Ebb and Flow: Volume 1. Water, Migration, and Development

Migration shapes the lives of those who move and transforms the geographies and economies of their points of departure and destinations alike. The water sector, and the availability of water itself, implicitly and explicitly shape migration flows. Ebb and Flow: Volume 1. Water, Migration, and Development presents new global evidence to advance our understanding of how fluctuations in water availability, as induced by rainfall shocks, influence internal migration, and hence regional development. It finds that cumulative water deficits result in five times as much migration as water excess does. But there are important nuances in why and when these events lead to migration. Where there is extreme poverty and migration is costly, water deficits are more likely to trap people than induce them to migrate. Water shocks can also influence who migrates. Workers leaving regions because of water deficits are often less advantaged than typical migrants and bring with them lower skills, raising important implications for the migrants themselves and receiving regions. Cities are the destination of most internal migrants, but even here, water scarcity can haunt them. Water shortages in urban areas, which lead to so-called day zero events, can significantly slow urban growth and compound the vulnerability of migrants. No single policy can be completely effective at protecting people and their assets from water shocks. Instead, the report puts forth a menu of overlapping and complementary policy options that target both people and places to improve livelihoods and turn water-induced crises into opportunities for growth. A key message is that policies that focus on reducing the impacts of water shocks must be complemented by strategies that broaden opportunities and build the longterm resilience of communities. Doing so will give individuals more agency to determine the best outcome for themselves and to thrive wherever they may choose to locate.

Front Cover -- Contents -- Acknowledgments -- Abbreviations -- Executive Summary -- Focus of the Report -- Taking a Global, Long-Run Perspective -- Stay or Go: Why and in What Context Do Water Shocks Induce Migration? -- Water, Migration, and Human Capital Spillovers: Who Are the Typical Migrants and What Human Capital Do They Carry with Them? -- The Cost of Day Zero Events: What Are the Development Implications for Shocks in the City? -- Going with the Flow: The Policy Challenge -- References -- Chapter One Transitions and Transformations -- Introduction -- Focus of the Report -- Climate Change and the Increasing Variability of Rainfall -- Learning about Water's Role in Global Migration from Half a Billion Individual Records -- Social Dimensions of Migration -- Structure of the Report -- References -- Spotlight Inequality, Social Cohesion, and the COVID-19 Public Health Crisis at the Nexus of Water and Migration -- Chapter Two Stay or Go? -- Key Highlights -- Introduction -- Should I Stay or Should I Go? Estimating the Impacts of Water Shocks on Migration Decisions -- Does Buffering Rural Income from Rainfall Shocks Influence Migration? -- Irrigation Costs and Forest Loss -- Water as a Conduit for Development -- Notes -- References -- Chapter Three Water, Migration, and Human Capital Spillovers -- Key Highlights -- Introduction: The Human Capital Channel -- From Temporal to Spatial Spillovers -- Water Shocks, Distress Migration, and Workers' Skills -- Productivity, Growth, and Welfare -- Adaptation Strategies, Adjustment Channels, and Regional Specificities -- Implications for Development Policy -- Note -- References -- Chapter Four The Cost of Day Zero Events -- Key Highlights -- A Historical Perspective on Droughts and Cities -- Learn from the Past or Be Doomed to Repeat It -- The Importance of Water for Growth.

Quantifying the Cost of Day Zero-Like Events -- The Way Forward -- Notes -- References -- Chapter Five Going with the Flow -- The Policy Challenge -- Policy Options at the Origin -- Policy Options at the Destination -- Weighing Policy Options -- Annex 5A Projected Changes in Annual Rainfall in Africa -- Notes -- References -- Boxes -- Box 1.1: Water and the Urbanizing Force of Development -- Box 1.2: Is Water a Locational Fundamental? -- Box 1.3: COVID-19 (Coronovirus) Fallout -- Box 1.4: Exploring Water Scarcity through Water Shocks -- Box 1.5: Harnessing the Power of Machine Learning -- Box 1.6: Social Cleavages Run Deep -- Box 2.1: Using Disaggregated Global Data to Illuminate Water and Migration Links -- Box 2.2: Choosing Not to Migrate -- Box 2.3: Measuring the Buffering Effect of Gray and Green Infrastructure -- Box 2.4: Water Shocks and Declining Wetlands -- Box 2.5: Irrigation Costs and Forest Loss -- Box 3.1: Examining Determinants of Migrants' Human Capital through Census Data -- Box 3.2: Rainfall, Education, and Regional Migration-Evidence from Cross-Sectional Data -- Box 3.3: Drought and Rural-Urban Migration: Impacts of Cumulative Rainfall Shocks -- Box 4.1: The Resilience of Urban Water Systems -- Box 4.2: Measuring the Impacts of Water Deficits on Economic Activity in Cities -- Box 5.1: Analytical Approaches Help Decision-Makers Confront Large Uncertainties -- Box 5.2: New Ideas to Thwart the Next Urban Water Crisis -- Box 5.3: Place-Based Policies and Risk Management -- Figures -- Figure ES.1: This Report Takes a Global Perspective to Answer Three Questions -- Figure ES.2: The Importance of Various Characteristics in Explaining Migration -- Figure ES.3: Impact of Rainfall Shocks on Out-Migration Rates, by Income -- Figure ES.4: Rainfall and Migrants' Education.

Figure ES.5: Impact of Rainfall Shocks on City Growth Rates at Urban Water Points -- Figure ES.6: Water Shapes Migration and Development -- Figure ES.7: Policies and Investments to Sustain Prosperity -- Figure 1.1: The Report Takes a Global Perspective to Address Three Questions -- Figure 1.2: The Importance of Water Shocks in Explaining Migration -- Figure 2.1: Main Results at a Glance: Channels through Which Rainfall Deficits Affect Migration -- Figure 2.2: Impact of Rainfall Shocks on Out-Migration Rates, by Agricultural Dependence and Income Distribution -- Figure 2.3: Impact of Rainfall Shocks on Out-Migration Rates, by Gray (Irrigation) and Green (Forest) Infrastructure -- Figure 3.1: Rainfall and Migrants' Education -- Figure 3.2: Migrant Skills and the Presence of Large Cities -- Figure 4.1: Impact of Water Supply Shocks on City Growth Rates -- Figure 4.2: Impact of Water Supply Shocks on Urban Luminosity Growth Rate, by Climate -- Figure 4.3: Impact of Water Supply Shocks on Urban Luminosity Growth Rate, by City Population Size -- Figure 4.4: Impact of Weather at Nonsurface Urban Water Points on Urban Luminosity Growth Rate, Placebo Test -- Figure 4.5: Comparison of Water-Intensive and Water-Scarce Economies, Nonagricultural -- Figure 5.1: Policy Approaches at the Source and Destination -- Figure 5.2: Share of Regions in North Africa and G5 Sahel Countries That Experienced Different Types of Conflict Events, by the Presence of Irrigation -- Figure 5.3: Policies and Investments to Sustain Prosperity -- Figure 5A.1.1: Projected Changes in Annual Rainfall in Africa -- Maps -- Map B1.2.1: Clustering of Cities along Major River Basins -- Map B3.2.1: Regions Used in the Cross-Sectional Analysis -- Map B3.3.1: The Subregions of Brazil, Indonesia, and Mexico Explored Using Census Data.

Map 4.1: Location of Cities Experiencing Deep Three-Plus Years of Water Deficits, 1992-2013 -- Tables -- Table 4.1: Drought Events in Major Urban Water Supply Systems -- Table 4.2: Cities Facing Largest Three-Year Water Deficits -- Table B5.3.1: Typology of Options for Risk Management.