Climate changes have a significant impact on water resources and cause for instance increased frequencies and greater extremes of floods and droughts in addition to temperature increases. Averages of hydrometeorological parameters are changing and there is variation in the stability and onsets of rainy seasons. The impacts of changes in water resources in time, space and quality can be very severe and can be experienced across all water bodies and water dependent natural and human systems. Systems as diverse as forests and aquatic ecosystems are undergoing changes.
Globally there are major differences in the ability of people, organisations and systems to face and manage adverse conditions, emergencies or disasters. Under unfavourable conditions and where the coping capacity of people, organisations and systems is low, the vulnerability is high.
Policy decisions are needed to prioritise alleviation and adaptation measures including disaster risk management. Such policy decisions will have vulnerability assessments as an important decision parameter. Vulnerability assessments concern both human and natural systems. Vulnerability assessments build on evaluations of exposure and sensitivity which will combine to yield potential impacts.
Assessing the potential impacts together with adaptive capacity will result in an evaluation of the vulnerability. Alleviation or adaptation strategies therefore involve the identification of sectors/systems/areas vulnerable to change and an examination of the scope to increase the coping capacity of these systems – their resilience - which will reduce the level of vulnerability once implemented. Coping capacity can rationally be expanded by applying the approaches of IWRM. Prioritisation will take into account the consequences of system failure or reduction, and the potential for improvement through planned adaptation.
An illustrative assessment system is the Climate Vulnerability Index (CVI) which is based on a series of variables clustered under headings of; Resource (water resources characteristics), Access (to water and sanitation), Capacity (social, institutional and economic indicators), Use (the value of water in its uses), Environment (habitats, population and livestock) and Geospatial factors (areas at risk). This type of assessment is particularly useful when comparing vulnerabilities at global/regional/national levels while it needs modification before application to for instance flood vulnerability at catchment level. Vulnerability assessments are closely related to risk assessments (C2.01).
- Vulnerability needs to be viewed both as a physical and social issue
- Vulnerability assessments are needed to inform and improve the quality of decision making on adaptation
- Vulnerability assessments has to draw on information about many diverse aspects such as hydrometeorology, water governance, education, health, finance and insurance, ecosystems and technical infrastructure
- Strategies and actions to reduce vulnerability have to be viewed in relation to the robustness vis-a-vis uncertainties about climate change severity and impact, and prioritization can take into account a classification within win-win actions, no regret actions, low regret actions, flexible adaptation actions and regret actions.
- Vulnerability to climate change impacts is best analyzed as an addition to the vulnerability to other changes, natural or human induced, in the river basin
- Vulnerability assessments need to include stakeholder preferences as it involves incomparable factors (“oranges and apples”).