stream ecology (nr 280)
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
Stream Ecology (NR 280)
Chapter 2 – Stream flow
The Water Cycle and Water BalanceSimple Stream Hydraulics
Measuring Stream Velocity and DischargeSummarizing Stream Discharge
Earth’sWater
Saline(oceans)
97%
Fresh Water (3%) Other (0.9%)
Lakes(87%)
Surface Water (0.3%)Ground
Water(30.1%)
Ice Capsand
Glaciers(68.1%)
Swamps (11%)
Rivers (2%)
Fresh Water (All)
Fresh Water (Available)
Distribution of the Earth’s Water
If ~half of Ground Water is available, then maybe ~0.75% of Earth’s Water is “available”.
http://ga.water.usgs.gov/edu/waterdistribution.html
The Water Balance
Example Regional Water BalancesAllan and Castillo Fig 2.3
World Water Balance (inches per year)
Even at this gross level of aggregation, potential water resource problems are evident.
P = RO + Ev RO = ROGW + ROSW
Photos: UVM Landscape Change Program
Images from the 1927 Flood
Colchester, Rt 15 and Ft. Ethan Allan in foreground, right
Downtown MontpelierChamplain Mill, Winooski, city side
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
Runoff ProductionHorton overland flow (Robert E. Horton)
time
Infil
tratio
n ra
te, i
(mm
/hr)
Pre
cipi
tatio
n ra
te, p
(mm
/hr)
p > i overland flow
Runoff ProductionHorton Overland Flow
R5 Catchment, Oklahoma.Photo: K. Loague, Stanford Univ.
Kidsgeo.com
http://www.ceg.ncl.ac.uk/thefarm/
Runoff ProductionVariable Source Area model
(John D. Hewlett and later Thomas Dunne)
Ward & Trimble, Fig 5.3
Runoff ProductionVariable Source Area model
Source: Taiwan Forestry Research Institutehttp://oldpage.tfri.gov.tw/book/2000/23e.htm
Water flows downhill(…really, down potential)
ΔL
ΔH
ΔH/ΔL = hydraulic gradient, a “pushing” force that can do work
Velocity Profiles in a StreamVelocity is not uniform
Velocity
Dep
th (z
)
Velocity
Side View Plan View
0.2 * z
0.6 * z
0.8 * z
Dep
th (z
)
Wid
th (w
)W
idth
(w)Use 0.6*z for z<0.75m
Use mean of 0.2*z and 0.8*z for z>0.75m
Flow Dynamics
Source: USGS
Measuring Velocity• Floating object
- Requires a correction factor• Electromagnetic• Direct current• Acoustic Doppler, others• pubs
benmeadows.com
hachwater.comUSGS
sontekcom
oranges
rubber duckies
Measuring DischargeThe Velocity-Area Method
Q = Flow area * Flow velocity Q = Depth * Width * Velocity (Units: m*m*(m/s) = m3/sQ = Σ (Di x Wi x Vi), over many subsections, i = 1 to n
For example: 0.2 m * 0.34 m * .09 m/s = .006 m3/s
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.
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
Discharge Control Structures
V-notch weir Parshall flume
Weir and Flume Equations
C and k = f(θ)
Q = C hn where Q is in m3/s and h is in mCoefficiens C and n are computed as a function of “throat” width, b.
Rectangular weir
“V” notch weir
Source: http://www.lmnoeng.com/Weirs/
Discharge (Gaging) Stations
Mechanical Float and Recorder
Electronic pressure transducer and data logger
Telemetry
The Chezy, Manning, and Darcy-Wesibach Velocity Formulas
We will explore these more in lab
𝑉=𝐶√𝑅𝑆V=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
𝑉=1.49∗𝑅
23∗𝑆
12
𝑛 𝑉=√ 8𝑔𝑅𝑆𝑓
Modeling
HEC-RAS Modeling Software (US Army Corps of Engineers)http://www.hec.usace.army.mil/software/hec-ras/index.html
Area Specific Discharge
10 km2 watershed 2 km2 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
The HydrographSpecifically, a storm hydrograph
Ward & Trimble, Fig. 5.11
Surface Water Hydrograph
Seasonal Water Table Hydrograph
Short-Term Water Table Hydrograph
20-Jul-11 27-Jul-11 3-Aug-118.7
8.8
8.9
9
9.1
9.2
9.3
9.4
9.5
9.6
9.7
Pembroke NH Well Hydrograph (Blow Up)
Time (hourly data in July and August 2011)
Wat
er ta
ble
dept
h (fe
et)
Lake Level Hydrograph
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,
Impacts of Development on Stormwater Quantity
• Higher highs/lower lows• Intensification/flashiness• Flow regime modification
Time (hours)
Stre
am fl
ow (c
ubic
feet
per
sec
)
Rainfall
Runoff - developedRunoff - undeveloped
Runoff – “managed”
Effect of Stream Order on Hydrograph
Rainfall
1st Order
2nd Order
3rd Order
4th Order
As flow accumulates, resistance to flow causes the hydrograph to spread (dispersion) and the peak flow is increasingly delayed.
