In this study to identify the current state of water vulnerability at the county scale of the Columbia River Basin, we employed the index-based approach of Sullivan (2011) that quantifies the water vulnerability as an integration of several indicators representing socio-economic and environmental status of the water resources system. We chose water supply, water demand, and water quality as our indicators on the basis of simplicity, data availability, repeatability, and consistency, including the range of the raw data. These vulnerability indicators can be grouped into three classes representing hydro-climatologic, environmental and socio-economic status of the study area. On the basis of the classes we assign equal weights to the indicators, assuming each indicator has the same level of importance. Although it is unlikely that most variables carry equal weight, determining the relative importance of all variables is fraught with uncertainty; thus we consider this a conservative approach. Key factors in both supply side vulnerability (e.g., water quantity and water quality) and water demand vulnerability are shown in the graphic below.
This study examined water resource vulnerability at a county scale using multiple indicators that encompass three major dimensions of water vulnerability: supply, demand, and quality. As one of the first comprehensive assessments of vulnerability conditions the CRB, we found: i) spatial patterns of water resource vulnerability varied distinctly in a large heterogeneous river basin; ii) major controls of spatial water resources vulnerability differed from one region to the other (e.g., Willamette River basin drivers were associated with anthropogenic effects on water quality, Upper Snake River basin drivers were associated with climate and land use); and iii) water supply and demand vulnerability were positively related, but were there was no observable trend with respect to water quality vulnerability.
Estimated change in water vulnerability from 1985 to 2005.
Based on county level water uses from 1985 to 2005, we estimated changes in water vulnerability calculated by total water use (MIA- municipal, industrial, and agricultural) divided by total annual flow for 1985 and 2005.
Sullivan, C.A. 2011. Quantifying water vulnerability: a multi-dimensional approach. Stoch. Environ. Res. Risk Assess. 25: 627-640.