Waters in the Lake Waco-Bosque River watershed, which includes the North Bosque River, have been listed on the 303(d) list of impaired waters in 1992, 1994, 1996, 1998, and 2000 for nutrient enrichment (i.e., elevated nutrient concentrations and excessive algal growth). Since the 1990s, the Texas Institute for Applied Environmental Research (TIAER) has conducted water quality monitoring in the watershed. Using those data, TIAER researchers identified suspended algae as a concern with nutrients as one factor impacting algal growth.
The researchers sought a way to reduce impairment in North Bosque River by first establishing predictive relationships between nutrient concentrations and algal blooms and then setting nutrient targets. Using both in situ and laboratory data, they identified soluble reactive phosphorus (P04-P) as the limiting nutrient in the North Bosque River. They found that downstream sites and reference sites had the highest frequency of significant limitation. Researchers considered four approaches to developing the predictive relationship: (1) statistical relationships from monitoring data between annual average chlorophyll a and phosphorus concentrations; (2) comparing screening levels for chlorophyll a, with predictive relationships from the first approach; (3) using a reference site to set a benchmark for ecosystem function; and (4) comparing the relationship of in situ productivity to maximum potential productivity. The researchers applied those approaches in identifying potential P04-P targets values ranging from 15 µg/L to 50 µg/L as an annual average (Kiesling et al. 2001).
Reference:
Kiesling, R.L., A.M.S. McFarland, and L. M. Hauck. 2001. Nutrient Targets for Lake Waco and North Bosque River: Developing Ecosystem Restoration Criteria. TR0107. USDA Prepared for Lake Waco-Bosque River Initiative. Accessed October 2016. http://tiaer.tarleton.edu/pdf/TR0107.pdf Exit.