New Hampshire's Experience and Ideas for Integrated Water Quality Assessments: Combining Probabilistic and Targeted Surveys to Assess Water Quality at Multiple Scales
Paul M. Currier, Philip R. Trowbridge and W. Gregg Comstock
New Hampshire Department of Environmental Services
For the 2004 Integrated report, New Hampshire cataloged its waterbodies into assessment units using the National Hydrography Dataset. We implemented an Environmental Monitoring Database (EMD) for water quality data from cooperating organizations, linking the data to our waterbody catalog. We performed automated assessments for 305(b) and 303(d) reporting using EMD and the Assessment Database. This worked well for 303(d) listing, but the large number of assessment units makes a census approach to comprehensive assessment for 305(b) reporting infeasible. We used the National Coastal Assessment data for estuaries as a test case and compared the results of targeted assessments with comprehensive probability assessments for aquatic life and recreation uses. With probabilistic surveys, we were able to determine aquatic life use support status for over 60 percent of estuarine waters and recreation use support for about 90 percent. In contrast, 52 percent of estuarine waters were assessed for aquatic life and 75 percent for recreation using targeted sampling data. Sampling data density for the estuaries is about an order of magnitude greater than for other waterbody types, so we expect that probabilistic methods have a clear advantage for comprehensive assessment of all waterbody types at the large watershed, statewide, and national scales. Our Comprehensive Monitoring Strategy incorporates the results of this analysis. It proposes state-level probabilistic surveys by waterbody type combined with targeted sampling by volunteers and watershed organizations for problem identification and 303(d) listing. This strategy will provide good integration with national probabilistic surveys while supporting watershed-scale assessments and decision-making.