Browsing by Author "Cada, Peter"

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Open Access
Changes in stream ecosystem structure as a function of urbanization: Potential recovery through stream restoration
(2007-05) Cada, Peter
I documented reach scale changes in the physical structure of 12 stream channels in the summer months of 2006, comparing four small streams draining forested catchments with eight streams from developed watersheds of similar catchment size. Study sites in four of the urban streams are within recently implemented natural channel design restoration projects. To assess whether restoration projects increase stream habitat and flow heterogeneity and increase water exchange with floodplain and hyporheic sediments I compared reach-scale geomorphic (e.g. slope, cross section, degree of incision, variation in water depth) and hydrologic (e.g. transient storage volume (TS), surface-water groundwater exchange, fine scale variation in velocity) features of each stream. I used ArcGIS to compile watershed maps and to produce detailed maps of reach habitat for each stream, and the hydrologic model OTIS-P to estimate transient storage from field rhodamine releases. Minimally impacted reaches were found to have shallower average depths with a greater variation in depth than urban or restored stream reaches. Streams restored to provide habitat had the lowest flow habitat heterogeneity of the three stream classes. Channel incision was the only physical channel feature for which the urban restored streams were more similar to the forested streams than the urban degraded condition. Surprisingly, I was unable to detect significant differences in transient storage volume or hyporheic exchange between our three stream classes. My results suggest that restoration designs are placing inadequate attention on recreating the physical template seen in less degraded streams.
Open Access
Wastewater Pollution from Petrochemical Refining Industries: Modernizing Treatment Technologies & Downstream Impacts
(2024-04-26) Satagopan, Nanditha Ram; Furr, Tiajahlyn; Li, Dili
The Clean Water Act of 1972 was created to regulate pollutant discharge into the surface waters of the United States and aims to produce fishable, swimmable waters across the U.S. and eliminate the pollution of navigable waters by 1985. Over the last few decades, petrochemical refineries have expanded capacity and the volume and variety of the pollutants they discharge have increased exponentially. Through the Clean Water Act, the EPA is required to set effluent limit guidelines (ELGs) for discharge based on the best available treatment technologies (BATs). However, revisions have not been made since 1985 and standards do not reflect the advances in the BATs used by oil refineries. Our research aims to provide evidence to the Environmental Integrity Project (EIP) to advocate for updated pollution control standards enforced by the Clean Water Act, identify possible explanatory factors for differences in effluent levels, and evaluate the impacts on downstream populations disproportionately affected by refinery discharges.