This paper presents one of the first quantitative scenario assessments for future water supply and demand in Asia to 2050. The assessment, developed by the Water Futures and Solutions (WFaS) initiative, uses the latest set of global climate change and socioeconomic scenarios and state-of-the-art global hydrological models. In Asia, water demand for irrigation, industry, and households is projected to increase substantially in the coming decades (30-40% by 2050 compared to 2010). These changes are expected to exacerbate water stress, especially in the current hotspots such as north India and Pakistan, and north China. By 2050, 20% of the land area in the Asia-Pacific region, with a population of 1.6-2 billion, is projected to experience severe water stress. We find that socioeconomic changes are the main drivers of worsening water scarcity in Asia, with climate change impacts further increasing the challenge into the 21st century. Moreover, a detailed basin-level analysis of the hydro-economic conditions of 40 Asian basins shows that although the coping capacity of all basins is expected to improve due to gross domestic product (GDP) growth, some basins continuously face severe water challenges. These basins will potentially be home to up to 1.6 billion people by mid-21st century.Plain Language Summary Home to almost 4.5 billion people, Asia has experienced unprecedented economic and population growth in recent decades. In order to sustain growing food demand and increasing standard of living, water use has been increasing rapidly in many parts of Asia. At present, water withdrawals in Asia represent 65% of the global total. This huge abstraction of water resources has resulted in many Asian regions undergoing pervasive water scarcity conditions. The imminent global changes from climate change and socioeconomic development in Asia are expected to place additional pressures on water resources in the coming decades. In such a context, it is imperative to evaluate future water scarcity conditions and identify regions at highest risk in Asia. We found that by 2050, 20% of the land area in Asia, with population exceeding 1.6-2.0 billion, is projected to experience severe water scarcity. Here, we for the first time highlight that socioeconomic changes are the main driver of worsening water scarcity in Asia, much larger than the climate change impacts.

Environmental flows (e‐flows) are powerful tools for sustaining freshwater biodiversity and ecosystem services, but their widespread implementation faces numerous social, political, and economic barriers. These barriers are amplified in water‐limited systems where strong trade‐offs exist between human water needs and freshwater ecosystem protection. We synthesize the complex, multidisciplinary challenges that exist in these systems to help identify targeted solutions to accelerate the adoption and implementation of environmental flows initiatives. We present case studies from three water‐limited systems in North America and synthesize the major barriers to implementing environmental flows. We identify four common barriers: (a) lack of authority to implement e‐flows in water governance structures, (b) fragmented water governance in transboundary water systems, (c) declining water availability and increasing variability under climate change, and (d) lack of consideration of non‐biophysical factors. We then formulate actionable recommendations for decision makers facing these barriers when working towards implementing environmental flows: (a) modify or establish a water governance framework to recognize or allow e‐flows, (b) strive for collaboration across political jurisdictions and social, economic, and environmental sectors, and (c) manage adaptively for climate change in e‐flows planning and recommendations. This article is categorized under: Water and Life > Conservation, Management, and Awareness Human Water > Water Governance Engineering Water > Planning Water

Abstract:The study of the Rio Grande/Bravo (RGB) Basin water allocation demonstrates how the United States (U.S.) and Mexico have consolidated a transboundary framework based on water sharing. However, the water supply no longer meets the ever-increasing demand for water or the expectations of different stakeholders. This paper explores opportunities for an enhanced management regime that will address past problems and better examine how to balance demands for a precious resource and environmental needs. Based on an overview of the RGB Basin context and the water allocation framework, as well as a discussion on stakeholders' ability to achieve solutions, this paper explores three key questions: (1) Does the current binational water allocation framework meet current and future human and environmental needs? (2) How can the U.S.-Mexico water allocation framework be adapted to balance social and environmental water demands so it can support and preserve the RGB Basin ecosystem? (3) What are the main opportunities to be explored for expanding the U.S.-Mexico water resources allocation framework? The U.S.-Mexico water resources framework is subject to broad interpretation and may be adapted to the circumstances taking the fullest advantage of its flexibility. Policy recommendations highlight the existing flexibility of the binational framework, the potential to move forward with an ad hoc institutional arrangement, and the creation of political will to achieve change through stakeholders recommendations.

