Wednesday, December 7

“The priority is always to maintain the urban water supply”


The almost dry bed of the Camba river in Orense, seen from a drone. / EFE

The scientist of the Panel of Experts of the United Nations and the CSIC, Sergio Vicente, warns that the biggest problem facing Spain is the increase in temperatures

Domenico Chiappe

“Drought is not unusual, it is something characteristic of the Mediterranean region in which we find ourselves,” maintains the scientist from the Pyrenean Institute of Ecology Sergio Vicente, a member of the United Nations Panel of Experts on Climate Change (IPCC) and the Center Superior for Scientific Research (CSIC). “We cannot say that this year there is an extreme event. There is a lot of confusion. The amount of water resources depends on how the weather conditions have been in the previous months, in winter and spring. If we have a rainy season, the reservoirs are well recharged and there will be no problems coping with the irrigation campaigns, which are the ones that demand the most water. And this year we have had a very dry winter.

More than the rains or the drought, the “important” problem facing Spain is the increase in temperatures since the 1950s. “The high temperatures make the drought more severe because the crops demand more water when the atmosphere is warmer,” explains Vicente. “In addition, there is more evaporation of water. We cannot say that there are more droughts, from a pluviometric point of view, but rather that they are becoming more and more severe due to the increase in temperature.

Is a water scarcity scenario expected? “Scarcity refers to the lack of water to meet certain demands,” answers the scientist. «I would not be catastrophic that there will be no water. There will be years when the availability of water is less and others are more humid. Everything will depend on the rainfall.

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However, “we can predict what is going to happen tomorrow, in three days or a week, but in 15 days or three months we cannot predict the drought with current models,” says Vicente. “Therefore, it is important to know the severity of droughts and this is done through a monitoring system. Knowing if the conditions are anomalous or not in a given region allows mitigation measures to alleviate the consequences to be as efficient as possible.

Measures for adaptation

The situation does not justify the warning of water cuts in populated centers. «The urban demand for water in Spain is almost 15% and the cost of irrigated agriculture is around 85%. The priority is always to maintain the urban supply. To reach a cut in consumption, the situation must be critical like that of the 1990s, when there was a drought for three consecutive years. Right now in some rural areas there is a certain conflict between human consumption and that of vegetation. There are headwater areas, where the sources dry up, but not because it rains less, but because before there was no vegetation to consume that water».

-What are the possible climatic scenarios?

-What future climate change models show is that rainfall will decrease, but there is a lot of uncertainty in the case of rainfall. According to this, the rains should have dropped a lot in the last 150 years and it hasn’t happened. What is clear is that temperatures will continue to rise. Due to variability, if we have a period of drought and, in addition, we have one or two more degrees, things are not going to go well because the vegetation will be more subject to greater stress or there will be more evaporation.

-Does this affect agriculture in an important way?

-The annual rainfed cereal harvests, which are the traditional ones, are in June. Therefore, the atmospheric demand in spring is not very high, so they will not be very affected. Other permanent crops such as olive groves or vineyards will suffer greater water stress in summer. Irrigated crops, which consume a lot of water, will be seriously affected if this availability does not exist, they may be at risk of crop failure or not being able to be cultivated.

– Is the situation of natural parks similar?

-In the case of the vegetation of the mountain headwaters, where the largest number of natural parks and protected areas are located, it is advancing due to the abandonment of agriculture and livestock activities throughout the 20th century. Therefore, the flows are dropping a lot because the vegetation consumes water and needs to transpire for its physiological processes. It’s not climate change. There is more vegetation and due to the high temperatures they demand more water.

-What measures would be effective for adaptation to climate change?

-We are carrying out research projects to find out how management measures for natural spaces, forests or grassland areas can increase the availability of water resources and, in addition, have other types of services from an ecosystem point of view. For example, if grasslands are well grazed they can sequester more carbon, reduce erosion or better maintain ecosystems. A measure of adaptation to climate change is good forest management, which is now practically non-existent in Spain. Landscapes have changed, in the last 100 years, from being agricultural or ranching to being natural landscapes with a lot of vegetation, which consumes a lot of water and presents a very high risk of burning.

-What other measures can work?

-Reduce the demand of sectors that consume more water, such as irrigation. But it is problematic because it has been seen that when irrigation systems are modernized they do not return the water, but use it on other surfaces. We are talking about a productive sector that seeks the highest possible profitability.

-And build more desalination plants or more reservoirs?

-They are very sensitive issues, it is not something trivial. We are in a cycle where the construction of a large number of public works is not on the table. This was a policy of 60 years ago, but it had consequences on the river courses and the most fertile areas were flooded. So it cannot be argued that the sacrifice is always from the areas where the water resources are produced. In the case of desalination plants, in island areas, the Canary Islands or the Balearic Islands, where there is a high demand for water, this is a solution, but they also require a large amount of energy, which is not free. All of that is weighed. It is necessary to modernize crops, improve the management of pastures in semi-arid zones, optimize agricultural activities.


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