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Chapter 15

Chapter 15. Issues in Water Quality. What is Water Quality? . Physical Sufficient flow to sustain fish and aquatics Enough pools and riffles Riparian zone for woody debris Chemical Enough nutrients for primary production Not too much nutrients or contaminants Biological

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Chapter 15

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  1. Chapter 15 Issues in Water Quality

  2. What is Water Quality? • Physical • Sufficient flow to sustain fish and aquatics • Enough pools and riffles • Riparian zone for woody debris • Chemical • Enough nutrients for primary production • Not too much nutrients or contaminants • Biological • No exotics plants or animals • No harmful diseases

  3. Water Quality Laws • Clean Water Act • Regulates discharges • Point Sources: Wastewater Treatment Plants • Nonpoint Sources: Agriculture, Forestry • Safe Drinking Water Act • Regulates water supplies • Groundwater => Wellhead protection zones • Surface Water => Source Water Assessments

  4. Water Resource and Landscape Issues • Water Quality • Overland flow causes rill and gully erosion • Soils have a strong influence on the chemical composition of water entering streams and wetlands. • Soils also influence the suitability of groundwater for drinking water.

  5. Floods & Baseflows • Soil and vegetative conditions determine how rainfall moves to streams and thus affect baseflows and flood peaks and volumes. • Site Productivity • Soil moisture limits tree and crop growth in much of the US. Some parts of the landscape grow trees or crop better because topographic and geologic conditions cause water to accumulate in those areas. • But subsurface flows may make an area too wet to grow crops.

  6. Stormwater Management • Hydrologic alteration by development depends on the degree to which soils are disturbed, vegetation is altered, and land is covered with pavement. • Appropriate design of stormwater management and treatment facilities is needed to minimize this change. • Hillslope Stability • Landslides are largely driven by subsurface flow conditions. • Seepage areas on steep hillslopes are high landslide danger areas.

  7. Stream, Slope, and Wetland Geomorphology • Geologic conditions control hydrologic processes - but runoff patterns and characteristics alter the landscape. • Runoff and groundwater flow affect streams and wetlands as well as other landscape features. • Landscapes are never in equilibrium, but some landscapes change much more rapidly than others.

  8. Landscape Factors Controlling Hydrologic Characteristics • Climate • Cyclonic fronts, thunderstorms, monsoons, ... • Seasonality of precipitation • Precipitation Type - rain, snow, rain-on-snow • Temperature - Humidity - ET regimes

  9. Soils and Geology • Depth of soils • Soil layering • Infiltration rates • Hydraulic conductivities • Soil moisture characteristic curves • Topography • Slopes of ground surface • Presence and abundance of wetlands and lakes (also related to geology, soils, and climate) • Valley morphology (floodplain storage)

  10. Vegetation • Interception • Macropore development • Evapotranspiration • Development of humus layer • Soil organic content

  11. Forest Management • Forest streams have less stormflow and total flow • Forest litter (O-Horizon) increases infiltration • Forest canopies intercept more precipitation (higher LAI) • Forest have higher evapotranspiration rates • Forest soils dry faster, have higher total storage

  12. Best Management Practices, BMPs • Used to improve soil and water quality • Harvesting • High-lead yarding on steep slopes reduces soil compaction • Soft tires reduces soil compaction • Water is filtered using vegetated stream buffers (SMZs) • Water temperatures also affected by buffers

  13. High Lead Logging

  14. Roads • Road runoff can be dispersed onto planar and convex slopes • Broad-based dips can prevent road erosion

  15. Broad-Based Dips

  16. Road Construction

  17. Roadbed Construction

  18. Site Preparation • Burning a site increases soil erosion and reduces infiltration • Leaving mulch on soils increases infiltration • Piling mulch concentrates nutrients into local hot spots • Distributing mulch returns nutrients to soils • Some herbicides cause nitrate increase in streams

  19. Agricultural Land Management • Overland flow is a main concern in agriculture • increases soil erosion, nutrients, and fecal coliform increases herbicides, pesticides, rodenticides, fungicides • Plowing • exposes the soil surface to rainfall (and wind) forces • mulching and no-till reduces runoff and increases infiltration • terracing and contour plowing also helps

  20. Pastures (livestock grazing) • increases soil compaction • reduces vegetative plant cover • increases bank erosion • rotating cattle between pastures and fencing streams reduce problems

  21. Urban Land Management • Urban lands have more impervious surfaces • More runoff, less infiltration, recharge, and baseflow • Very high peak discharges, pollutant loads • Less soil storage, channels are straightened and piped, no floodplains • Baseflows are generally lower, except for irrigation water (lawns & septic)

  22. Atlanta, Georgia “the fastest-spreading human settlement in history" Time Magazine March 22, 1999

  23. Ag/Poultry Forests Gainesville Lake Lanier Buford Dam

  24. Vegetated Swales

  25. Drywell

  26. Chap 15 Quiz Georgia now manages water quality using a watershed perspective. Does this mean: 1. (True / False) Point sources are permitted without consideration of other dischargers. 2. (True / False) Point sources increase nonpoint sources of pollution 3. (True / False) All nonpoint sources must now be permitted 4. Best Management Practices (BMPs) are now required for: (True / False) forestry (True / False) agriculture (True / False) construction (True / False) homes and businesses

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