Lake Tapps Water Quality Monitoring

Lake Tapps is a large reservoir created by flooding two small lakes with water from the White River to generate power. Cascade Water Alliance is now managing the lake as a recreational resource while it plans its use as a future water supply. Herrera was awarded an on-call limnology contract in 2017 that included seven task orders:

1. Prioritization and estimating costs of activities specified in the Lake Tapps water quality management work plan
2. Recommending changes to the Lake Tapps comprehensive water quality monitoring plan
3. Surveying other surface water utilities to describe their operations, policies, problems, and monitoring program
4. Evaluating the effects of reservoir operations on water quality and aquatic plant growth in Lake Tapps
5. Monitoring inputs of fecal bacteria and phosphorus to Lake Tapps from septic systems using fluorometry to detect hot spots and genetic fingerprinting to confirm human contamination, and working with the health department to correct the identified sources
6. Monitoring stormwater inputs to the lake inflow canal to identify significant sources of nutrient pollution and contamination by PFAS and other emerging contaminants of concern for drinking water supplies
7. Monitoring illicit discharges from a dairy farm to determine the extent of nutrient pollution and contributions from cow manure and brewery wastewater

Herrera was also awarded a 2-year, $500,000 water quality monitoring contract in 2019. Herrera installed state-of-the-art monitoring equipment including two YSI multimeters with chlorophyll and phycocyanin pigment probes, with one in the lake on a solar-powered continuous profiler and one in the lake inlet. Real-time data were routinely downloaded online to validate equipment function and data accuracy. Limnologists conducted routine monitoring of many field and laboratory parameters monthly in the winter and twice monthly in the summer and monitored regulated and unregulated drinking water parameters twice yearly. Herrera analyzed data for the water year 2020 report using advanced graphical and statistical analysis of temporal and spatial trends in the lake’s trophic state and drinking water parameters and are currently evaluating the entire baseline data set in preparation of the water year 2021 report.