Chapter 4: Water | Climate Change 2022: Impacts, Adaptation and Vulnerability

This IPCC chapter assesses how climate change is affecting the water cycle, water availability, and water-related risks across human and natural systems. It is a strong source for understanding adaptation options because it explicitly identifies multiple water-management responses that recur in the literature and shows where they are already being used. The chapter highlights irrigation and water management practices, water and soil conservation measures, and other adaptation actions that improve water-use efficiency and can raise incomes and yields. It also notes that treatment and reuse of wastewater from urban residential and industrial sources may become a principal supply option under acute water scarcity, particularly where freshwater withdrawals need to be reduced. In addition, it points to the rising use of technologies that improve water-use efficiency and recover water, including drip and sprinkler irrigation, IoT-based water management, wastewater recovery technologies, desalination, and water harvesting. For a practitioner focused on resilient or regenerative water systems, the value of this source is that it places rainwater harvesting and wastewater reuse within a broader climate adaptation framework rather than treating them as isolated interventions. It also shows that these measures are not merely theoretical: the chapter synthesizes many studies and documents that these responses are already appearing across sectors, especially agriculture and urban water management. Although the chapter is not a how-to manual, it is useful for decision-makers, designers, and planners who need evidence that water recycling, recovery, and harvesting are credible adaptation pathways under climate stress. It is especially relevant for framing projects that combine rainwater capture, greywater or wastewater reuse, and efficiency upgrades as part of a wider strategy for climate resilience and reduced water demand.