Reid, N. J. and S.K. Hamilton
Presented at the All Scientist Meeting (2004-10-08 )
Impoundments change the characteristics of a water body from a river to lake, affecting chemical, physical and biological characteristics. Two reservoirs were sampled weekly in order to quantify the roles of reservoirs as sinks for nutrients. Lake Allegan is 1587-acre hypereutrophic impoundment, and is located 43 miles downstream of Morrow Lake, a 1000- acre eutrophic impoundment. No major tributary inputs exist between the reservoirs. Despite their spatial proximity, a Total Maximum Daily Load for phosphorus was developed for Lake Allegan to control summer algal blooms, whereas Morrow Lake lacks summer algal blooms. The inflow and outflow waters of Lake Allegan and Morrow Lake were sampled and analyzed for inorganic nitrogen forms, phosphorus, major solutes and chlorophyll а. In both reservoirs there is a decline in SRP from inflow to outflow, and increase in PP from inflow to outflow. Algal biomass build-up between Morrow Lake and Lake Allegan as the river passes through smaller decommissioned impoundments, which decrease stream flow enough for substantial algal growth. The cumulative algal bloom expressed in Lake Allegan is exacerbated by old impoundments remnants.
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