The hydrological transition Water is the primary vector through which the socio-economic impacts of climate change are, and will be, felt. Water has been increasingly recognized over the past decade as a central element of climate change adaptation. The Intergovernmental Panel on Climate Change (IPCC) states with very high confidence that the most effective actions to reduce vulnerability in the short-term are to implement “basic public health measures such as the provision of clean water and sanitation [...] and alleviate poverty”. As such, climate change adaptation should occur through a ‘hydrological transition’ that strengthens social and environmental resilience. The hydrological transition must address the water, sanitation and hygiene sphere holistically, including eliminating inequalities in access to water and sanitation and associated vulnerabilities. It should also address restoring the good status of aquatic ecosystems and rigorous hydrological, territorial and urban planning, as well as identifying, preventing and minimising the main risks of desertification, drought and flooding arising from climate change and the impacts of rising sea levels. The hydrological transition speaks to the need to reintegrate the human rights to safe drinking water and sanitation into many areas of climate action, and of water and sanitation provision. These areas are discussed under four main areas of conversation in climate action: A. Adaptation C. Finance B. Mitigation D. Cooperation 2