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Urban Streams Characteristics Study: Denver, Colorado

Explore impacts of urbanization on hydrology, ecology, and chemistry of streams near Denver, CO. Investigate key stressors and environmental responses. Compare findings across varied settings.

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Urban Streams Characteristics Study: Denver, Colorado

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  1. Physical, chemical, and biological characteristics of streams in urbanizing areas near Denver, Colorado Lori Sprague Robert Zuellig Hydrologist Ecologist U.S. Geological Survey Denver, CO May 2006 U.S. Department of the Interior U.S. Geological Survey

  2. Study Objectives • Determine the effects of urbanization on hydrologic, geomorphic, chemical, habitat, and biological conditions • Determine the most important urban stressors related to the responses • Compare these responses over a range of environmental settings throughout the Nation

  3. Wyoming Nebraska Colorado Population in the South Platte River Basin increased by about 670,000 people from 1990 through 2000, to over 2.8 million Denver

  4. South Boulder Creek 1987 South Boulder Creek 1937 Photos courtesy of USFS http://bcn.boulder.co.us/basin/gallery/sboulder50yrs.html

  5. Water management Photos from http://bcn.boulder.co.us/basin/gallery

  6. Site Selection • Environmental characteristics – homogeneous environmental framework controlled for “natural” sources of variability • Urban intensity – sites represented a gradient of urbanization (urban intensity index)

  7. North Platte Cheyenne Julesburg Sterling Fort Collins Estes Park Greeley Loveland Kersey Fort Morgan Henderson Boulder Idaho Springs Denver Parker Wyoming Nebraska Castle Rock 0 20 40 km Colorado

  8. Stream with high-level urban intensity Urban Intensity Index = 100

  9. Stream with mid-level urban intensity Urban Intensity Index = 40

  10. Stream with low-level urban intensity Urban Intensity Index = 3

  11. Study Design • Chemical characteristics nutrients, pesticides, sediment, chloride, sulfate, bacteria (spring and summer base flow) • Biological characteristics algae, invertebrates, fish (summer low flow) • Physical characteristics habitat (summer low flow), streamflow, water temperature (continuous for 1 year)

  12. Time and flow integrated chemical parameters • Semi-permeable membrane devices (SPMDs) • Placed at all 28 sites for 4 weeks • Sequesters hydrophobic organics • Mimics bioaccumulation in fish

  13. Non-native species Flashier streams, higher peak flows Pollutant generation, higher concentrations Channelization, riparian clearing Greater extremes, more fluctuation Conceptual model Fish Algae Invertebrates Chemistry Hydrology Habitat Temperature Urbanization

  14. Sediment Sulfate • Base-flow chemistry • Suspended sediment related to housing age • Sulfate related to population density Housing age Population density Fish Algae Invertebrates Chemistry Hydrology Habitat Temperature Urbanization

  15. Fish Algae Invertebrates PAHs • SPMD chemistry • PAHs related to stream flashiness and many measures of urbanization • Variability in PAHs best explained by distance from stream to nearest road Flashiness Chemistry Hydrology Temperature Habitat Land cover Road density Housing age Housing density Population density Urban intensity index Urbanization

  16. Fish Algae Invertebrates Sediment Sulfate PAHs Flashiness Chemistry Urbanization explained variability of SPMD chemistry well, but not variability of spring and summer base-flow chemistry Hydrology Temperature Habitat Land cover Road density Housing age Housing density Population density Urban intensity index Urbanization

  17. Fish Algae Invertebrates Hydrology No strong relations between hydrology and urbanization Chemistry Hydrology Habitat No strong relations between habitat and urbanization Temperature Habitat Urbanization

  18. Fish Algae Invertebrates Chemistry Water temperature Temperatures related to high-intensity development near the stream Hydrology Duration of falling temperatures Temperature Habitat Land cover Urbanization

  19. Fish Algae Invertebrates Sediment Chloride Chemistry Hydrology Fish communities were related predominantly to housing age, fine suspended sediment, and chloride Habitat Temperature Housing age Urbanization

  20. Fish Algae Invertebrates Conductivity Nutrients Pesticides Duration of high flows Flashiness Chemistry Hydrology Algal biomass was related predominantly to conductivity, nutrients, pesticides, the duration of high flows, and stream flashiness Habitat Temperature Urbanization

  21. Fish Algae Invertebrates Nutrients Pesticides Duration of high flows Flashiness Chemistry Hydrology Invertebrate communities were related predominantly to nutrients, pesticides, duration of high flows, and stream flashiness Habitat Temperature Urbanization

  22. ? Water management Other Factors Fish Algae Invertebrates Sediment Sulfate Chloride Conductivity Nutrients Pesticides PAHs Duration of high flows Flashiness Chemistry Hydrology Aquatic communities were related to chemistry and hydrology, but chemistry and hydrology generally were not strongly related to urbanization Duration of falling temperatures Habitat Temperature Land cover Road density Housing age Housing density Population density Urban intensity index Urbanization

  23. Comparison – Total Pesticide Concentration 2.5 Raleigh 2.0 Portland 1.5 Concentration, μg/L Atlanta 1.0 Denver 0.5 0.0 0 20 40 60 80 100 0.25 Urban Intensity Index 0.20 0.15 Concentration, μg/L 0.10 0.05 0.00 0 20 40 60 80 100 Urban Intensity Index

  24. Comparison – EPT Richness Comparison – EPT Richness 35 30 25 20 EPT Richness 15 10 Denver 5 0 0 20 40 60 80 100 16 Urban Intensity Index 12 8 EPT Richness 4 0 0 20 40 60 80 100 Urban Intensity Index 35 30 Raleigh 25 Portland 20 EPT Richness Atlanta 15 10 5 0 0 20 40 60 80 100 Urban Intensity Index

  25. Conclusions • Aquatic communities were related to chemistry and hydrology, but chemistry and hydrology generally were not strongly related to urbanization • Commonly observed effects of urbanization (stream flashiness, increased chemical concentrations, fewer sensitive species) were not observed • Present-day aquatic communities are tolerant even in areas with minimal development • Water management? • Does not mean urbanization is not affecting stream ecosystems • Likely multiple interacting stressors, including urbanization • Protection of stream ecosystems may need to involve numerous strategies

  26. CONTACT INFORMATION Lori Sprague Robert Zuellig lsprague@usgs.gov rzuellig@usgs.gov 303-236-4882 x262 303-236-4882 x278 U.S. Geological Survey Colorado Water Science Center Denver Federal Center Building 53 MS 415 Denver, CO 80225

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