A coupled human–natural system analysis of freshwater security under climate and population change

Global water availability under high-end climate change: A vulnerability based assessment

Co-development of East African regional water scenarios for 2050

Water security and food security in the Indus basin are highly interlinked and subject to severe stresses. Irrigation water demands presently already exceed what the basin can sustainably provide, but per-capita food availability remains limited. Rapid population growth and climate change are projected to further intensify pressure on the interdependencies between water and food security. The agricultural system of the Indus basin must therefore change and adapt to be able to achieve the associated Sustainable Development Goals (SDGs). The development of robust policies to guide such changes requires a thorough understanding of the synergies and trade-offs that different strategies for agricultural development may have for water and food security. In this study, we defined three contrasting trajectories for agricultural system change based on a review of scientific literature on regional agricultural developments and a stakeholder consultation workshop. We assessed the consequences of these trajectories for water and food security with a spatially explicit modeling framework for two scenarios of climatic and socio-economic change over the period 1980–2080. Our results demonstrate that agricultural system changes can ensure per capita food production in the basin remains sufficient under population growth. However, such changes require additional irrigation water resources and may strongly aggravate water stress. Conversely, a shift to sustainable water management can reduce water stress but has the consequence that basin-level food self-sufficiency may not be feasible in future. This suggests that biophysical limits likely exist that prevent agricultural system changes to ensure both sufficient food production and improve water security in the Indus basin under strong population growth. Our study concludes that agricultural system changes are an important adaptation mechanism toward achieving water and food SDGs, but must be developed alongside other strategies that can mitigate its adverse trade-offs.

Climate change is a complex and contentious public issue, but the risk-management options available to us are straightforward and have well-characterized strengths and weaknesses.

The present paper evaluates the composite risk of anthropogenic and climate change on the future water status in Jordan during the period 2030–2050. The projected water status in the country is evaluated based on the more likely population growth and climate change scenarios. The most likely figure for the population of Jordan, excluding refugees from neighboring countries, in 2040 would be ∼15 million people. Given this likely projection, though conservative, annual water needs for the domestic sector alone are expected to be between 700 and 800 million m3, with the current level of water consumption. A rise in near surface air temperature by 2 °C and a drop in total precipitation by 15%, as projected by most Global Circulation Models, would diminish renewable water resources in the mountainous region by ∼ 25–40%, being more severe as aridity increases.1. IntroductionThere is almost a consensus among earth scientists that the buildup of greenhouse gases in the atmosphere is lea...

Water security in the Global South is increasingly threatened by rapid socioeconomic changes, including urbanization, population growth, and the expansion of irrigated agriculture. These dynamics not only intensify competition for limited water resources but also amplify vulnerability to climate change impacts. The Sudano-Sahelian region, including the Sokoto Rima Basin (study area) in Nigeria, is particularly sensitive to these pressures, having experienced severe droughts in the 1970s and 1980s. This study adopts a participatory approach, leveraging stakeholder input to develop socioeconomic scenarios within the Shared Socioeconomic Pathways (SSPs) 4.5 and 8.5 frameworks. It projects future water use in the region and evaluates the combined effects of socioeconomic and climate change. While the CMIP6 GCMs agree on a wetter future climate for the region, uncertainty persists regarding the magnitude of these changes. Drivers of socioeconomic changes are better understood due to direct stakeholders involvement. Key findings indicate that by 2050, irrigated land, and population are expected to increase by 470%, and 200% respectively, relative to the reference period (1990–2004). This growth is projected to drive water demand up by 190%, outpacing the anticipated 160% increase in water availability due to climate-driven changes. The results underscore that socioeconomic changes pose a significant risk to water security and must be considered when planning climate change adaptation. Informed by stakeholder feedback, the study highlights adaptation strategies, including the adoption of water-efficient technologies, mechanized irrigation, and advanced seed technologies. Small-scale stormwater harvesting through dam construction is proposed as a viable strategy to conserve water and support municipal supplies during drought periods. This novel participatory based scenario development approach provides valuable insights into managing water resources under concurrent socioeconomic and climate challenges, with implications for policy and planning in water-scarce regions. 

