| In the second chapter a customized version of the Soil and Water Assessment Tool (SWAT) model was used to predict hydrology and water chemistry constituent fate and transport for the Olentangy River watershed for the time period 1985--2002. The customized version of SWAT simulates a restrictive layer of material in the soil profile and its impact of subsurface drainage, watershed hydrology, and nutrient and sediment transport. Model parameterization and calibration are presented. Predictions of stream discharge were evaluated at three locations with stream discharge records, however only one location (USGS gage at Claridon, Ohio) was not impacted by Delaware Dam which controls discharge. Regression results for annual and monthly observed and predicted discharge at the Claridon gage provided coefficient of determination values of 0.84 and 0.81, respectively. A similar analysis of annual and monthly discharges with the Nash-Sutcliffe statistic provided coefficient of efficiency values of 0.81 and 0.77, respectively. SWAT predictions for water chemistry constituents for the Olentangy River at Claridon and Worthington, Ohio ranged from 0.32--0.37 mg/l, 3.6--3.8 mg/l, and 114--172 mg/l for total phosphorus, nitrate-nitrogen, and total suspended sediment, respectively. Measured water quality from two studies conducted on the Olentangy and Scioto Rivers provided ranges of 0.23--0.49 mg/l, 3.4--4.4 mg/l, and 47--170 mg/l for total phosphorus, nitrate-nitrogen, and total suspended sediment, respectively. Following calibration of the model all land use in the watershed was changed to forest, prairie, or wetlands to predict the potential water quality of pre-European conditions in the watershed. The results show that delivery of sediment, total phosphorus, and nitrate-nitrogen to the stream system has increased by factors of approximately 50, 20, and 3, respectively, for most subwatersheds in the Olentangy River watershed.; In chapter 3 the calibrated SWAT model was used to predict the potential water quality benefits of alternative management scenarios and conservation practices in the Olentangy River watershed. Alternative management scenarios and conservation practices that were evaluated include: (1) alternative crop rotations, (2) alternative fertilizer application rates, (3) alternative types of tillage, (4) timing of tillage operations, and (5) buffer strips of various widths.; Another study was conducted to develop a geomorphology assessment index to evaluate dynamic equilibrium at study sites in the Olentangy River watershed. Regional curves were developed using geomorphology data from study sites impacted by a variety of disturbances. The geomorphology assessment index was developed to provide a logical and minimally biased framework to assess dynamic equilibrium at study sites in the Olentangy River watershed.; In chapter 5 a statistical analysis was conducted to examine the relationships between stream biology and environmental variables such as water quality, habitat, and geomorphology. The spatial location of a study site within the drainage network and its impact on the structure of the biological community was also evaluated. (Abstract shortened by UMI.)... |
