Civil Engineering

 

Date of this Version

10-2012

Citation

Florek, M. (2012). "Characterization of Runoff in Two Urban Watersheds in Lincoln, Nebraska," MS thesis, University of Nebraska-Lincoln.

Comments

A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Civil Engineering, Under the Supervision of Professor Bruce I. Dvorak. Lincoln, Nebraska: October, 2012

Copyright (c) 2012 Michael James Florek III.

Abstract

Characterization of runoff water quality and conditions for two urban watersheds in Lincoln, NE, was performed using data collected from 2008-2012. Water quality data from in-stream probes and storm sampling was combined with soil sample data, geographic information system (GIS) modeling, and nutrient isotope composition analysis to provide a more detailed picture of runoff mechanisms in the Taylor Park and Colonial Hills watersheds.

Soil sample data and GIS modeling were used to compare physical characteristics of the urban watersheds. Taylor Park and Colonial Hills are relatively similar, save for Colonial Hills being six times as large. Its time of concentration, 140 minutes, was found to be much longer than at Taylor Hills, 60 minutes. Water quality data collected for a previous study by Fisher (2011) was used to compare seasonal mass loadings of turbidity and total suspended solids (TSS). The ratio of turbidity to TSS was found to be higher at Colonial Hills for small storms and higher at Taylor Park for large storms, suggesting that large particles in runoff at Colonial Hills reach the watershed outlet in large storms, but are captured in small storms.

Isotope analysis was conducted on soil samples collected in 2011 and 2012 and water quality samples collected in 2011 in order to identify possible sources of nutrients in storm water runoff. Samples were tested for 18O-NO3, 15N-NO-3, and 18O-PO4 composition. Analysis showed that atmospheric deposition of nitrogen, in the form of precipitation on impervious surfaces, is likely to be a meaningful source of nitrate in the two watersheds.

Soluble reactive phosphorus (SRP) concentration and 18O-PO4 composition were compared over the course of several storms. SRP showed a trend of increasing as a storm continued, while 18O-PO4 appeared to change over time in larger storms. Estimated mass loadings of SRP and Total Phosphorus when SRP is high suggest meaningful phosphorus contribution during the later part of storms. These results may suggest that erosion of soil, such as stream bank soil, may be a source of phosphorus in storm water runoff.

Adviser: Bruce I. Dvorak

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