Stream Ecology (NR 280) Chapter 2 – Stream flow The Water Cycle and Water Balance Simple Stream...
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Stream Ecology (NR 280) Chapter 2 – Stream flow The Water Cycle and Water Balance Simple Stream Hydraulics Measuring Stream Velocity and Discharge Summarizing
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
Slide 2
Earths Water Saline (oceans) 97% Fresh Water (3%) Other (0.9%)
Lakes (87%) Surface Water (0.3%) Ground Water (30.1%) Ice Caps and
Glaciers (68.1%) Swamps (11%) Rivers (2%) Fresh Water (All) Fresh
Water (Available) Distribution of the Earths Water If ~half of
Ground Water is available, then maybe ~0.75% of Earths Water is
available. http://ga.water.usgs.gov/edu/waterdistribution.html
Slide 3
Slide 4
The Water Balance
Slide 5
Example Regional Water Balances Allan and Castillo Fig 2.3
Slide 6
World Water Balance (inches per year) Even at this gross level
of aggregation, potential water resource problems are evident. P =
RO + Ev RO = RO GW + RO SW
Slide 7
Photos: UVM Landscape Change Program Images from the 1927 Flood
Colchester, Rt 15 and Ft. Ethan Allan in foreground, right Downtown
Montpelier Champlain Mill, Winooski, city side
Runoff Production Horton overland flow (Robert E. Horton) time
Infiltration rate, i (mm/hr) Precipitation rate, p (mm/hr) p > i
overland flow
Slide 10
Runoff Production Horton Overland Flow R5 Catchment, Oklahoma.
Photo: K. Loague, Stanford Univ. Kidsgeo.com
http://www.ceg.ncl.ac.uk/thefarm/
Slide 11
Runoff Production Variable Source Area model (John D. Hewlett
and later Thomas Dunne) Ward & Trimble, Fig 5.3
Slide 12
Runoff Production Variable Source Area model Source: Taiwan
Forestry Research Institute
http://oldpage.tfri.gov.tw/book/2000/23e.htm
Slide 13
Gaining and Losing Streams Allan and Castillo Fig. 2.6
Slide 14
Geochemical indicators of runoff production Source: Burns et
al., 2001. Quantifying contributions to storm runoff through end-
member mixing analysis and hydrologic measurements at the Panola
Mountain Research Watershed (Georgia, USA). Hydrol. Process. 15,
19031924 (2001)
Slide 15
Water flows downhill (really, down potential) LL HH H/L =
hydraulic gradient, a pushing force that can do work
Slide 16
Water flows downhill (and through the substrate if possible)
L1L1 H3H3 The hyporheic zone L2L2 L3L3 H2H2 H1H1
Slide 17
Velocity Profiles in a Stream Velocity is not uniform Velocity
Depth (z) Velocity Side ViewPlan View 0.2 * z 0.6 * z 0.8 * z Depth
(z) Width (w) Use 0.6*z for z0.75m
Slide 18
Flow Dynamics Source: USGS
Slide 19
Measuring Velocity Floating object - Requires a correction
factor Electromagnetic Direct current Acoustic Doppler, others pubs
benmeadows.com hachwater.com USGS sontekcom oranges rubber
duckies
Slide 20
Measuring Discharge The Velocity-Area Method Q = Flow area *
Flow velocity Q = Depth * Width * Velocity (Units: m*m*(m/s) = m 3
/s Q = (D i x W i x V i ), over many subsections, i = 1 to n For
example: 0.2 m * 0.34 m *.09 m/s =.006 m 3 /s
Slide 21
Measuring Discharge Images: U.S. Geological Survey 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.
Slide 22
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
Slide 23
Discharge Control Structures V-notch weirParshall flume
Slide 24
Weir and Flume Equations C and k = f() Q = C h n where Q is in
m 3 /s and h is in m Coefficiens C and n are computed as a function
of throat width, b. Rectangular weir V notch weir Source:
http://www.lmnoeng.com/Weirs/
Slide 25
Discharge (Gaging) Stations Mechanical Float and Recorder
Electronic pressure transducer and data logger Telemetry
Slide 26
The Chezy, Manning, and Darcy-Wesibach Velocity Formulas We
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 = Mannings Coefficient g = acceleration of gravity
(constant) f = Darcy-Weisbach Friction Factor
Slide 27
Modeling HEC-RAS Modeling Software (US Army Corps of Engineers)
http://www.hec.usace.army.mil/software/hec-ras/index.html
Slide 28
Area Specific Discharge 10 km 2 watershed2 km 2 watershed Avg.
