Waiting for the procedures to continue until final approval, the scientific and technical team of the UCLM-Soliss Tagus Chair considers the minimum flows of the new Tagus Hydrological Plan to be insufficient in the middle section of the Tagus to achieve good environmental status.
Starting with Aranjuez, from this chair they point out that if the real flow of recent years is compared (see the blue line) with the minimums that have been established in the new Plan (red, orange and yellow lines), it is expected that to produce a certain improvement, since it will be mandatory that the real flows are higher than those that currently circulate. However, “this slight improvement will not occur immediately, but in three periods of time: first, until December 2015 (red line); then during 2026 (orange line); and lastly, from January 2027, the year in which the validity of the Plan ends (yellow line).
There is no legal or technical justification for establishing the minimum flow in three phases.”
They explain that «given that today the Tagus as it passes through Aranjuez is in poor condition, delaying the slight improvement with this timing harms the entire river ecosystem. And it has been established despite the fact that the area includes protected areas such as Sites of Community Importance (LIC) and Special Protection Areas for Birds (ZEPA), which also exist upstream and downstream.
Thus, four water masses of the Tagus River between Bolarque and Aranjuez have worsened their status in recent years compared to the first cycle, which indicates the need to establish higher minimum flows and establish the rest of the components of an ecological flow, such as periodic generating flows (those that allow natural flooding in the river floodplain). It is important to remember that the ecological flows with all their components are a tool contemplated in our hydrological planning to improve the state of the rivers.
In addition, "the minimum flows that have been proposed in this third planning cycle in these three water masses are very far from those proposed in the studies on which the lawsuits against the Hydrological Plan for the second cycle were based and which ended in the partial annulment of the Plan through five decisions of the Supreme Court (see the green line in the three graphs). These studies used methodologies based on compliance with the objective of good status, as well as on the achievement of the conservation objectives of their habitats and species of the Red Natura 2000 protected areas».
Prior to the proposal of new minimum ecological flows, "it would have been necessary to carry out an analysis of the consequences that the previous minimum flows have had on the state of the water masses (in terms of their morphology and the conservation of their habitats and species, differentiating the Red Natura 2000 areas)”, in order to correctly determine the needs of the river, as the researcher Domingo Baeza considers.
Likewise, the academic team of the UCLM-Soliss Tajo Chair considers that a greater ambition is necessary to be able to comply with the obligation to conserve these protected areas, the most suitable being the application of methodologies based on the simulation of habitats that seek to maintain 100 % of habitat. In protected areas, lower than that percentage would mean a deterioration of the habitat. It should be noted that there is a lack of knowledge about the habitat in some water masses, where scientific-technical studies are still necessary.
In conclusion, “for the Tagus River to achieve its good environmental status, an essential measure is to have minimum ecological flows that guarantee the maintenance of plant and fauna communities. Additionally, in Red Natura 2000 protected areas, the minimum flows must meet the specific requirements for habitats and protected species, so these may be higher.
The methods used to establish the minimum ecological flows must be the ones that are best adapted to achieve said ends, leaving aside other interests unrelated to the environmental objectives of the river. These methods must have in-depth knowledge of the habitat and its species, as well as the hydrological behavior of the river.
Finally, “it is more appropriate to establish minimum ecological flows in monthly series, instead of quarterly, to reduce the difference between the natural regime of the river and the regulated one in Mediterranean rivers. And more importantly, a monthly distribution is recommended that, in addition, establishes greater variations between some seasons and others, in order to achieve this reduction.