Water Quality Monitoring Program in Great Smoky Mountains National Park: Statistical reassessment of spatial and temporal design considerations.

Schwartz, John; Probst, Timothy; Gonzalez, Adrian; Kulp, Matt

The overall I&M Program in Great Smoky Mountains National Park (GRSM), including water quality, is currently being revamped to reflect new issues, and to standardize the program to the Park Service-wide vital signs approach. A conceptual plan for vital signs monitoring was completed during FY10. Six watersheds have been selected for GRSM’s Vital Signs Monitoring Program, including: Abrams Creek, Cataloochee Creek, East Prong Little River, Hazel Creek, Middle Prong Little Pigeon River, and Deep Creek. In addition, the Cosby-Rock Creek watershed has been added to the water quality monitoring program because its chemistry differs from other watersheds and is showing a downward trend in water quality over time (e.g., decreasing pH, increased nitrate). Although watersheds have been selected for the Vital Signs Monitoring Program, additional information is needed to ensure that the number and frequency of samples per incremental elevation class and the sampling frequency will be sufficient to detect trends in stream water quality. Specific study objectives included the following: 1) characterize stream chemistry along an elevation gradient; 2) identify time trends in stream chemistry for different elevation ranges; and 3) assess statistical power for existing variances of stream chemistries for different time periods and elevation ranges, and estimate the number of samples with sufficient power to detect future trends in water quality. The key controlling environmental variable for stream chemistry in GRSM is elevation, where it is observed that pH, acid neutralizing capacity (ANC), and base cation concentrations decrease with increasing elevation, nitrate and dissolved aluminum concentrations increase with increasing elevation, and sulfate appears not to vary significantly with elevation. Based on an agglomerative hierarchical clustering method, results from two datasets suggest that vital signs monitoring should include the following elevation classes: 1) 1,000 ft to 2,000 ft; 2) 2,000 ft to 3,000 ft; 3) 3,000 ft to 3,500 ft; 4) 3,500 ft to 4,500 ft; 5) 4,500 ft to 5,000 ft; and 6) > 5,000 ft. The statistical power analysis found that a study design based on 1,000-ft intervals (six elevation classes from 1,000 ft MSL to > 5,000 ft) sampled every other month will generate sufficient data within about 4 to 5 years with a minimum number of samples equal to 109. The current sampling design criteria, which include bimonthly sampling for six elevation classes, and six watersheds, will allow for a statistical trends analysis to be conducted separately per watershed and per elevation class across the park.

Water Quality Monitoring Program in Great Smoky Mountains National Park: Statistical reassessment of spatial and temporal design considerations.

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