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Stream Ecology (NR 280)

Stream Ecology (NR 280). Chapter 2 – Stream flow The Water Cycle and Water Balance Simple Stream Hydraulics Measuring Stream Velocity and Discharge Summarizing Stream Discharge. Fresh Water (3%). Other (0.9%). Rivers (2%). Surface Water (0.3%). Swamps (11%). Ground Water

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Stream Ecology (NR 280)

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  1. Stream Ecology (NR 280) Chapter 2 – Stream flow The Water Cycle and Water Balance Simple Stream Hydraulics Measuring Stream Velocity and Discharge Summarizing Stream Discharge

  2. Fresh Water (3%) Other (0.9%) Rivers (2%) Surface Water (0.3%) Swamps (11%) Ground Water (30.1%) Saline (oceans) 97% Ice Caps and Glaciers (68.1%) Lakes (87%) Fresh Water (All) Fresh Water (Available) Earth’s Water Distribution of the Earth’s Water http://ga.water.usgs.gov/edu/waterdistribution.html If ~half of Ground Water is available, then maybe ~0.75% of Earth’s Water is “available”.

  3. The Water Balance

  4. Example Regional Water BalancesAllan and Castillo Fig 2.3

  5. World Water Balance (inches per year) P = RO + Ev RO = ROGW + ROSW Even at this gross level of aggregation, potential water resource problems are evident.

  6. Images from the 1927 Flood Colchester, Rt 15 and Ft. Ethan Allan in foreground, right Downtown Montpelier Champlain Mill, Winooski, city side Photos: UVM Landscape Change Program

  7. Why predict runoff? • Estimate water supply (seasonal, annual) • Estimate flood hazard, flood flows (event-based) • Design infrastructure – detention basins, culvert sizing (“design storm”) • Understand system behavior

  8. Precipitation rate, p (mm/hr) Runoff ProductionHorton overland flow (Robert E. Horton) p > i  overland flow Infiltration rate, i (mm/hr) time

  9. Runoff ProductionHorton Overland Flow http://www.ceg.ncl.ac.uk/thefarm/ Kidsgeo.com R5 Catchment, Oklahoma. Photo: K. Loague, Stanford Univ.

  10. Runoff ProductionVariable Source Area model(John D. Hewlett and later Thomas Dunne) Ward & Trimble, Fig 5.3

  11. Runoff ProductionVariable Source Area model Source: Taiwan Forestry Research Institute http://oldpage.tfri.gov.tw/book/2000/23e.htm

  12. Water flows downhill(…really, down potential) ΔL ΔH ΔH/ΔL = hydraulic gradient, a “pushing” force that can do work

  13. Velocity Profiles in a StreamVelocity is not uniform Side View Plan View 0.2 * z Depth (z) Width (w) 0.6 * z 0.8 * z Velocity Velocity Use 0.6*z for z<0.75m Use mean of 0.2*z and 0.8*z for z>0.75m Depth (z) Width (w)

  14. Flow Dynamics Source: USGS

  15. Measuring Velocity • Floating object • - Requires a correction factor • Electromagnetic • Direct current • Acoustic Doppler, others • pubs oranges rubber duckies sontekcom benmeadows.com USGS hachwater.com

  16. Measuring DischargeThe Velocity-Area Method Q = Flow area * Flow velocity Q = Depth * Width * Velocity (Units: m*m*(m/s) = m3/s Q = Σ (Dix Wix Vi), over many subsections, i = 1 to n For example: 0.2 m * 0.34 m * .09 m/s = .006 m3/s

  17. Measuring Discharge • Obtain Q measurements at various stages • Relate to Q to stage • Fit a line or curve (may take multiple fits) • Apply equation to past or future stage measurements • Assumes relation between Q and stage remains constant • Labor intensive and therefore expensive. Subject to change. Images: U.S. Geological Survey

  18. Challenges • Taking measurements in the exactly the same spot is difficult • The velocity-area method is time consuming • If the channel shape at the “control section” changes, so does the rating curve tfhrc.gov tfhrc.govusace.army.gov

  19. Discharge Control Structures V-notch weir Parshall flume

  20. Weir and Flume Equations Rectangular weir “V” notch weir C and k = f(θ) Q = C hn where Q is in m3/s and h is in m Coefficiens C and n are computed as a function of “throat” width, b. Source: http://www.lmnoeng.com/Weirs/

