During the summer months there is an increase in agricultural demands in the middle zone of the basin which, due to the priority of the transferring basin, must be satisfied. These agricultural demands are included in the hydrological planning and, therefore, are adapted to the amount of existing resource, always taking into account compliance with the minimum flows. Regardless of whether an evaluation is pending on the efficiency of these irrigations or whether the extension of the irrigated surface is the most sustainable for the good condition of the Tagus River, at this time the minimum flows are not being guaranteed. The decreases in flow to which the river is being subjected in its middle section are incompatible with the maintenance of river fauna and vegetation. The Tagus River is slowly being exhausted and it is not because its basin lacks natural contributions.

Paradoxically, the Exploitation Rules of the Tagus-Segura transfer define the waters that are derived from its headwaters to the Segura as surplus from the Tagus. This makes no sense, given that the discharges that are being produced from Entrepeñas and Buendía to the Tagus are not sufficient to meet the basic environmental demands of the Tagus River itself in the Talavera de la Reina area, which are a priority over those of the rest of the region. applications. It is necessary, at a minimum, to modify the Operating Rules of the Tagus-Segura transfer with regard to the maximum discharges to the Tagus. It is the only river in Spain that has a limit by law on the amount of water that can circulate through it.

In short, there is no justified reason for the flows in the Tagus River to fall below the established legal minimum.