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29 n .., r, , .~ () ~ ,I ':" '~t ;;,] Nutrients The biological productivity in lakes is dependent on the availability of nutrients within the aquatic system. Those elements that are needed in large quantities for plant growth, such as nitrogen, phosphorus, and carbon, are termed major nutrients or macronutrients. Those elements needed in minute quantities, such as molybdenum and zinc, are termed as trace nutrients or micronutrients. Although there are several ways for nutrients to enter a lake, most nutrients originate from surface-water inflow and cultural input such as septic-tank discharge. Once in the lake, nutrients are subjected to various removal and(or) recycling functions. Large quantities of nutrients can be removed from the water by chemical reactions, adsorption onto sediment and subsequent deposition, and biological utilization. These processes may be reversed, however, through biochemical action. The conversion of inorganic nutrients into biomass (nutrient removal) within a zone of substantial phyto- plankton productivity may be reversed in the profundal zone where nutrients are recycled back into solution as byproducts from decomposition. These processes often produce uneven chemical and nutrient distributions when the lake is stratified. Attempts to classify lakes into trophic categories commonly are based on the concentrations of macronutrients. Nitrogen and especially phosphorus currently are considered the major nutrients that affect the rate of eutro- phication in lakes and reservoirs. Sawyer (1947) states that nuisance phytoplankton conditions can occur when inorganic nitrogen concentrations exceed 0.3 mg/L and phosphorus concentrations exceed 0.01 mg/L. Vollenweider (1968) compared the input of nitrogen and phosphorus to lake mean depth and determined that shallower lakes are more sensitive to nuisance growth conditions than deeper lakes. A short hydraulic residence time (small capacity-inflow ratio), however, may control phytoplankton production by maintaining rapid flushing rates (Welch, 1969). Various attempts to control the rate and undesirable effects of eutrophication are summarized by Dunst and others (1974). Nutrient data for Kenney Reservoir are listed in tables 6 and 7; nutrient data for the White River (site 3) for water years 1985-87 were compiled from the U.S. Geological Survey WATSTORE (Hutchison, 1975) computer data base. Concentrations of ammonia, nitrite plus nitrate as nitrogen, and organic nitrogen that were determined for sites 1, 2, and 3 during 1985-87 are shown in figures 14, 15, and 16. The concentrations of phosphorus are shown in figure 17. Concentrations of total organic carbon in the White River (site 3) and near the inlet (site 2) generally ranged from about 2 to 12 mg/L. Concen- trations of total organic carbon at site 1 ranged from about 2 to 6 mg/L and generally were less than at sites 2 and 3. Concentrations of total organic carbon at site 3 were greatest during spring runoff; variations in concentra- tions of dissolved organic carbon generally were independent of flow.