3 Freshwater Resources Coordinating Lead Authors: Blanca E. Jiménez Cisneros (Mexico), Taikan Oki (Japan) Lead Authors: Nigel W. Arnell (UK), Gerardo Benito (Spain), J. Graham Cogley (Canada), Petra Döll (Germany), Tong Jiang (China), Shadrack S. Mwakalila (Tanzania) Contributing Authors: Thomas Fischer (Germany), Dieter Gerten (Germany), Regine Hock (Canada), Shinjiro Kanae (Japan), Xixi Lu (Singapore), Luis José Mata (Venezuela), Claudia Pahl-Wostl (Germany), Kenneth M. Strzepek (USA), Buda Su (China), B. van den Hurk (Netherlands) Review Editor: Zbigniew Kundzewicz (Poland) Volunteer Chapter Scientist: Asako Nishijima (Japan) This chapter should be cited as: Jiménez Cisneros , B.E., T. Oki, N.W. Arnell, G. Benito, J.G. Cogley, P. Döll, T. Jiang, and S.S. Mwakalila, 2014: Freshwater resources. In: Climate Change 2014: Impacts, Adaptation, and Vulnerability. Part A: Global and Sectoral Aspects. Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Field, C.B., V.R. Barros, D.J. Dokken, K.J. Mach, M.D. Mastrandrea, T.E. Bilir, M. Chatterjee, K.L. Ebi, Y.O. Estrada, R.C. Genova, B. Girma, E.S. Kissel, A.N. Levy, S. MacCracken, P.R. Mastrandrea, and L.L. White (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 229-269. 229 Table of Contents Executive Summary ............................................................................................................................................................ 232 3.1. Introduction ............................................................................................................................................................ 234 3.2. Observed Hydrological Changes Due to Climate Change ........................................................................................ 234 3.2.1. Detection and Attribution ................................................................................................................................................................. 234 3.2.2. Precipitation, Evapotranspiration, Soil Moisture, Permafrost, and Glaciers ....................................................................................... 236 3.2.3. Streamflow ....................................................................................................................................................................................... 236 3.2.4. Groundwater .................................................................................................................................................................................... 237 3.2.5. Water Quality ................................................................................................................................................................................... 237 3.2.6. Soil Erosion and Sediment Load ....................................................................................................................................................... 237 3.2.7. Extreme Hydrological Events and their Impacts ................................................................................................................................ 239 3.3. Drivers of Change for Freshwater Resources ......................................................................................................... 240 3 3.3.1. Climatic Drivers ................................................................................................................................................................................ 240 3.3.2. Non-Climatic Drivers ......................................................................................................................................................................... 240 3.4. Projected Hydrological Changes ............................................................................................................................. 241 3.4.1. Methodological Developments in Hydrological Impact Assessment ................................................................................................. 241 3.4.2. Evapotranspiration, Soil Moisture, and Permafrost ........................................................................................................................... 241 Box 3-1. Case Study: Himalayan Glaciers .................................................................................................................................... 242 3.4.3. Glaciers ............................................................................................................................................................................................. 243 3.4.4. Runoff and Streamflow ..................................................................................................................................................................... 243 3.4.5. Groundwater ..................................................................................................................................................................................... 243 3.4.6. Water Quality ................................................................................................................................................................................... 246 3.4.7. Soil Erosion and Sediment Load ....................................................................................................................................................... 246 3.4.8. Extreme Hydrological Events (Floods and Droughts) ........................................................................................................................ 247 3.5. Projected Impacts, Vulnerabilities, and Risks .......................................................................................................... 248 3.5.1. Availability of Water Resources ........................................................................................................................................................ 248 3.5.2. Water Uses ....................................................................................................................................................................................... 251 3.5.2.1. Agriculture ........................................................................................................................................................................... 251 3.5.2.2. Energy Production ................................................................................................................................................................ 252 3.5.2.3. Municipal Services ............................................................................................................................................................... 252 3.5.2.4. Freshwater Ecosystems ........................................................................................................................................................ 253 3.5.2.5. Other Uses ........................................................................................................................................................................... 253 230 Freshwater Resources Chapter 3 3.6. Adaptation and Managing Risks ............................................................................................................................. 253 3.6.1. Options ............................................................................................................................................................................................. 254 3.6.2. Dealing with Uncertainty in Future Climate Change ......................................................................................................................... 254 3.6.3. Costs of Adaptation to Climate Change ............................................................................................................................................ 256 3.6.4. Adaptation in Practice in the Water Sector ....................................................................................................................................... 256 3.7. Linkages with Other Sectors and Services .............................................................................................................. 257 3.7.1. Impacts of Adaptation in Other Sectors on Freshwater Systems ....................................................................................................... 257 3.7.2. Climate Change Mitigation and Freshwater Systems ........................................................................................................................ 257 3.7.2.1. Impact of Climate Change Mitigation on Freshwater Systems ............................................................................................. 257 3.7.2.2. Impact of Water Management on Climate Change Mitigation ............................................................................................. 258 3.8. Research and Data Gaps ......................................................................................................................................... 258 References ......................................................................................................................................................................... 259 3 Frequently Asked Questions 3.1: How will climate change affect the frequency and severity of floods and droughts? ....................................................................... 247 3.2: How will the