The management of water resource in China has been under pressures due to rapid socioeconomic growth that escalates the demands in food, energy and domestic sectors, which rely on reliable water provision. Together with climate change, water security is expected to face greater uncertainty in the future. To support sustainable water resource management, this study established a system dynamic model to investigate the impacts of policy, socioeconomic and climate change on water security in China during 2025 to 2100. Five policy options related to carbon neutrality and water management, three socioeconomic and climate scenarios (SSP1-RCP2.6, SSP2-RCP4.5 and SSP5-RCP8.5) were considered. The results show that water demand and water resource will both be greater in the future. Under BAU, water demand will reach 514, 544 and 717 km3 while water resource will increase to 989, 992 and 1032 km3 in 2086-2100 under SSP1-RCP2.6, SSP2-RCP4.5 and SSP5-RCP8.5, respectively. Future water demand for food sector is expected to decrease slightly and then increase under SSP1-RCP2.6, while it shows continuous increase under SSP2-RCP4.5 and SSP5-RCP8.5 due to the changes of planted area, livestock and temperature. Water demand for domestic sector will decrease under three SSP-RCPs because the population will reach a peak around 2030 and then decrease with time. Water demand for energy is expected to decrease under SSP1-RCP2.6 while it will increase under other SSP-RCPs because of more energy demand under SSP2-RCP4.5 and SSP5-RCP8.5. China may face low water security pressure without policy intervention in the future especially under SSP5-RCP8.5. The analysis shows that bioenergy-oriented agriculture cannot mitigate water scarcity risks in China, while low-carbon agriculture strategies can potentially ensure water safety under carbon neutral goal. Water scarcity can be averted if we follow the development path of SSP1-RCP2.6 as well as apply interventions on water management combining with carbon neutral policies that focus on low-carbon agriculture and supplemented by low fossil energy.

Water is of vital and critical importance to ecosystems and human societies. The effects of human activities on land and water are now large and extensive. These reflect physical changes to the environment. Global change such as urbanization, population growth, socioeconomic change, evolving energy needs, and climate change have put unprecedented pressure on water resources systems. It is argued that achieving water security throughout the world is the key to sustainable development. Studies on holistic view with persistently changing dimensions is in its infancy. This study focuses on narrative review work for giving a comprehensive insight on the concept of water security, its evolution with recent environmental changes (e.g., urbanization, socioeconomic, etc.) and various implications. Finally, it presents different sustainable solutions to achieve water security. Broadly, water security evolves from ensuring reliable access of enough safe water for every person (at an affordable price where market mechanisms are involved) to lead a healthy and productive life, including that of future generations. The constraints on water availability and water quality threaten secured access to water resources for different uses. Despite recent progress in developing new strategies, practices and technologies for water resource management, their dissemination and implementation has been limited. A comprehensive sustainable approach to address water security challenges requires connecting social, economic, and environmental systems at multiple scales. This paper captures the persistently changing dimensions and new paradigms of water security providing a holistic view including a wide range of sustainable solutions to address the water challenges.

Climate change impacts on water security in global drylands

Water is of vital and critical importance to ecosystems and human societies. Issues like urbanization, population growth, socioeconomic change, evolving energy needs and climate change have put unprecedented pressure on utilization of freshwater resources. It is argued that achieving water security is the key to sustainable development. The focal point of water security evolves from ensuring reliable access of enough safe water for every person at an affordable price to lead a healthy and productive life along with maintaining the water-related ecosystem services for future generations. Although total water demand at global scale is well within available water resources, the shortages prevail at spatial and temporal scales. The constraints on water availability and water quality threaten secure access to water resources for different uses. Despite recent progress in developing new strategies, practices and technologies for water resource management, their dissemination and implementation have been limited. The chapter focuses on urban water security and their connections with practical issues dealing with real-world situations. This chapter sets the stage to understand the evolution of urban water security, its challenges and ways to achieve sustainable water management. A comprehensive sustainable approach to address water security challenges requires connecting social, economic and environmental systems at multiple scales. This chapter strives to capture the persistently changing dimensions and new paradigms of water security providing a holistic view including wide range of sustainable solutions to address the water challenges.

