Browsing by Author "Baker, Lawrence A."

Now showing 1 - 6 of 6
  • Thumbnail Image
    Item
    Adaptive Management to Improve De-Icing Operations
    (Minnesota Department of Transportation, 2021-03) Baker, Lawrence A.; Wilson, Bruce; Klimbal, Doug; Furuta, Dan; Friese, Melissa; Bierman, Jacob
    Road de-icing is a major cause of chloride impairment in Minnesota's urban waters. The goal of our study was to develop an adaptive management (AM) strategy to reduce chloride impacts caused by de-icing operations. The AM process was informed by our analysis of chloride movement in a residential watershed, providing feedback to the street department of our collaborator, the City of Edina. A key finding was that most the chloride movement occurred during a small number of events, with half of annual chloride movement occurring in less than 50 hours during each of the two years of study. This observation means that targeting these events might be a more effective way to reduce chloride impacts than more generalized approaches. We also found that a significant amount of chloride added to streets during de-icing accumulated in roadside snow piles, likely contributing to groundwater contamination. To address this concern, we developed a spreadsheet tool to estimate steady-state (long-term) chloride concentrations in groundwater. Scenario analyses indicated that groundwater chloride levels in highly urbanized watersheds would eventually exceed water quality standards. We developed a second model, intended for use by urban planners, to estimate the impact of changing the percentage of salted impervious surface on chloride movement in re-developed watersheds.
  • Thumbnail Image
    Item
    Assessment of Stormwater Best Management Practices
    (University of Minnesota, 2008-04) Anderson, James L.; Asleson, Brooke C.; Baker, Lawrence A.; Erickson, Andrew J.; Gulliver, John S.; Hozalski, Raymond M.; Mohseni, Omid; Nieber, John L.; Riter, Trent; Weiss, Peter; Wilson, Bruce N.; Wilson, Matt A.; Gulliver, John S.; Anderson, James L.
  • Thumbnail Image
    Item
    Developing a Street Sweeping Credit for Stormwater Phosphorus Source Reduction: Final Report
    (2020-09) Hobbie, Sarah E.; King, Rachel; Belo, Tessa; Baker, Lawrence A.; Finlay, Jacques C.
  • Thumbnail Image
    Item
    Empirical and Process Models for Acidification and Alkalinity Regulation in Lakes of the Upper Great Lakes Region
    (Water Resources Research Center, University of Minnesota, 1987-11) Brezonik, P.L.; Rogalla, Joy A.; Baker, Lawrence A.
    A large data base was assembled from surveys conducted by several federal and state agencies on approximately 1500 inland lakes in the Upper Great Lakes Region (UGLR) -- northern Minnesota and Wisconsin and Upper Michigan. Data were scrutinized carefully by a variety of quality control procedures, and outliers were eliminated. The quality-assured data base was used to characterize lakes in the three state region according to parameters related to the potential sensitivity of lakes to acidification (e.g alkalinity, pH, conductivity, hydrologic type). A trend of increasing numbers of acidic and very low alkalinity lakes across the region (from west to east) correlates with a similar trend in increasing acidity of precipitation. Drainage lakes are the dominant hydrologic lake type in northern Minnesota, but seepage lakes are most common in northern Wisconsin and Upper Michigan. Most of the lakes in the data base (78%) have organic color levels below 50 chloroplatinate units and are classified as "clearwater" systems. Correction of ion balances for contributions of organic anions was unnecessary for these lakes but was useful in improving ion balances of more highly colored lakes. A factor, CF, defined as the ratio of the average chloride concentration in a lake to the average chloride concentration in precipitation, was used as a surrogate measure for hydrologic data on evaporative concentration. Half the lakes had CF values between 2.3 and 4.4 (mean:3.8). A sulfate enrichment factor (SEF, defined as the sulfate/chloride ratio in a lake divided by the analogous ratio in precipitation) was used to determine whether or not sulfate behaves conservatively in lakes. SEF > 1 indicates the occurrence of terrestrial sources of sulfate in a lake's watershed; SEF < I indicates net loss of sulfate in a watershed or lake (presumably by sulfate reduction), if chloride is assumed to behave conservatively. Only 43t of the lakes exhibited nearly conservative behavior (0.75 < SEF < 1.25), and 40% of the lakes showed evidence of significant sulfate sinks. Two measures of acidification were