The \u00a0drought\u00a0 has been a \u00a0recurring topic\u00a0 over the past few years, taking center stage in the informational agenda due to the \u00a0lack of rainfall\u00a0 and its myriad consequences. This ongoing situation begs the pressing question: \u00a0how much water do we have left?\u00a0 The inquiry, however, leads to a troubling realization: we are not truly equipped to answer it.<\/p>\n
What is abundantly clear is that our \u00a0water reserves\u00a0 typically fall short of what official data suggests. This discrepancy arises from natural processes such as \u00a0erosion and sedimentation\u00a0, the ramifications of which have long concerned experts in the field. <\/p>\n
Throughout their course, rivers transport small particles of rock and \u00a0organic matter\u00a0 that tend to accumulate at specific points along their journey, whether on the riverbed, in delta formations, or in their meandering paths. Reservoirs are another prime location where water tends to “release” these particles.<\/p>\n
The floors of reservoirs tend to accumulate \u00a0silt\u00a0. The primary problem this creates is the loss of the reservoir’s capacity. The greater the volume of the reservoir occupied by sediments, the \u00a0less water\u00a0 it can store.<\/p>\n
A second concern is that we do not have a precise understanding of the \u00a0rate of sediment accumulation\u00a0 in each reservoir, as this can vary based on the characteristics of each watershed and reservoir. Without this knowledge, we are left in the dark about \u00a0how much water remains\u00a0.<\/p>\n
Estimations regarding sedimentation\u2014commonly referred to as \u00a0siltation\u00a0\u2014vary significantly. A \u00a0bathymetric study\u00a0 conducted in 2018 by the \u00a0Tajo Hydrographic Confederation\u00a0 in the Entrepe\u00f1as and Buend\u00eda reservoirs suggested that sediment build-up was negligible.<\/p>\n
Conversely, another bathymetric study, undertaken by the \u00a0Segura Hydrographic Confederation\u00a0, estimated that its reservoirs could have lost between \u00a010% to 40%\u00a0 of their capacity due to this phenomenon. Notably, they highlighted the Lorca reservoir, built at the end of the 19th century, as being on the upper end of this spectrum.<\/p>\n
Estimates for all Spanish reservoirs remain limited. A study encompassing \u00a0110 reservoirs\u00a0 indicated that the loss of capacity could be around \u00a05%\u00a0. Jos\u00e9 Luis Casamor and Antoni Calafat from the \u00a0University of Barcelona\u00a0 cautioned that the uncertainty surrounding this estimate is quite high, given that the potential to extrapolate these results to over a thousand other reservoirs is limited.<\/p>\n
This issue is one that experts have been warning about for \u00a0years\u00a0. For example, the study conducted in the Segura basin was carried out in \u00a02017\u00a0, while the work by Casamor and Calafat was published in \u00a02018\u00a0 in the \u00a0Tierra y Tecnolog\u00eda\u00a0 journal of the \u00a0Official College of Geologists\u00a0.<\/p>\n
In a subsequent article published in \u00a02018\u00a0 in \u00a0The Conversation\u00a0, Casamor explained that the problem of sedimentation presents \u00a0“expensive and complex solutions.”\u00a0 Cleaning the sediment from reservoir beds is a daunting task that necessitates emptying the reservoir, a process made even more complicated in older reservoirs.<\/p>\n
Experts like Casamor advocate for \u00a0preventative measures\u00a0. These involve integrating knowledge about sediment accumulation during the design phase of infrastructure projects. One suggestion includes the addition of \u00a0dikes\u00a0 upstream from reservoirs to catch sediments before they reach the reservoirs.<\/p>\n
Additionally, proposals have emerged for \u00a0upstream sediment control\u00a0, which includes \u00a0reforestation\u00a0 efforts. Plants help reduce soil erosion, thereby decreasing the number of particles that reach rivers and ultimately reservoirs. In this context, the phenomenon of \u00a0rural abandonment\u00a0 has also been partially held responsible for the current state of affairs. Furthermore, wildfires contribute to sediment runoff into waterways, emphasizing that mitigating those effects can aid in lessening the problem.<\/p>\n
As the water crisis continues to pose challenges, addressing sedimentation in reservoirs has become imperative for the sustainable management of water resources in Spain.<\/p>\n