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

Earth’s 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 Earth’s Water If ~half of Ground Water is available, then maybe ~0.75% of Earth’s Water is “available”.

The Water Balance

Example Regional Water Balances Allan 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 = RO GW + RO SW

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

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

Runoff Production Horton Overland Flow R5 Catchment, Oklahoma. Photo: K. Loague, Stanford Univ. Kidsgeo.com

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

Runoff Production Variable Source Area model Source: Taiwan Forestry Research Institute

Gaining and Losing Streams Allan and Castillo Fig. 2.6

Geochemical indicators of runoff production Source: Burns et al., Quantifying contributions to storm runoff through end- member mixing analysis and hydrologic measurements at the Panola Mountain Research Watershed (Georgia, USA). Hydrol. Process. 15, 1903–1924 (2001)

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

Water flows downhill (…and through the substrate if possible) ΔL1ΔL1 ΔH3ΔH3 The hyporheic zone ΔL2ΔL2 ΔL3ΔL3 ΔH2ΔH2 ΔH1ΔH1

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 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.com USGS sontekcom oranges rubber duckies

Measuring Discharge The Velocity-Area Method Q = Flow area * Flow velocity Q = Depth * Width * Velocity (Units: m*m*(m/s) = m 3 /s Q = Σ (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

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 weirParshall flume

Weir and Flume Equations C and k = f(θ) 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:

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=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

Modeling HEC-RAS Modeling Software (US Army Corps of Engineers)

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

The Hydrograph Specifically, a storm hydrograph Ward & Trimble, Fig. 5.11

Surface Water Hydrograph

Seasonal Water Table Hydrograph

Short-Term Water Table Hydrograph

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) Stream flow (cubic feet per sec) Rainfall Runoff - developed Runoff - undeveloped Runoff – “managed”

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.

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

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

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 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)

We use more water than most Environment Canada (

The basic structure of water The 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 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

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