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® Create GIS soils coverage characterizizig the infiltration capacity of the soils for the Lake Owasso watersheds. The GIS soils coverage will be based on information from the most recent Ramsey County NRCS soil survey. The GIS soils coverage will be used to develop hydrologic input parameters for P8 modeling and as a screening tool for identifying potential BMP locations. After all of these data are collected and analyzed, Barr will develop a detailed P8 model of the lake's watershed. Setting up the P8 models will include entering all of the pond and wetland areas and volumes, outflow devices, overflow elevations and outflow destinations for each drainage area in each lake's subwatershed, as well as gathering land use information for each drainage area. Once the P8 model for the lake's watershed is created and calibrated to inflow monitoring data they will be used to generate water and phosphorus budgets for the lake under existing land use conditions. Task 5: lZec®ncile the hyclr®l®gic and ph®sph®rus budgets t® ®bser-ved in®lake c®nditi~ns using a lake water- quality m®del Expected Cost: $18,110 Lakes receive phosphorus loads from both external sources (stonnwater runoff and atmospheric deposition, primarily) and internal sources (recycle of plant- or sediment- bound phosphorus). While stonnwater runoff volumes and phosphorus loads will be estimated with P8, a separate model is required for simulating the in-lake nutrient processes and resulting phosphorus budget of the lake. An in-lake mass balance model developed by Barr will be used to estimate phosphorus concentrations in Lake Owasso. The in-lake model takes into account the impacts of external (watershed runoff, atmospheric deposition, septic systems, etc.) and internal phosphorus sources (oxic and anoxic sediment-release, aquatic plant decay, rough fish, etc.) on the predicted in-lake phosphorus concentration. The in-lake model can be calibrated by comparing the predicted phosphorus concentrations in Lake Owasso with monitoring data and adjusting model parameters to closely match monitored Lake conditions. This partitioning of phosphorus sources allows for better assessment of BMP benefits and more precise estimates of in-lake concentrations at various times during the summer recreational period. In order to accurately model the potential internal load of phosphorus that the lake receives from its seasonally anoxic sediments, Barr will collect five sediment core samples from Lake Owasso. These sediment cores will be analyzed for mobile- phosphorus, the fraction of sediment phosphorus that maybe recycled back into the water column, from anoxic lake sediments. This recycled phosphorus generally becomes available for algal uptake in the late-summer when thermal stratification breaks down and the lake mixes. P:\wr\li\pip\2006\6069 -Lake Owasso\Lake_Owasso_UAA_Scope_Pinal_Jan 12 07.doc