Browsing by Subject "watershed management"

Now showing 1 - 4 of 4
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    Analysis of stormwater runoff from impervious surfaces in downtown Minneapolis, MN
    (2021-09) Faust, Brittany
    Urban stormwater runoff is a major concern for water quality. Impervious surfaces, especially in urban environments, can allow contaminated stormwater direct access to receiving waterbodies. Impervious surfaces make up nearly 90% of land cover in downtown Minneapolis, Minnesota. When rain falls or snow melts, pollutants quickly transfer from those surfaces into nearby waterways. A study of stormwater runoff from impervious surfaces in downtown Minneapolis, Minnesota USA was conducted to understand potential impacts of different types of impervious surfaces (i.e., streets, sidewalks, parking lots and rooftops). The results of this study could be used to inform urban stormwater management strategies, particularly when the makeup of the area is mostly impervious surfaces. Between summer 2017 and spring 2018, a rainfall simulator was used to deliver water upon street, sidewalk, and parking lot sites, which removed differences in rainfall characteristics, and tested the role of varying surface types and seasonal differences. Characteristics of rooftop runoff were studied using natural rainfall and snowmelt event data collected year-round with automated samplers and rain gauges. Results showed that the first flush of runoff contained higher pollutant concentrations compared to the whole rain event, and water quality differences for all of the surfaces were relatively minor for the summer and fall seasons. The greatest difference was observed with higher pollutant concentrations occurring in the spring for all sites, particularly on streets. Higher than expected concentrations of chloride in the winter occurred from roofs, though concentrations were overall much smaller than the ground sites in the spring. Street event mean concentrations (EMCs) were the highest across different stormwater constituents, including chloride, total phosphorus, and total suspended solids. For each stormwater constituent, when the average EMC value was used for calculating pollutant loading instead of individual surface type EMC values, street contributions were underestimated, and the other surface types were overestimated due to the higher pollutant concentrations from streets than other impervious surfaces.
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    Phosphorus-sediment interactions and their implications for watershed scale phosphorus dynamics in the Le Sueur River Basin
    (2018-08) Baker, Anna
    Phosphorus is a leading pollutant of global surface waters, and sediment is a known driver of phosphorus loading to downstream receiving waters. This master’s thesis investigates sources and dynamics of phosphorus in the Le Sueur River basin in southern Minnesota, a highly agricultural watershed whose glacial history has rendered it vulnerable to massive erosion, and which contributes disproportionately to downstream sediment and phosphorus loading. We develop a mass balance for sediment-derived phosphorus, incorporating sediment-total and dissolved phosphorus into a robust sediment budget describing sources and sinks of sediment to this system. This budget explores the extent to which agricultural top soil and upland ditch-banks, and eroding near channel features such as bluffs, stream banks, and ravines, can be implicated for phosphorus loading to this basin. Further, we explore the extent to which in-stream processing alters the fate, bioavailability, and persistence of phosphorus in this system via the incorporation of sorption experimental data into this budget. Our results show that fine (silt and clay sized) source sediment can only account for at most 24% of the total phosphorus exported from the Le Sueur River. These results suggest that sediment and phosphorus sources are largely decoupled, and that if we managed 100% of fine sediment erosion we would only reduce phosphorus loading by 24% or less. Sorption tests were used to examine the role of fine sediment as a source or sink for phosphorus. Results of these tests demonstrate that agricultural sediments donate phosphorus, while near channel sediments bind phosphorus from the water column. Incorporation of these results into our budget indicates that 2-24% of total phosphorus may be in particulate form as a result of in-stream equilibrium processes between sediment and dissolved orthophosphate in the water column. Sorption of dissolved phosphorus by sediment may depress dissolved phosphorus load by as much as 31%. These results point to the importance of understanding dissolved phosphorus source and dynamics, and to the management of both sediment and dissolved phosphorus source being critical to addressing excess phosphorus in this basin.
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    RECOVERY OF SEDIMENT CHARACTERISTICS IN MORAINE, HEADWATER STREAMS OF NORTHERN MINNESOTA AFTER FOREST HARVEST
    (2010) Merten, Eric, C.; Hemstad, Nathaniel, A.; Kolka, Randall, K.; Newman, Raymond, M.; Verry, Elon, S.; Vondracek, Bruce
    We investigated the recovery of sediment characteristics in four moraine, headwater streams in north-central Minnesota after forest harvest. We examined changes in fine sediment levels from 1997 (preharvest) to 2007 (10 years postharvest) at study plots with upland clear felling and riparian thinning, using canopy cover, proportion of unstable banks, surficial fine substrates, residual pool depth, and streambed depth of refusal as response variables. Basin-scale year effects were significant (p < 0.001) for all responses when evaluated by repeated-measures ANOVAs. Throughout the study area, unstable banks increased for several years postharvest, coinciding with an increase in windthrow and fine sediment. Increased unstable banks may have been caused by forest harvest equipment, increased windthrow and exposure of rootwads, or increased discharge and bank scour. Fine sediment in the channels did not recover by summer 2007, even though canopy cover and unstable banks had returned to 1997 levels. After several storm events in fall 2007, 10 years after the initial sediment input, fine sediment was flushed from the channels and returned to 1997 levels. Although our study design did not discern the source of the initial sediment inputs (e.g., forest harvest, road crossings, other natural causes), we have shown that moraine, headwater streams can require an extended period (up to 10 years) and enabling event (e.g., high storm flows) to recover from large inputs of fine sediment.
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    Tillage Best Management Practices for the Minnesota River Basin Based on Soils, Landscape, Climate, Crops, and Economics
    (St. Paul, MN: University of Minnesota Extension Service, 1996) Moncrief, John F.; Evans, Samuel D.; Randall, Gyles W.; Senjem, Norman B.; Lueschen, William E.; Olson, Kent D.
    This book is a compilation of the following six publications, which are also available individually: Description of the Minnesota River Basin and General Recommendations of Residue Management Systems for Sediment control (FO-6673); Sediment Problems and Solutions for the Minnesota River (FO-6671); Tillage Best Management Practices for Corn-Soybean Rotations in the Minnesota River Basin (FO-6676); Tillage Best Management Practices for Continuous Corn in the Minnesota River Basin (FO-6672); Tillage Best Management Practices for Small Grain Production in the Upper Minnesota River Basin (FO-6674); Economic Comparison of Incremental Changes in Tillage Systems in the Minnesota River Basin (FO-6675).