Integrated Water Resources Management in Practice: Better Water Management for Development , R. Lenton and M. Muller ( Editors ). Earthscan , 22883 Quicksilver Dr., Sterling, Virginia 20166-2012 . 2009 . 228 pages. $78 . ISBN 978-1-84407-650-5 . This book is a welcome addition to the literature promoting integrated water resources management (IWRM). Robert Lenton and Mike Muller make a strong case for better management of water resources using the IWRM approach, widely recognized as the most appropriate way to address a wide range of water-related development and environmental issues confronting mankind today. The presentation of recent achievements and future possibilities in equitably and sustainably managing water resources toward meeting economic and social goals and insure environmental integrity in different parts of the world may be considered a benchmark that bodes well for further progress. The book begins with an introduction to the principles and practices of IWRM, which remain poorly understood, even in the water sector and development arena. This chapter also outlines the conceptual framework used in this book, which sets it apart from other publications. This includes a focus not only on processes in IWRM (e.g., changes in policy, laws, and organizational structures) but also the ultimate outcome and impact of using this approach, rendering the book as a much needed practical guide for planners and practitioners. The four spatially structured parts of the book take the reader from the local to the basin, national, and transnational levels. Twelve of the 14 chapters present case studies in East and Southeast Asia (five chapters), Africa and Latin America (two chapters each), and in Europe, North America, and Australia (one chapter each). The case studies document how better water management guided by the IWRM approach significantly contributed to achieve a large number of development goals in different communities and countries with different socioeconomic and environmental conditions and scales. While the editors duly acknowledge the challenge of deriving overall conclusions about what works and what does not work in different settings, they are able to succinctly and convincingly distill the various strands running through the book in the Conclusion. By considering the major objectives, processes, and outcomes of good water management, the management of water at different scales, and the nature of the IWRM approach itself in the context of the various chapter studies, they conclude that in all of the cases described the basic approach that was applied recognized the following elements: (1) the unitary nature of the water resource that recognizes the interconnectedness of surface, ground, and evaporated water, (2) the physical interventions that could be adopted to manage it, (3) the limits to those physical interventions, and (4) the need for an institutional framework that brought stakeholders together in an equitable manner and gave voice to both the weak and powerful, sought to achieve a balance of interests among them, identified the environmental dimension of water management and developed organizations able to promote the overall approach. The editors further note that these elements utilized in nearly all cases presented in the book were not considered to be explicit applications of the IWRM approach but rather began before the concept was formalized (as in India, Chile, Japan, Mexico, and China) or were incidental (in South Africa and Australia). These facts help to dispel the notion that IWRM is an unrealistic, overly ambitious approach and a fixed prescription that requires the employment of all available tools in its arsenal or a magic bullet. Similarly, the focus on individual tools has tended to hamper water management and the establishment of river basin organizations as a routine first step has played only a secondary role in improving water management in many cases (in South Africa and Chile, for example) and no role in others (Japan and Denmark). These findings strengthen the editors’ argument that IWRM offers a flexible and adaptable framework within which a wide range of water and development problems in different communities and countries can be addressed. Also highlighted in the Conclusion are remaining challenges in applying IWRM in practice. They include overcoming implementation difficulties at the macro-level; finding the proper mix of formal and informal mechanisms in operations; the need for more flexible as well as community-specific and system-wide planning and management rather than blueprint packages in many developing countries; and challenges for integration arising at the interface between water, sectoral, territorial, and organizational systems, particularly governance and participation issues at the international transboundary level. The writing style is lucid and captivating and the focus on real world examples rather than theoretical constructs captivate the inquisitive mind, making it difficult to put the book down. The few typographical errors do not detract from the quality of the presentation. Three relatively minor technical problems – the use of the same gray tones for different categories of water stress indicators in Figure 1.1 instead of using a color scheme, the poor print quality of this world map (all other figures in the book are excellent), and the weak binding I noticed on my paperback copy – should not detract from the intrinsic value of this well conceived and meticulously researched book. As a geographer interested in Third World water resources management and water-related health problems I enjoyed reading the broadly based case studies presented in this much needed book. Planners, water managers, researchers, and students will want to have a copy on their shelves for reference, guidance, and inspiration. Helmut Kloos Department of Epidemiology and Biostatistics University of California San Francisco, California 94134-0560 E-mail: helmutk@comcast.net The Sustainable Management of Groundwater in Canada , The Expert Panel on Groundwater . Council of Canadian Academies , 180 Elgin St., Ste. 1401, Ottawa, Ontario, Canada K2P 2K3 . 2009 . 253 pages . ISBN 978-1-926558-09-7 . I enthusiastically agreed to review this book, The Sustainable Management of Groundwater in Canada (Groundwater) penned by the Expert Panel on Groundwater (Panel) not only because I have a great interest in sustainability issues but also because I had heard much in the popular press about the Athabasca Oil Sands project and I hoped the Panel would discuss energy production and sustainable use of water – I was not disappointed on either count. I do not want to mislead the reader though –Groundwater covers a wide range of topics from governance to flow modeling to markets and case studies. Although Groundwater was written explicitly for or from a Canadian perspective, many if not all of the topics are applicable to work in other countries. Many of the authors that served on the Panel are instantly recognizable names with groundwater and hydrology experience garnered from across the globe (interestingly, but not surprisingly, many of these world renowned authors work in Canada); this breadth and depth of expertise helps to make Groundwater a relatively easy to read book especially given the complex nature of groundwater and sustainability. There are too many topics to discuss in detail in this review. Still, to give the reader a sense of this book, some of the salient topics are reviewed here. The Panel identified five sustainability goals to include protection of groundwater from depletion and contamination, protection of ecosystem viability, achievement of economic and social well being and application of good governance; these individual sustainability goals are envisioned as equal members in the schematic put forth by the Panel. This reader agrees that this pentad of sustainability goals should be implemented in future projects although if history teaches us anything, in practice, these