- The water crisis in the central and southern basins of Chile over the past decade has been mainly caused by mega-drought and climate change, as stated in the Report to the Nations developed by researchers from the Center for Climate Science and Resilience at the University of Chile (CR2).
- Due to the increasing trend in water consumption, an adverse scenario is predicted where most of these basins will face permanently high and extreme levels of water stress by the middle of the century.
By: CR2 Communications
“The uses of surface and groundwater are approaching or exceeding water availability in basins in north-central Chile. This generates socioeconomic and ecological impacts and poses an intergenerational dilemma as we move towards depleting reserves (or day zero),” warns the report “Water Security in Chile: Characterization and Future Perspectives,” presented last November by the Center for Climate Science and Resilience CR2.
The report also outlines the levels of water security during the 21st century in the context of climate change. It provides specific recommendations to move towards water security, considering the territorial reality regarding water use, availability, and governance.
In simple terms, water security is defined as the possibility of accessing water in adequate quantity and quality for human sustenance, health, and socioeconomic development, considering the ecosystemic particularities of each basin and promoting resilience against threats such as drought, floods, and pollution.
The report describes Chile’s current state, establishing that the high levels of water stress in central Chile, where the main source of supply is fresh surface water, suggest that the country’s central zone would be close to “day zero,” described as the moment when water demand can no longer be satisfied due to a lack of availability.
On the other hand, the absolute day zero is the moment when groundwater reserves are depleted in addition to surface sources. According to the report, “Unlike the time it takes to deplete the water from a surface reservoir, estimating the time to deplete groundwater reserves and reach an absolute day zero is uncertain, as it depends on variables that are difficult to quantify precisely, such as the volume of the aquifer, as well as the rates of recharge and extraction of groundwater.”
However, partial or total aquifer depletion represents extreme environmental damage due to the long recharge times. The report states that “this situation also poses an intergenerational justice dilemma because, if the unsustainable use of these resources is not reversed, a future generation will be the one to face the impacts of a major disturbance of aquifers.”
While these are rough estimates, they provide an order of magnitude of several decades to a few centuries to reach an absolute day zero in the capital of Chile.
Camila Álvarez, a researcher at the Center for Climate Science and Resilience CR2 and coordinator of the report, argues that water consumption during the years of mega-drought has been at the expense of exploiting groundwater sources, which is causing a sustained decline in these reserves and leading us towards a total depletion of water resources or an “absolute day zero.”
“If we consider the current water uses in the basin and a proportion of groundwater use concerning total use between 30 and 65%, the time to deplete the aquifer would be between 50 and 200 years. While these are rough estimates, they provide an order of magnitude of several decades to a few centuries to reach an absolute day zero in the capital of Chile,” explains the researcher.
In this sense, she warns that “in an adverse scenario of lower water availability and higher water use, it is likely that most of the basins in the central and northern part of the country will experience permanently high and extreme levels of water stress by the middle of this century.”
She adds, “By the end of the 21st century, conditions similar to those of the mega-drought are projected permanently, with precipitation decreases of around 30% and a lower capacity for snow storage in the Andes. This scenario implies a significant decrease in surface water availability, particularly during the summer when there is a higher water demand, representing a risk for the agricultural industry and food security.”
On the other hand, Juan Pablo Boisier, a CR2 researcher, an academic from the Department of Geophysics at the University of Chile, and a report coordinator, agreed that future water projections for Chile in climate change are negative. “In general, the scenario is adverse, in the sense that we already know that we have a climate change signal that leads to lower water availability in the central zone of Chile.”
The researcher also suggests that “we could have a condition similar to the mega-drought, but in a permanent regime, not just years, but that will be our climate, which entails a lot of impact for water stress.”
Current State of Chile
The report coordinator, Camila Álvarez, explains that “from a longer historical perspective, the trends over the last six decades indicate a significant increase in water stress levels in central Chile. This increase is first associated with the increase in water consumption and, to a lesser extent, with the decrease in surface water availability. During this period, consumptive water uses have doubled, driven mainly by the development of the agricultural and forestry industries.” In fact, according to the data studied in the report, Chile doubled its water use from 1960 to the present.
Regarding the current situation, the work indicates that “the mega-drought is directly related to the stress levels of the basins in this area. However, the increase in uses has been the predominant factor in the increase in long-term stress.”
The researcher adds that this mega-drought is partly caused by natural climate variability. Still, it overlaps and exacerbates “a trend observed over several decades towards a drier climate in central Chile, which we associate with a climate change signal.”
The Elqui, Limarí, Petorca/La Ligua, Aconcagua, Maipo, and Rapel basins, as well as those located in the coastal area of the Valparaíso and O’Higgins regions, are facing the most critical reality today. “Most of the basins between the Coquimbo and Maule regions have experienced high to extreme levels of water stress during the 2010-2020 decade. This situation is directly linked to the mega-drought and the lower water availability in this period. Still, it is substantially aggravated due to high levels of water use in these regions,” details Camila Álvarez.
Water Code and Ecological Flow
The report concludes that the ecological flow protected in Chile cannot meet the minimum environmental requirements, causing severe degradation and modification of aquatic ecosystems.
This ecological flow was included in the Water Code, which was amended in 2005. It is established that every new right to use surface water must safeguard an environmental flow, defined as the minimum amount of water that must be maintained in a surface source.
Under the current regulations, this flow maintains a maximum limit of 20% of the basins’ annual average flow, which obliges the delivery of between 80 and 100% of the surface water use rights.
According to the report, despite the progress in the regulation, this safeguard does not meet minimum environmental requirements and allows “water uses associated with extreme levels of water stress.” Furthermore, it details that “if all surface water use rights permitted by law were granted and exercised, all basins in Chile would have water stress indicators above 80%, which is associated with an extreme level of water stress.” Therefore, safeguarding the ecological flow does not meet minimum environmental requirements.
Another problem highlighted by the report is that surface and groundwater rights are assigned as fixed absolute values over time without considering long-term changes in water availability due to climate. On the other hand, the declaration of water scarcity zones exempts safeguarding ecological flows. It promotes the maintenance of water uses in times of greater availability, so its successive application promotes structural conditions of overuse and degradation of ecosystems.
It is also worth noting that the amendments to the Water Code are not retroactive. This implies that the 370 m3/s granted as Surface Water Use Rights (DAA) before 2005, corresponding to 72% of the total given to date, were not modified to include safeguarding ecological flows.
Recommendations
The report also presents recommendations to increase Chile’s water security indices, among which the following stand out:
Modify article 129 bis 1° of the Water Code that defines the ecological flow, eliminating the upper limit of 20% of the annual average flow.
In the same aspect, the report mentions the urgency of modifying Decree 71 of the Ministry of the Environment, which defines the criteria for calculating the ecological flow, to adopt a formulation that considers the minimum levels of ecosystem protection and the natural seasonal variation of the streams.
Along these lines, the report also proposes water security goals in public policy based on an objective indicator of the maximum tolerable level of water stress in the basins, considering the impacts of exceeding this level on society and ecosystems. “The objective of limiting water stress, together with goals focused on other aspects of water security (access, quality, prioritisation of uses, etc.), should guide in a cross-cutting manner the different public policy instruments, as well as political and sectoral programs,” proposes CR2 researcher Camila Álvarez.
The report “Water Security in Chile: Characterization and Future Perspectives” invites you to learn more.