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 vs Pe
# Data for the following site(s) are contained in this file# USGS 04290500 WINOOSKI RIVER NEAR ESSEX JUNCTION, VT# -----------------------------------------------------------------------------------## agency_cdsite_no datetime cfs code5s 15s 16s 14s 14sUSGS 4290500 1/25/1929 920 AUSGS 4290500 1/26/1929 890 AUSGS 4290500 1/27/1929 990 AUSGS 4290500 1/28/1929 1150 AUSGS 4290500 1/29/1929 980 AUSGS 4290500 1/30/1929 840 AUSGS 4290500 1/31/1929 730 AUSGS 4290500 2/1/1929 700 AUSGS 4290500 2/2/1929 600 AUSGS 4290500 2/3/1929 450 AUSGS 4290500 2/4/1929 850 AUSGS 4290500 2/5/1929 880 AUSGS 4290500 2/6/1929 910 AUSGS 4290500 2/7/1929 650 AUSGS 4290500 2/8/1929 590 AUSGS 4290500 2/9/1929 500 A
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 vs Pe or RI
## U.S. Geological Survey# National Water Information System# Retrieved: 2011-09-04 23:57:41 EDT###agency_cdsite_no peak_dt peak_tm peak_va peak_cd gage_ht5s 15s 10d 6s 8s 27s 8sUSGS 4290500 11/4/1927 113000 7 50.4USGS 4290500 3/17/1929 19300 11.64USGS 4290500 1/9/1930 21300 12.6USGS 4290500 4/11/1931 22600 13.22USGS 4290500 4/13/1932 23600 13.68USGS 4290500 4/19/1933 34600 18.6USGS 4290500 4/13/1934 31600 17.32USGS 4290500 1/10/1935 30900 6 16.96USGS 4290500 3/19/1936 45300 6 23.54USGS 4290500 5/16/1937 26400 6 15.07USGS 4290500 9/22/1938 34300 6 18.72
Water Use in the US (2000)
Is it “small” or “large”?
What is “consumptive
use”?
Fig 1.8 in Ward and Trimble
We often ‘use’ water without realizing it
Miller (2004)Fig. 13.6, p. 298
1 automobile
1 kilogramcotton
1 kilogramaluminum
1 kilogramgrain-fed beef
1 kilogramrice
1 kilogramcorn
1 kilogrampaper
1 kilogramsteel
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)
We use more water than most
Environment Canada (http://www.ec.gc.ca/water/e_main.html)
The basic structure of waterThe water molecule is a “dipole”
Water as a Solvent
S. Berg, Winona College
What happens to the water we use?
Ward and Trimble Table 1.7
Where does the used water go?
Miller (2004)Fig. 19.5, p. 482
Discharge of untreatedmunicipal sewage
(nitrates and phosphates)Nitrogen compounds
produced by carsand factories
Discharge of treatedmunicipal sewage
(primary and secondarytreatment:
nitrates and phosphates)
Discharge of detergents
( phosphates)
Natural runoff(nitrates andphosphates
Manure runoffFrom feedlots(nitrates andPhosphates,
ammonia)
Dissolving of nitrogen oxides
(from internal combustionengines and furnaces)
Runoff and erosion(from from cultivation,mining, construction,
and poor land use)
Runoff from streets,lawns, and construction
lots (nitrates andphosphates)
Lake ecosystemnutrient overload
and breakdown of chemical cycling
Stormwater
Biological Condition(Phosphorus)
Biological Condition(Nitrogen)
Impaired Rivers
Burton and Pitt (2002) Stormwater Effects Handbook
Impaired Lakes
Burton and Pitt (2002) Stormwater Effects Handbook
Biological Condition(Taxa)
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