C1.2 Water resources assessment
Water resources assessment (WRA) is a tool to evaluate water resources in relation to a reference frame, or evaluate the dynamics of the water resource in relation to human impacts or demand. WRA is applied to a unit such as a catchment, sub-catchment or groundwater reservoir. It is part of the IWRM approach, linking social and economic factors to the sustainability of water resources and associated ecosystems. Depending on the objective of the assessment, WRA may look at a range of physical, chemical and biological features in assessing the dynamics of the resource.
Traditional water resource assessment aimed to provide the basis for the supply of infrastructure to meet projected needs. Assessments have a much wider remit in an IWRM perspective, incorporating cross-sectoral tools such as:
- Demand assessment, which examines the competing uses of water with the physical resource base and assesses demand for water (at a given price), thus helping to determine the financial resources available for water resource management (see also Economic assessment, C2.8);
- Environmental Assessment and Strategic Assessment collect data on the social and environmental implications of development programmes and projects (C2.6);
- Social assessment, which examines how social and institutional structures affect water use and management, or how a specific project might affect social structures (C2.7);
- Risk or vulnerability assessment, analyses the likelihood of extreme events, such as flood and droughts, and the vulnerability of society to them (see C2.5).
WRA links to the Water Resources Knowledge Base (C1.1) and is a basic input in the planning process (C2). Demand forecasting should use techniques that uncover, for instance, willingness to pay for water at given prices, and further economic analysis will help reveal the true nature of competing water uses. Demand management issues (C3) will also influence the outcome of WRA.
- A water resources assessment often needs to be carried out in several steps of increasing complexity. A rapid water resources assessment may help identify and list the most important issues and identify priority areas. On the basis of this early assessment, more detailed investigations may be required.
- Assessments for large or long-term projects need to include examination of changes in land use and possible soil degradation as well as climate variability and change.
- Linking water resources assessment to Environmental Assessment (EA) (C2.6) has been shown to build cross-sectoral linkages and heighten awareness of key issues.
- Strategic assessment can help in the analysis of changes in the capacity of a river basin, to protect both quantity and quality.