Most groundwater conservation and management efforts have focused on protecting groundwater for drinking water and other human uses. In addition, while there are numerous efforts by conservation organizations and government agencies to protect and restore surface water quantity and quality for the benefit of aquatic ecosystems, there are few similar efforts focused on identifying and mitigating threats to groundwater quality and quantity. To address this disparity, The Nature Conservancy is working to identify conservation actions that will protect groundwater-dependent ecosystems and species (GDEs).
In this assessment we identified, analyzed and mapped (i) GDEs and (ii) threats to GDEs due to changes in groundwater quantity and quality. To manage the information and summarize the results at an appropriate scale, we divided the state into fourteen regional analysis units, which are based on the administrative basins of the Oregon Water Resources Department.
Each of these regions has similar biota and groundwater processes due to the relative homogeneity of hydrogeologic, ecological and climatic conditions. We further subdivided each region into watersheds, using the sixth level Hydrologic Units of the USGS (referred to as HUC6) as the watershed boundaries. Each HUC6 was evaluated for the presence of GDEs and activities that threaten groundwater quantity and quality. Thus, the analysis and summary of findings were completed at the HUC6 scale, rather than for the exact locations of the GDEs and land use activities.
The analysis relies on existing, relatively coarse datasets. Because there is limited information about both groundwater-dependent biota and the condition of groundwater across the region, we used a suite of surrogate indicators to develop new analytical methods. In general, these indicators highlight the potential threat to groundwater rather than actual effects on groundwater quantity and quality. Given the coarse nature of the datasets and the lack of strong analytical relationships, this assessment functions as both an inventory of information and a screening tool to identify high-priority areas for the conservation of groundwater-dependent ecosystems.
Click on the document above to access the main report. Links to detailed appendices and related articles are below.