defined for each lake: change in sulfate (ASO4 ) and change in alkalinity (AAlk), both parameters being the difference between measured (present) lake values and background (pristine levels), which were estimated for each lake by a variety of methods. Several lines of evidence suggest that background sulfate levels in regional precipitation (bSO4p) were between 10 and 20 u.eq/L; multiplying these values times CF for a lake gives the lake's bSO4. Good correlations were found between the two measures of lake acidification (ASO. and AAlk) among the UGLR lakes and especially among precipitation-dominated seepage lakes. A separate data base on chemical quality of atmospheric precipitation across the region was obtained from the Minnesota Pollution Control Agency and used with subsets of the lake data base to explore acid-loading lake response relationships. Significant relationships were found between ASO4. and precipitation acidity (H+p ) but not between AAlk and H+n for all lakes in the region. A weighted regression procedure showed that- H+p had significant relationships with boch ASO4 and AAlk for seepage lakes,however, and these relationships were used to develop estimates of acid loading criteria designed to prevent the acidificacion of the most acid-sensitive lakes in each state. The critical H+p loading value estimated this way for Minnesota lakes is about 11 kg/ha-yr. A model to predict in-lake alkalinity generation (IAG) was developed based on CSTR (continuous-flow stirred reactor) kinetics. The model describes budgets for each ion involved in alkalinity regulation by a differential equation that includes terms for inputs and outputs and a first-order source/sink term. The equations are linked to an alkalinity balance equation that includes inputs, outputs, IAG by sulfate and nitrate reduction, and internal alkalinity consumption by ammonium assimilation. Calibration of the model was accomplished using ion budget data obtained from studies on 14 softwater lakes in diverse geographic areas. Rate coefficients generally are similar among softwater lakes: kSO4,, = 0.5 m/yr; kNO3.= 1.3 yr-1; kNH4 + = 1.5 yr.-t. Sensitivity analysis showed that predicted alkalinity is sensitive to water residence times but not very sensitive to moderate changes in rate coefficient values. According to the model, IAG is important in regulating the alkalinity of lakes with water residence times greater than about 2 years. The model reflects the homeostatic nature of IAG: the process increases with increasing inputs of HNO3. or H2SO4 and decreases as loadings of these acids decrease.
  • Thumbnail Image
    Item
    MSRC2019: Mass, moisture, nitrogen, and phosphorus in street sweepings collected from five cities in the Twin Cities Metropolitan Area, Minnesota
    (2020-09-21) Hobbie, Sarah E.; Baker, Lawrence A.; Finlay, Jacques C.; shobbie@umn.edu; Hobbie, Sarah E; Departments of Ecology, Evolution & Behavior, and Bioproducts & Biosystems Engineering
    Quality of many urban water bodies is impaired because of phosphorus (P) loading from stormwater runoff. Trees near impervious surfaces contribute significantly to this P loading. Mounting evidence indicates that street sweeping, by removing nutrient-rich litterfall from streets, can effectively reduce inputs of pollutants to stormwater and reduce maintenance of downstream BMPs. Yet, street sweeping remains an underdeveloped BMP for P source reduction, as currently there is no easily implementable method for crediting sweeping practices that is approved by the Minnesota Pollution Control Agency (MPCA). Thus, water quality credits for street sweeping practices are typically not applied to permit conditions such as Total Maximum Daily Loads (TMDL) Waste Load Allocations in Minnesota. Through a UMN-MPCA-city partnership, we collected data on street sweeping loads including: sweeper volume, wet mass of solids, dry mass of solids, and nitrogen and phosphorus concentrations in sweepings and loads removed by different street sweeper types throughout the snow-free season (spring, summer, fall), across the range of tree canopy covers and species composition typical of Minnesota’s cities. Partner cities included Forest Lake, Minneapolis, Prior Lake, Roseville, and Shoreview.
  • Thumbnail Image
    Item
    Review of lake management in Minnesota
    (University of Minnesota, Water Resources Research Center, 1990-02) Baker, Lawrence A.; Swain, Edward B.
    Lake management practices in Minnesota included holistic Clean Lakes Projects, extensive remedial methods to control excessive phytoplankton and macrophyte growth, and fisheries improvement projects.