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The Rio Grande/Bravo is an arid river basin shared by the United States and Mexico, the fifth-longest river in North America, and home to more than 10.4 million people. By crossing landscapes and political boundaries, the Rio Grande/Bravo brings together cultures, societies, ecosystems, and economies, thereby forming a complex social-ecological system. The Rio Grande/Bravo supplies water for the human activities that take place within its territory. While there have been efforts to implement environmental flows (flows necessary to sustain riparian and aquatic ecosystems and human activities), a systematic and whole-basin analysis of these efforts that conceptualizes the Rio Grande/Bravo as a single, complex social-ecological system is missing. Our objective is to address this research and policy gap and shed light on challenges, opportunities, and success stories for implementing environmental flows in the Rio Grande/Bravo. We introduce the physical characteristics of the basin and summarize the environmental flows studies already done. We also describe its water governance framework and argue it is a distributed and nested governance system across multiple political jurisdictions and spatial scales. We describe the environmental flows legal framework and argue that the authority over different aspects of environmental flows is divided across different agencies and institutions. We discuss the prioritization of agricultural use within the governance structure without significant provisions for environmental flows. We introduce success stories for implementing environmental flows that include leasing of water rights or voluntary releases for environmental flow purposes, municipal ordinances to secure water for environmental flows, nongovernmental organizations representing the environment in decision-making processes, and acquiring water rights for environmental flows, among others initiatives. We conclude that environmental flows are possible and have been implemented but their implementation has not been systematic and permanent. There is an emerging whole-basin thinking among scientists, managers, and citizens that is helping find common-ground solutions to implementing environmental flows in the Rio Grande/Bravo basin.

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Los recursos hídricos subterráneos, además de ser objeto de mecanismos de gestión cuantitativa, son la fuente principal de abastecimiento hídrico para ciertos usuarios. El acceso, el uso y el aprovechamiento de estos recursos favorecen la emergencia de tensiones entre las esferas gubernamental y social. La existencia de un decreto de veda y la falta de reconocimiento de la capacidad de participación de actores comunitarios son factores que potencializan la emergencia del conflicto. En este sentido, el liderazgo de comunidades indígenas organizadas favorece la formulación de estrategias alternativas para adaptar un longevo decreto de veda. El caso del problemático acceso por el agua en Valles Centrales (VC) de Oaxaca nos enseña que la gran oportunidad para adaptar la gestión de los recursos hídricos subterráneos reposa en las capacidades comunitarias para formular recomendaciones de política pública encaminadas a la gestión ad hoc del recurso.

Deforestation is one of the processes that most impact the functioning of terrestrial ecosystems. In Mexico and Guatemala, deforestation continues to increase at alarming rates, but there are still regions where extended areas of conserved vegetation persist, such as the Usumacinta river basin. Throughout history, various Protected Areas (PA) have been designated in this basin; however, anthropogenic activities put its natural heritage at risk. This research aimed to analyze the current status and process of forest cover loss in the region and compare it within and outside PA, as well as among different PA administrations. In 2000, 75 % of the basin's area was covered by some type of treedominated plant community. Over the following 18 years, this area was reduced by 27 %.Most of this forest loss occurred in Guatemalan territory. Although the net forest loss was higher in unprotected areas than in protected areas in Guatemala, the opposite pattern was observed in terms of the annual rate of forest loss. In the case of Mexico, forest loss was higher in unprotected areas in terms of both net forest loss and annual rates. Additionally, in both countries, PA under the administration of municipal authorities showed the lowest forest loss rates. This study showed that deforestation is an ongoing process in the Usumacinta basin with a heterogeneous spatial distribution, where PA have had different capabilities in helping conserve its forest cover. This information will be essential for binational conservation strategies aimed at preserving forest connectivity in the region.