Lake Erie Spring Tributary Data

Spring (March-July) phosphorus loads, loading targets and discharge for priority Lake Erie tributaries from 2008-2020. Includes both total phosphorus (TP) and soluble reactive phosphorus (SRP) as well as flow-weighted mean concentrations (FWMC) for both. The U.S. and Canada set phosphorus reduction goals (40 percent of 2008 loads) for eight priority tributary watersheds for both total and soluble reactive phosphorus (SRP) during March-July. SRP refers to phosphorus that is in a dissolved state and is of particular interest because it is the easiest form of phosphorus for algae to use to fuel growth. The targets for these tributaries are expressed in terms of the flow weighted mean concentration (FWMC), which is a way to normalize the load for varying flow conditions. This is important because much of the load is delivered during storm events. It means that efforts to reduce the load must also include efforts to reduce the amount of flow (runoff). FWMC also provides an important backstop and relative measure of whether phosphorus control efforts are actually having an impact. For example, in a dry year, the load may be low due to less runoff, but the FWMC will still be high if the proportion of phosphorus in that runoff is high. The calculation of spring load requires high frequency flow and water quality monitoring, which is now in place for all nearshore priority tributaries. Not all tributaries had monitoring in place going back to 2008.