goals might not enjoy equal strength or standing; the Panel offers case studies that illustrate the importance of the implementation of (or, sadly, as the case may be, lack of) sustainability goals. Part of the appeal of Groundwater is the ability of the Panel to explain abstruse concepts by the judicious use of footnotes and many well written topic-boxes. One such footnote on page 17 helps exemplify the pedagogical tenor of Groundwater and (a portion of this particular footnote) is well worth repeating here: “The precautionary principle seeks to encourage those undertaking projects to consider and address harm to the public or the environment even if the scientific consensus that harm will occur is unclear.” Unfortunately, it seems from some of the case studies discussed here, all too often, the precautionary principle has not been applied in many cases. An example of topic-box discussions is given on page 113, where the Panel expands on topics such as the Tragedy of the Commons and water. I cannot help but wonder if present day appropriation schemata, such as the doctrine of prior appropriation, riparian rights, correlative rights, rule of capture, etc., have helped to perpetuate the tragedy. Hopefully, some day soon, the Tragedy of the Commons will be relegated to a footnote in history. The Panel discusses many case studies to help illustrate the effects of climate change (Prairie Groundwater), population growth (Denver Basin), and energy production (Athabasca Oil Sands) on sustainable use of water. Groundwater incites some mental rumination (and this is why I am excited by this type of book) – each of these case studies could also be seen to show how climate change, population growth, and energy production also affect another timely topic – food production and economic security. It should be noted that the Panel briefly discusses bio-fuel production generally – presumably because this topic and technology is in an almost mercurial state of flux. However, probably one of the most important topics discussed in Groundwater concerns the use of “... economic instruments such as water prices, abstraction fees, and tradable permits...” to help manage water. This of course could be seen to be a point of contention in places where present day appropriation rules govern water allocations. Given the stressors that affect water such as climate change, population growth, and food and energy security, economic instruments might offer an attractive means to equitably manage water resources (to be fair the significance of these stressors might not have been recognized in earlier times when various appropriation rules were enacted). The Panel notes numerical modeling simulation studies that “...show a significant improvement in the efficiency of water allocation (relative to current allocations) as a result of water trades.” In the face of these changes in climate and population, it may be time to heed these tocsins presented in the various case studies and perhaps consider a retooling of management and regulations schema. In sum, The Sustainable Management of Groundwater in Canada, is an easy to read book written by an expert panel of world renowned water experts. The topics are fresh and timely and applicable both in Canada as well as other parts of the world. I am glad that I read the book and would suggest that it be included on a must-read list to colleagues. Kevin Jeffrey Spelts Twin Platte Natural Resources District, 302 S. Oak St., North Platte, Nebraska 69101 Fluvial Hydraulics , L. Dingman . Oxford University Press , 198 Madison Ave., New York, New York 10016 . 2009 . 559 pages . ISBN 978-0-19-517286-7 . I became familiar with Professor Dingman’s work when I used his Fluvial Hydrology (Dingman, 1984, now out of print) for my graduate work in channel morphology and sediment transport. Fluvial Hydraulics builds upon the geomorphology and fluvial hydraulics presented in Fluvial Hydrology, but Dingman’s new book includes more information on basic-fluid mechanics and a more extensive discussion of the characteristics of natural rivers. Dingman’s preface to Fluvial Hydraulics states that “The overall goal of this book is to develop a sound qualitative and quantitative understanding of the physics of natural river flows for practitioners and students.” That goal is most certainly met. Fluvial-hydraulics concepts, from basic hydraulic relationships to complex phenomena such as turbulence and hydraulic jumps, are clearly presented. The equation derivations are logical and fairly easy to understand. The figures and photographs are clear and complement understanding of the text. Examples and additional derivations are presented in boxes for the reader who is interested in a deeper understanding of the material. Dingman begins with an Introduction that describes volumes of water in the components of the hydrologic cycle and in the world’s largest rivers. The Introduction also includes a fascinating history of fluvial hydraulics and personalities that advanced the science. Chapters 2, 3, and 4 provide a foundation for the study of open-channel flow. In Chapter 2, Dingman discusses the morphologic and hydrologic characteristics of natural streams; in Chapter 3, he describes water’s atomic and molecular structure and other properties. Then, in Chapter 4, Dingman introduces the basic equations for fluid properties and hydraulic variables, including relationships based on the conservation of mass, momentum, and energy, and equations based on diffusion and force/balance relationships. Equations based on dimensional analysis and empirical and heuristic relations also are described. Chapters 5, 6, and 7 present relationships between velocity and flow resistance, the Prandtl-von Karman vertical-velocity profile, the Chezy, Darcy-Weisbach, and Manning’s equations, and magnitudes of driving and resisting forces in natural streams. The next two chapters discuss momentum and energy principles, equations for gradually-varied flow, and methods for calculating water-surface profiles. In Chapter 10, Dingman describes steady, rapidly-varied flow, including analysis of hydraulics at abrupt transitions and structures for discharge measurement. In Chapter 11, he discusses unsteady flow, including an excellent description of waves and prediction of wave depths and speed of travel. In Chapter 12, he discusses sediment entrainment and transport, including sediment-transport measurement, factors that dictate the shape of alluvial channel cross sections, and flow competence. Appendix A presents thorough discussions on dimensions, units, and numerical precision. In lieu of problems or exercises, Dingman provides online spreadsheets for flow databases, synthetic channel hydraulics, and water-surface profile computations. These spreadsheets are described in Appendices B, C, and D. I was unable to reach the website at the URL included in the text, but found the spreadsheets at this URL by searching the publisher’s website: http://www.oup.com/us/companion.websites/9780195172867/?view=usa. I was unable to find the links to other fluvial geomorphologic websites or discussion pages noted in the introduction. The book will be useful for an undergraduate-level or graduate-level class in channel hydraulics and morphology, for students with an understanding of basic calculus and university-level physics. For civil engineers, the book is a valuable companion to classic open-channel texts because it includes extensive discussions and applications focused on natural streams. For researchers, practitioners, and students in the natural-resources sciences, the book provides clear and complete discussions of open-channel flow that do not require a theoretical background in fluid mechanics to understand. This book will spend more time on my desk than on my shelf; I will refer to it often. Katherine J. Chase, PE 541 Diehl Dr. Helena, Montana 59601 The World’s Water: 2008-2009, The Biennial Report on Freshwater Resources , P.H. Gleick with H. Cooley , M.J. Cohen , M. Morikawa , J. Morrison , and M. Palaniappan . Island Press , 1718 Connecticut Ave. NW, Ste. 300, Washington, D.C. 20009 . 