This book highlights the likely impacts of climate change in terms of global and national water securities, how different countries are attempting to address these complex problems and to what extent they are likely to succeed.  A major global concern at present, especially after the social and economic havoc that has been caused by COVID-19 in only one year, is how we can return to earlier levels of economic development patterns and then further improve the process so that sustainable development goals are reached to the extent possible by 2030, in both developed and developing countries. Mankind is now facing two existential problems over the next several decades. These are climate change and whether the world will have access to enough water to meet all its food, energy, environment and health needs. Much of expected climate change impacts can be seen through the lens of extreme hydrological events, like droughts, floods and other extreme hydrometeorological events. Chapter 7 is available open access under a Creative Commons Attribution 4.0 International License via link.springer.com.Chapter 12 is available open access under a Creative Commons Attribution-NonCommercial 4.0 International License via link.springer.com.