ET-4D2 (6/24/05)
Chemical Integrity: Existing Phosphorus Reduction Targets

Table 1. Existing Phosphorus Reduction Targets

Target/Source/Indicator Level

Target 1A: Lake Erie phosphorus concentration targets are 15 µg/l for the western basin and 10 µg/l for the central and eastern basins (Level 4).

Baseline (2001): The five year running average phosphorus concentration target was not met in the western basin (16.2 µg/l) and was met in the central basin (6 µg/l). However, overall, spring concentrations and loadings to the lake seem to be rising, raising the need for continued monitoring and research on that issue.

Target 1B: To achieve phosphorus target concentrations in Lake Erie, a lake-wide phosphorus loading reduction of 2,000 metric tons/year is necessary. The Ohio portion of the established Lake Erie phosphorus loading reduction goal is 1,385 metric tons (Level 3).

Baseline (2003): In 1976, the entire U.S. Lake Erie tributary diffuse total phosphorus load was 6675 metric tons per year from 1.923M hectares of cropland and 0.882M hectares of pasture. In 1983 the Great Lakes Water Quality Agreement (GLWQA) established the need for a 2000 metric tons/year phosphorus loading reduction.

Ohio trends in existing phosphorus loads to the lake have been recorded since 1982. The general trend is decreasing phosphorus loadings. In certain years there has a been a decrease of 1,385 metric tons or more from the 4,000+ metric ton loading of 1982. This loading reduction is not consistent, reflecting the influence of weather. Intense storms that occur at times when fields are bare can result in one storm event dominating the entire annual phosphorus load to the lake.

Target 2: Per the Scioto CREP, by 2013, reduce phosphorus loading flowing into the Ohio River from the Scioto River basin by 20% (Level 3).

Baseline: The Scioto River basin discharges about 1,000 metric tons of phosphorus annually to the Ohio River. Additional details are available in "Assessment of Overland Runoff Nonpoint Source Pollution, 2003".

Target 3: Per the Upper Big Walnut CREP, by 2012, reduce nutrient loadings flowing into Hoover Reservoir by 30%, through implementation of 3500 acres of conservation practices and 500 acres of conservation easements (Level 3). The percentage reduction in phosphorus is tied to the recommended sediment reductions for the same watershed, as phosphorus attach to soil particles.

Baseline: This target is based on protecting drinking water quality for the City of Columbus. Current load estimates are based on concentration values obtained from monthly reservoir water quality monitoring. Phosphorus concentration values range from 0.05 to 0.10 mg/l. Recent taste and odor producing biological events suggest that nutrient stimulation of these growths may be occurring.