2008 . 402 pages. $35 . ISBN 978-1-59726-505-8 . The First Biennial Report on Freshwater Resources for the world by Peter H. Gleick was issued in 1998. The Sixth Biennial Report by Peter H. Gleick and his associates is the latest version and covers the period 2008-2009. The series continues to be an invaluable collection of all kinds of water-related material, ranging from concise stand-alone chapters on important topics to numerous sections of data that have been updated as much as possible given the mix of reporting countries. A sampling of some of the six discussion chapters that are at the beginning of the book of 402 pages should provide the reader a good sense of the nature of the material. The first chapter by M. Palaniappan and P. H. Gleick on “Peak Water” provides an interesting discussion of the similarities and differences between oil and water. The importance of ocean water desalination is that the amount is unlimited, but the problem is how much we are willing to pay for it. In areas where water is really scarce, such as selected islands in the Caribbean and certain parts of the Persian Gulf, desalination is already becoming an “economically competitive alternative.” Chapter 2 on “Business Reporting on Water” by M. Morikawa, J. Morrison, and P. H. Gleick provides a useful accounting of corporate reporting of non-financial environmental information in annual reports that started in the 1970s. These non-financial reports have grown from fewer than 50 in 1992 to over 1,900 in 2005 and 2,470 by 2007. As expected, water management and use reporting by major corporations vary from industry to industry. In addition, and regrettably, most corporations rarely report on water recycling and reuse. The next chapter by H. Cooley deals with water management in a changing climate. A sampling of some of the water resource issues associated with climate change include the following: (1) climate change will affect the quantity and timing of surface runoff, (2) groundwater is less understood than surface water and sea level rise could result in greater saltwater intrusion in coastal aquifers, and (3) agriculture accounts for 70-80% of global water use and lawns in hot, dry areas can account for 70% of total residential water use. Even in developed countries, water infrastructure that was designed and operated on historic water conditions may become a problem in the future. In 2002, 1.1 billion people did not have access to improved water supply and 2.6 billion did not have access to improved sanitation. Of particular interest is the section from pages 151-193 by P. H. Gleick pertaining to the chronology of water conflicts from Noah’s flood of about 5,000 years ago to fights between animal herders and farmers in Burkina Faso, Ghana, and Cote D’Ivoire in 2007 in the Sahel region of West Africa just south of the Sahara Desert. a description of the of the the and the It is clearly a valuable on the world history of water conflicts that are not in number and of this book is the of that on pages A sampling of these data include information on water and use by data on access to water and updated on in Africa and the information on in five years of from water-related and data on the of water in selected countries and In this book is as an excellent of information on the world’s It is well and includes an extensive on a of water-related It is a for interested in the water resource Robert M. Water Resources New A of the of 2008 , ( ). University of Press , . . pages. . ISBN . 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Africa is considered to be the second driest continent in the world after Australia. Sub-Saharan Africa (SSA) is the whole of Africa except North Africa; SSA covers around 80% of Africa’s total land area with a population of around 0.9 billion people. The continued population growth poses a challenge to systems that supply services in SSA; for example, in 1950, less than 200 million people lived in Sub-Saharan Africa, but in 2016 the population in SSA has increased to around 1 billion. Since the beginning of the 21st century, there has been a rising sense of urgency about the need to address migration; movement of refugees and their displacement (Cross et al., 2006). There are many factors that influence the movement of people. This thesis examines some of these factors in depth to understand the tendency for migration both to urban from rural and from rural to urban – the latter being more important. Presently, 14 African countries (including 9 from SSA) are experiencing water stress, and it is predicted that the number of water stressed countries in SSA will increase to 25 countries by the year 2025 (Mejia et al., 2012; UN, 2008). SSA experiences rainfall fluctuations and rising temperatures that have been impacting the agricultural production over time. It is predicted that SSA may experience extreme rainfall events and such extreme precipitation may become more frequent and intense over time. Local rural water availability conditions may also face more challenges; for example, Nigeria water supply systems have failed to cope with the rapid population growth over time. In 1991, 79% (25 million) of Nigerian people living in urban areas had access to clean water, yet 17 years later it has fallen to 75%, but now 55 million people have access to fresh water. The literature reviewed showed a number of gaps in research with regards to water security. Essentially, this thesis investigates how water security, climate change and population growth are related to the people movement in and around SSA. This study uses quantitative type univariate and multivariate time series methodologies to investigate the links among the abovementioned variables. The main research aim of this major study as stated led to the examination, study and analysis of long term time series data concerning rainfall, temperature, populations; including their relationships to rural-urban and urban to rural migration time series data. The study developed univariate and multivariate time series models that are appropriate for trend studies, and prediction of the changes that may occur to the climatic and people movement variables in the future. The study identified associations and correlations between climatic and people movement variables. The findings of this study indicate that rainfall and temperature variabilities do indeed impact the movement of people in SSA in Somalia, Ethiopia and Democratic Republic of Congo in particular. The results of the time series analyses suggest that rainfall has a greater impact on rural-urban migration in Somalia, Ethiopia and Democratic Republic of Congo compared to that of the temperature; although a combined effect is also noted. The people movement in these countries responded to the unit shocks in rainfall or temperature. More importantly, the study notes that number of people leaving from rural areas outnumber those relocating to rural areas. This means that migration in selected countries and in SSA in general has net flows towards the cities. Due to limitations of the migration data availability, author used vital statistical method to indirectly measure net migration in selected countries. The study provides an essential breakthrough of the area of the climate change impact on rural urban migration in SSA. The findings can aid different levels of decision making authorities, research and educational institutions in the regions as well as regional and international organization in terms of what may be done to stem the flow away from rural areas. Hence, there is a need for more site specific research projects to further examine interactions and associations between climate change and human migration within SSA and member counties. Higher level studies in the future should seek funding from agencies to collect primary data from relevant government departments as well as climate related research institutions in SSA.

