Contract Description:

This contracting period represents the third year of a nutrient supplementation project on Dworshak Reservoir.  This project is a joint venture between the U.S. Army Corps of Engineers (USACE) and the Idaho Department of Fish and Game (IDFG).  The USACE will supplement the reservoir with nitrogen to promote an improved nitrogen to phosphorus  ratio and increase foodweb efficiency.  The IDFG will be responsible for collecting limnological samples, which will be used for in-season management of nutrient supplementation and for evaluating project effectiveness.  The USACE has contracted TG-Ecologic to interpret the results of limnological sampling for recommending in-season adjustments to the amount of fertilizer to be applied.  Fish monitoring will also be conducted by the IDFG and, combined with limnological data, will allow for an overall assessment of project effectiveness.
Several changes to the limnological sampling and fish monitoring have been incorporated into the current contract.  Since we have two years of data that span both higher and lower than normal run-off conditions, we have a better understanding of how the reservoir will respond to nutrient supplementation under a wide range of reservoir inflows.  Thus, we scaled down our collection of limological samples used for both in-season management and assessment of the project.  Under this new protocol, the primary monthly sampling event will remain the same, with the exception of eliminating the 30-10 m vertical plankton tow.  However, the secondary monthly sampling event will not include any sampling of the hypolimnion, total dissolved solids, pico-plankton, or zooplankton (for classical analysis).  A detailed description of the limnological sampling is provided in the 2009 Quality Assurance Project Plan (QAPP), which is attached to this project.
Implementation of the nitrogen supplementation is once again expected to be conducted under a Consent Order from the Idaho Department of Environmental Quality (IDEQ), because a National Pollution Discharge Elimination System (NPDES) permit has still not been reviewed and issued by the Environmental Protection Agency (EPA).  For this reason, and the fact that Dworshak Reservoir has responded differently than other lakes or reservoirs for which similar programs have already been implemented, it will be necessary to continue collecting most limnological data semimonthly.  The importance of this sampling rate was illustrated in 2008 when a bloom of blue-green algae occurred between the first sampling periods in July and August.  Data on this bloom and conditions that lead to it would have been absent if a single monthly sampling regime had been used.  In order to maintain this sampling rate, even with a reduction in the number of parameters to be sampled, we will need to obtain an additional $35,000 from the Bonneville Power Administration (BPA) through the Budget Oversight Group (BOG) process.
The project has progressed well during the first two seasons.  Nitrogen supplementation has resulted in a more desirable plankton community.  Although kokanee were not necessarily longer than typically expected during years of similar densities (although this analysis is preliminary), they were considerably heavier.  This has lead to positive feedback from anglers despite lower than average kokanee abundance.  While undesired blooms of inedible diatoms and blue-green algae did occur, we gained greater understanding of how the reservoir responds to nutrient supplementation.  We expect effects of the supplementation to be incremental, with benefits seen at a higher trophic level in each subsequent year.  With this in mind, any noticeable benefits to the kokanee population this early in the project should be viewed as encouraging.  A more thorough analysis of the effects of supplementation is underway and will be included in the FY09 annual report.  Data from previous years have been compiled into a master database to assist with future analyses.