Climate Adaptation Needs to Reduce Water Scarcity Vulnerability in the Tagus River Basin

Abstract

In southern Europe, climate change is expected to aggravate water scarcity conditions and challenge current water management practices. The present paper evaluates the impacts of climate change in the highly regulated Tagus River basin and assesses various adaptation options, quantifying the effort needed to maintain the ability to sustain current water uses. A water management and allocation model covering surface and groundwater resources is used to evaluate available and renewable water resources for different climate scenarios. Additionally, the Water Exploitation Index Plus (WEI+) and water supply reliability criteria are used to quantify water scarcity and the ability to satisfy water demands, respectively. The results show that climate change will significantly change the stream flow regime and reduce water availability in the Tagus River basin, but the existing reservoir infrastructure will alleviate some of these impacts, especially in the dry half-year. Until the end of the century, water scarcity levels, measured by annual WEI+, are expected to increase in the Tagus River basin from 0.46 to 0.52 or 0.62, respectively under two Representative Concentration Pathways (RCP 4.5 or RCP 8.5). The benefits of streamflow regulation vary with the hydrological regimen, the current degree of water use and the role of groundwater resources to meet demand. The benefits of streamflow regulation are also dependent on the environmental flow requirements that will be adopted in the future. A reduction of water consumption for irrigation by 25% to 40% will significantly improve the Tagus River system performance and maintain the current scarcity situation in the future, under the expected scenarios of climate change.

Framework for Assessing Collective Irrigation Systems Resilience to Climate Change—The Maiorga Case Study

“…The results presented in [32] show that climate change will significantly change the stream flow regime and reduce water availability in a Portuguese river basin, but the existing reservoir infrastructure will alleviate some of these impacts, especially in the dry half-year. According to [29,32], in southern Portugal, the water supply-demand unbalance may lead to a decrease in irrigated areas, changes in cropping patterns and/or a decrease in production due to impacts of water deficit. In addition to these changes, it is expected that irrigation water productivity (ration yield and irrigation water, kg m −3 ) will decrease, even if crop productivity remains unchanged [27][28][29][30].…”

“…Regarding the latter, the projected climate change impacts include decreases in runoff and streamflow-due to progressive shifts in seasonal rainfall distribution and in intensity-and increase in the frequency and severity of extreme climatic events (e.g., droughts and floods) [26][27][28][29][30][31]. The results presented in [32] show that climate change will significantly change the stream flow regime and reduce water availability in a Portuguese river basin, but the existing reservoir infrastructure will alleviate some of these impacts, especially in the dry half-year. According to [29,32], in southern Portugal, the water supply-demand unbalance may lead to a decrease in irrigated areas, changes in cropping patterns and/or a decrease in production due to impacts of water deficit.…”

“…Over 80% of the agricultural production in the Mediterranean region comes from irrigated areas, which is why it is essential to optimize water productivity [33,34] to continue satisfying the future demand for food in a context of increasing water scarcity. Measures to this end must be applied: (i) at demand level (e.g., improvements in the efficiency of water use, water prices, and changes to more resilient crops) and; (ii) at the supply level (e.g., rehabilitation of water conveyance and distribution infrastructures to reduce water losses from the water source to the farm, and the improvement of on-farm water application [9,21,32,35]).…”

“…Thus, it is important to proceed with the CIS rehabilitation, where the original design criteria must be updated aiming at considering climate change impacts since infrastructures with a long-life span are included [37]. Rehabilitation may involve structural changes, which requires a large capital investment [32]. However, the investment should be proportionate to the increase in climate resilience associated to different rehabilitation alternatives.…”

Influential Spanish Politicians’ Discourse of Climate Change on Twitter: A Corpus-Assisted Discourse Study

“…It can investigate the stories we live by—mental models that influence behaviour and lie at the heart of the ecological challenges we are facing. (Stibbe, 2015 : 1–2)…”