Fresh Water

Chapter 7

Fresh Water
Coordinating Lead Authors: Charles J. Vorosmarty, Christian Leveque, Carmen Revenga ´ ˆ ¨ ¨ Lead Authors: Robert Bos, Chris Caudill, John Chilton, Ellen M. Douglas, Michel Meybeck, Daniel Prager Contributing Authors: Patricia Balvanera, Sabrina Barker, Manuel Maas, Christer Nilsson, Taikan Oki, Cathy A. Reidy Review Editors: Frank Rijsberman, Robert Costanza, PedroJacobi

Main Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167 7.1 Introduction to Fresh Water as a Provisioning Service . . . . . . . . . . . 168
7.1.1 7.1.2 Fresh Water in the MA Context Setting the Stage

7.2

Distribution, Magnitude, and Trends in the Provision of Fresh Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . 170
7.2.1 7.2.2 7.2.3 7.2.4 7.2.5 Available Water Supplies for Humans Water Use The Notion of Water Scarcity Environmental Flows for Ecosystems Water Quality

7.3

Drivers of Change in the Provision of Fresh Water . . . . . . . . . . . . . . 181
7.3.1 7.3.2 7.3.3 7.3.4 7.3.5 7.3.6 Population Growth and Development Managed Water Supplies Land Use and Land CoverChange Climate Change and Variability Urbanization Industrial Development

7.4

Consequences for Human Well-being of Changes in the Provision of Fresh Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190
7.4.1 7.4.2 7.4.3 7.4.4 7.4.5 Freshwater Provision: Benefits and Investment Requirements Consequences of Water Scarcity The Cost and Pricing of WaterDelivery Consequences of Too Much Water: Floods Consequences of Poor Water Quality on Human Health

7.5

Trade-offs in the Contemporary Use of Freshwater Resources . . . . . . 197

REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201

165

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7.1 7.2 7.3 7.4 7.5

Ecosystems and Human Well-being: Current State and Trends
7.127.13 7.14 7.15 Time Series of Renewable Water Supply across the Global Landmass since 1920 Proportion of Population with Improved Drinking Water Supply, 2002* Proportion of Population with Improved Sanitation Coverage, 2002* Trade-off Analysis, Depicting Major Interventions and Consequences on Condition of Ecosystems and Development Goals

Operational Definitions of Key Terms on Fresh WaterMinisterial Declaration from the 2nd World Water Forum Uncertainties in Estimates of Contemporary Freshwater Services, Use, and Scarcity Virtual Water Content Associated with African Food Supply Defining Improved Water Supply and Sanitation

FIGURES
7.1 Global Renewable Water Supply as River Discharge and Populations Dependent on Accessible Runoff at Point of Origin* Cumulative Distribution ofPopulation with Respect to Freshwater Services, 1995–2000 Contemporary Geography of Non-sustainable Withdrawals for Irrigation* Managing for Environmental Flows: Contrasts among Natural, Reservoir-affected, and Reconstituted River Discharge Regimes Contrast between Mid-1990s and Pre-disturbance Transports of Total Nitrogen through Inland Aquatic Systems Resulting from Anthropogenic Acceleration of ThisNutrient Cycle* Global Summary of Inorganic Nitrogen Transport by Contemporary Rivers Ranking of Globally Significant Water Quality Issues Affecting the Provision of Freshwater Services for Water Resource End Uses Time Series of Intercepted Continental Runoff and Large Reservoir Storage, 1900–2000 Net Inter-regional Trade in Major Crops Expressed as Embodied or ‘‘Virtual’’ Water Expended inProduction of These Agricultural Commodities, 1995–99 Percentage of Cropland Area by River Basin* Percentage Urban and Industrial Land Use by River Basin* 7.1 7.2

TABLES
Major Storages Associated with the Contemporary Global Water System Estimates of Renewable Water Supply, Access to Renewable Supplies, and Population Served by the Provision of Freshwater Services, Year 2000 Condition Freshwater...