  21. Discharge (Gaging) Stations Telemetry Electronic pressure transducer and data logger Mechanical Float and Recorder

  22. The Chezy, Manning, and Darcy-Wesibach Velocity FormulasWe will explore these more in lab V=Velocity (L/T) C=Chezy Friction Coefficient (L1/2/T) R = Hydraulic Radius (L) S = Slope (L/L, dimensionless) n = Manning’s Coefficient g = acceleration of gravity (constant) f = Darcy-Weisbach Friction Factor

  23. Modeling HEC-RAS Modeling Software (US Army Corps of Engineers) http://www.hec.usace.army.mil/software/hec-ras/index.html

  24. Area Specific Discharge 10 km2 watershed 2km2 watershed Avg. Flow = 17 m3s-1 / 10 km2 = 1.7 m3s-1/ km2 = 14.7 cm d-1 Avg. Flow = 3 m3s-1/ 2 km2 = 1.5 m3s-1/ km2 = 12.6 cm d-1

  25. The HydrographSpecifically, a storm hydrograph Ward & Trimble, Fig. 5.11

  26. Surface Water Hydrograph

  27. Seasonal Water Table Hydrograph

  28. Short-Term Water Table Hydrograph

  29. Lake Level Hydrograph

  30. Factors affecting runoff • Precipitation- • Type, duration, amount, intensity • Watershed Characteristics • Size, topography, shape, orientation, geology, soils • Land Cover and Land Use • Forestry, wetlands, agricultural, urban density, impervious area,

  31. Rainfall Runoff - undeveloped Runoff - developed Runoff – “managed” Impacts of Development on StormwaterQuantity • Higher highs/lower lows • Intensification/flashiness • Flow regime modification Stream flow (cubic feet per sec) Time (hours)

  32. Effect of Stream Order on Hydrograph As flow accumulates, resistance to flow causes the hydrograph to spread (dispersion) and the peak flow is increasingly delayed. Rainfall 1st Order 2nd Order 3rd Order 4th Order

  33. Flow (Anything) Duration • Obtain data series(Any regular series) • Rank in descending order(Regardless of date) • Probability of ExceedencePe = (rank#)/(max. rank + 1) • Plot data vsPe

  34. Extreme EventsThe “Annual Maximum Series” • Obtain data series(Annual Maximum only) • Rank in descending order(Regardless of year) • Probability of ExceedencePe = (rank#)/(max. rank + 1) • Return interval isRI = 1/Pe • Plot data vsPe or RI

  35. What is “consumptive use”? Water Use in the US (2000) Is it “small” or “large”? Fig 1.8 in Ward and Trimble

  36. 1 automobile 400,000 liters (106,000 gallons) 1 kilogram cotton 10,500 liters (2,400 gallons) 1 kilogram aluminum 9,000 liters (2,800 gallons) 1 kilogram grain-fed beef 7,000 liters (1,900 gallons) 1 kilogram rice 5,000 liters (1,300 gallons) 1 kilogram corn 1,500 liters (400 gallons) 1 kilogram paper 880 liters (230 gallons) 1 kilogram steel Miller (2004) Fig. 13.6, p. 298 220 liters (60 gallons) We often ‘use’ water without realizing it

  37. We use more water than most Environment Canada (http://www.ec.gc.ca/water/e_main.html)

  38. The basic structure of waterThe water molecule is a “dipole”

  39. Water as a Solvent S. Berg, Winona College

  40. What happens to the water we use? Ward and Trimble Table 1.7

  41. Discharge of untreated municipal sewage (nitrates and phosphates) Nitrogen compounds produced by cars and factories Natural runoff (nitrates and phosphates Discharge of detergents ( phosphates) Manure runoff From feedlots (nitrates and Phosphates, ammonia) Discharge of treated municipal sewage (primary and secondary treatment: nitrates and phosphates) Runoff from streets, lawns, and construction lots (nitrates and phosphates) Lake ecosystem nutrient overload and breakdown of chemical cycling Runoff and erosion (from from cultivation, mining, construction, and poor land use) Dissolving of nitrogen oxides (from internal combustion engines and furnaces) Miller (2004) Fig. 19.5, p. 482 Where does the used water go? Stormwater

  42. Biological Condition(Phosphorus)

  43. Biological Condition(Nitrogen)

  44. Impaired Rivers Burton and Pitt (2002) Stormwater Effects Handbook

  45. Impaired Lakes Burton and Pitt (2002) Stormwater Effects Handbook

  46. Biological Condition(Taxa)

  47. Why should we care? Friday, August 6, 2004 “U.S. beach closures hit 14-year high - Unsafe water caused by runoff, lack of funding, report says” • Drinking water • Irrigation • Contact (swimming, wading) • Recreation (fishing, boating) • Waste purification • Aesthetics • Ecosystem integrity Credit: Center for Watershed Protection

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