Abstract. Many regions in Chile experienced an unprecedented drought from 2010 to 2022, driven by climate change and natural variability. This so-called megadrought led to severe water scarcity, causing conflicts and exposing issues in Chilean water regulations. Water-intensive agriculture in areas with limited water availability has worsened these problems, raising questions about the relative contributions of water extraction and climate to high water stress levels. In this study, we evaluate past and present-day water stress conditions in Chile, as well as future projections under various climate and socio-economic scenarios. To this end, novel datasets of water availability, land use and water use were developed, extending back to mid-20th century. Using these datasets, we calculated the Water Stress Index (WSI) for all major basins in the country and assessed the impact of increasing water use and climate change on water stress over different time periods. Results show that most basins in semi-arid regions experienced high to extreme water stress (WSI >40 % and WSI >70 %, respectively) during the megadrought, mainly due to reduced water availability, but worsened by high water demand. In a long-term perspective, water stress in central Chile has steadily increased, primarily driven by rising water consumption and to a lesser extent by changes in water availability, leading to sustained (1990–2020 average) high water stress levels in several basins from Santiago northward. Under an adverse climate scenario (SSP3-7.0), megadrought-like conditions could become permanent by the end of the 21st century, with a projected 30 % drop in precipitation, resulting in high to extreme water stress in most basins in central Chile. We argue that using the WSI to assess one of the several aspects of water security offers a valuable strategy for adaptation plans. If public policy agrees on establishing quantifiable water security goals based on metrics like the WSI, different pathways of water use combined with alternative water sources can be evaluated to achieve them.