Flow = 17 m 3 s -1 / 10 km 2 = 1.7 m 3 s -1 / km 2 = 14.7 cm d -1
Avg. Flow = 3 m 3 s -1 / 2 km 2 = 1.5 m 3 s -1 / km 2 = 12.6 cm d
-1
Slide 29
The Hydrograph Specifically, a storm hydrograph Ward &
Trimble, Fig. 5.11
Slide 30
Surface Water Hydrograph
Slide 31
Seasonal Water Table Hydrograph
Slide 32
Short-Term Water Table Hydrograph
Slide 33
Lake Level Hydrograph
Slide 34
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,
Slide 35
Impacts of Development on Stormwater Quantity Higher
highs/lower lows Intensification/flashiness Flow regime
modification Time (hours) Stream flow (cubic feet per sec) Rainfall
Runoff - developed Runoff - undeveloped Runoff managed
Slide 36
Effect of Stream Order on Hydrograph Rainfall 1 st Order 2 nd
Order 3 rd Order 4 th Order As flow accumulates, resistance to flow
causes the hydrograph to spread (dispersion) and the peak flow is
increasingly delayed.
Slide 37
Flow (Anything) Duration Obtain data series (Any regular
series) Rank in descending order (Regardless of date) Probability
of Exceedence P e = (rank#)/(max. rank + 1) Plot data vs P e
Slide 38
Extreme Events The Annual Maximum Series Obtain data series
(Annual Maximum only) Rank in descending order (Regardless of year)
Probability of Exceedence P e = (rank#)/(max. rank + 1) Return
interval is RI = 1/P e Plot data vs P e or RI
Slide 39
Water Use in the US (2000) Is it small or large? What is
consumptive use? Fig 1.8 in Ward and Trimble
Slide 40
We often use water without realizing it Miller (2004) Fig.
13.6, p. 298 1 automobile 1 kilogram cotton 1 kilogram aluminum 1
kilogram grain-fed beef 1 kilogram rice 1 kilogram corn 1 kilogram
paper 1 kilogram steel 400,000 liters (106,000 gallons) 10,500
liters (2,400 gallons) 9,000 liters (2,800 gallons) 7,000 liters
(1,900 gallons) 5,000 liters (1,300 gallons) 1,500 liters (400
gallons) 880 liters (230 gallons) 220 liters (60 gallons)
Slide 41
We use more water than most Environment Canada
(http://www.ec.gc.ca/water/e_main.html)
Slide 42
The basic structure of water The water molecule is a
dipole
Slide 43
Water as a Solvent S. Berg, Winona College
Slide 44
What happens to the water we use? Ward and Trimble Table
1.7
Slide 45
Where does the used water go? Miller (2004) Fig. 19.5, p. 482
Discharge of untreated municipal sewage (nitrates and phosphates)
Nitrogen compounds produced by cars and factories Discharge of
treated municipal sewage (primary and secondary treatment: nitrates
and phosphates) Discharge of detergents ( phosphates) Natural
runoff (nitrates and phosphates Manure runoff From feedlots
(nitrates and Phosphates, ammonia) Dissolving of nitrogen oxides
(from internal combustion engines and furnaces) Runoff and erosion
(from from cultivation, mining, construction, and poor land use)
Runoff from streets, lawns, and construction lots (nitrates and
phosphates) Lake ecosystem nutrient overload and breakdown of
chemical cycling Stormwater
Slide 46
Biological Condition (Phosphorus)
Slide 47
Biological Condition (Nitrogen)
Slide 48
Impaired Rivers Burton and Pitt (2002) Stormwater Effects
Handbook
Slide 49
Impaired Lakes Burton and Pitt (2002) Stormwater Effects
Handbook
Slide 50
Biological Condition (Taxa)
Slide 51
Why should we care? Drinking water Irrigation Contact
(swimming, wading) Recreation (fishing, boating) Waste purification
Aesthetics Ecosystem integrity Friday, August 6, 2004 U.S. beach
closures hit 14- year high - Unsafe water caused by runoff, lack of
funding, report says Credit: Center for Watershed Protection