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