Water is an essential resource for social and economic development. The availability of this resource is constantly threatened by the rapid increase in its demand. This research assesses current (2010–2016), short- (2017–2040), middle- (2041–2070), and long-term (2071–2099) levels of water security considering socio-economic and climate change scenarios using the Water Evaluation and Planning System (WEAP) in Vilcanota-Urubamba (VUB) catchment. The streamflow data of the Pisac hydrometric station were used to calibrate (1987–2006) and validate (2007–2016) the WEAP Model applied to the VUB region. The Nash Sutcliffe efficiency values were 0.60 and 0.84 for calibration and validation, respectively. Different scenarios were generated for socio-economic factors (population growth and increased irrigation efficiency) and the impact of climate change to evaluate their effect on the current water supply system. The results reveal that water availability is much higher than the current demand in the VUB for the period (2010–2016). For short-, middle- and long term, two scenarios were considered, “Scenario 1” (RCP 4.5) and “Scenario 2” (RCP 8.5). Climate change scenarios show that water availability will increase. However, this increase will not cover the future demands in all the sub-basins because water availability is not evenly distributed in all of the VUB. In both scenarios, an unmet demand was detected from 2050. For the period 2071–2099, an unmet demand of 477 hm3/year for “Scenario 1” and 446 hm3/year for “Scenario 2” were estimated. Because population and agricultural demands are the highest, the effects of reducing the growth rate and improving the irrigation structure were simulated. Therefore, two more scenarios were generated “Scenario 3” (RCP 4.5 with management) and “Scenario 4” (RCP 8.5 with management). This socio-economic management proved to be effective in reducing the unmet demand up to 50% in all sub-basins for the period 2071–2099.

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