Streamflow and hydrograph learning objectives 1.Learn where to find electronic hydrology data and download it 2.Learn how to interpret hydrographs 3.Understand.

Streamflow and hydrograph learning objectives

1. Learn where to find electronic hydrology data and download it

2. Learn how to interpret hydrographs

3. Understand flood frequency terms and methods including binomial risk assessment

4. Understand watershed terminology

5. Learn how to use Manning’s equation and understand variables that go into it

6. Understand the continuity equation for streamflow

7. Learn how to measure velocity and compute discharge

http://www.uwsp.edu/geo/faculty/lemke/geomorphology/lecture_outlines/02_runoff_generation.html

RUNOFF

• Component of hydrologic cycle

• 3 generally acknowledge methods of generation of runoff– Hortonian overland flow (surface runoff)– Shallow subsurface runoff – Saturated overland flow (return flow)

Types of Runoff Generation

Ground water

i > f Hortonian Overland Flow

Ground water

Saturated soil Saturated overlandflow

Shallow subsurface flow

Sandy loamClay loam

Ground water

Partial Area Runoff

Sandy loam

Ground water

http://www.uwsp.edu/geo/faculty/lemke/geomorphology/lecture_outlines/02_runoff_generation.html

10 m10 m

10 m 10 m

February 2003

July 2003

August 2003 September 2003

Figure 7. Schematic of lateral contraction of surface water expression observed around channel heads in stream at RotTags.

What is a watershed?

• The land area that drains into a selected stream or water body

• Can by very small or very large

• Called catchments in the rest of the world

• Usually based on surface topography- subsurface features may not mimic surface ones as far as drainage is concerned

Watershed areas

• Area is a basic piece of information that one needs for many purposes, e.g.,– Trees /area– Runoff / area– Soil nutrients / area– Watershed area defines the area that delivers

water, sediment and nutrients to a water body

Graphic method of measuring areaCount the vertices within the area

• Each vertix represents the center of the area around it

Scale 51 vertices

Graphic method for area

• Trace your watershed on vellum or other transparent paper

• Lay the area over gridded graph paper• Count the number of vertices• Use the scale on your map to figure out how

much area one square of your graph paper represents

• Multiple the area of one square by the number of vertices you counted

Who measures water and watersheds?

USGS- US Geological SurveyUSBoR – US Bureau of ReclamationUSACOE – US Army Corp of EngineersUSFS – US Forest ServiceNRCS – National Resources Conservation ServiceUSEPA – US Environmental Protection AgencyUSFWS – US Fish and Wildlife ServiceNOAA – National Oceanic and Atmospheric AdministrationNMFS – National Marine Fisheries ServiceTRIBESCities, counties, states, schools

• Watershed data– EPA Surf your watershed

http://www.epa.gov/surf/

• Climate data (national and international)http://www.ncdc.noaa.gov/oa/ncdc.html

Washington http://www.wrcc.dri.edu/summary/climsmwa.html

Examples of where to locate national data for watersheds and streams

• Stream data- quantity and quality– USGS Water Resources Data

http://water.usgs.gov/data.html

• Soils data– http://soils.usda.gov/

• Aquatic biologic indicators– http://www.epa.gov/bioindicators/

Examples of where to locate national data for watersheds and streams

Runoff

Precipitation

Topography

Basin size

Basin shape

Soils

Geology

Land cover/land use

Aspect

Factors affecting runoff

Factors Affecting Runoff

• Precipitation-– Type– Duration– Amount– Intensity– Design storm event– Direction of movement – Extent

Watershed Factors that Affect Runoff

• Size- area of watershed

• Topography – slope of watershed

• Shape of watershed

• Aspect of watershed

• Geology

• Soil

• Land cover

Effect of watershed area• 1mm of rain on 1km2 of watershed represents an input of 1,000 m3

of water or about 250,000 gallons of water.

• If you prefer, 1inch of water on a 1mile2 watershed represents an input of 17 million gallons of water.

• If a watershed, of 11 mile2 receives an annual precipitation of 40 inches, that is about 7.6 billion gallons of water each year or just over 1 billion ft3.

• If just 15% ran off, this would be an average discharge of 4.8 cfs.

Watershed Factors that Affect Runoff

• Size- area of watershed• Topography – slope of watershed

– May include drainage density effects

• Shape of watershed• Aspect of watershed• Geology• Soil• Land cover

Topography and drainage density

• Slope affects stream velocity

• Drainage density affects travel time of precipitation to channel

Watershed Factors that Affect Runoff

• Size- area of watershed• Topography – slope of watershed

– May include drainage density effects

• Shape of watershed• Aspect of watershed• Geology• Soil• Land cover

Effects of watershed shape on runoff

Higher runoff ratesMore likely to reach outlet at same time

Elevated rates may persist longeras runoff from upstream continues toarrive downstream

Watershed Factors that Affect Runoff

• Size- area of watershed• Topography – slope of watershed

– May include drainage density effects

• Shape of watershed• Aspect of watershed• Geology• Soil• Land cover

Effects of watershed aspect on runoff

• Aspect is the compass direction that the slope of the watershed faces

• Often minimized by variety and complexity of aspects throughout watershed

• Can affect air, water and soil temperature and therefore snowmelt rates and ET rates– And vegetation communities

Watershed Factors that Affect Runoff

• Size- area of watershed• Topography – slope of watershed

– May include drainage density effects

• Shape of watershed• Aspect of watershed• Geology• Soil• Land cover

Effects of watershed geology and soil on runoff

• Geology affects depth to bedrock

• Affects fracture rates and porosity of bedrock

• Geology affects soil properties such as texture and porosity which affect infiltration rates

• Geology affects groundwater divides and thus baseflow delivery

• Antecedent soil moisture level

Watershed Factors that Affect Runoff

• Size- area of watershed• Topography – slope of watershed

– May include drainage density effects

• Shape of watershed• Aspect of watershed• Geology• Soil• Land cover

Land cover effects on runoff

• ?

Hydrographs

• Hydrographs depict water amount over time

• Integrate the watershed response to precipitation

• Units may be – stage (depth of water) in channel – discharge (volumetric rate) – depth of runoff (volume in channel / area of

watershed)

Fig. 5.1

Fig. 5.3

Fig. 5.13

Fig. 5.14

Hydrographs

• Can depict an event

• Can depict a season or year

• Can depict longer periods

http://www.nwd-wc.usace.army.mil/nws/hh/basins/lwscsh.html

Hourly data

Daily stream discharge for January 2004

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Mercer Creek- Average January Discharge in cfs

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Peak Flow (cfs) Mercer Creek

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USGS estimate of onsetof urbanization effects

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Chehalis River- Average monthly discharge (cfs) 1992-2004 Water Years

Cjhehalis River WY 2004

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Chewuch River near Winthrop

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Esquatzel Coulee

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Water year 2004

http://biology.queensu.ca/~bio111/pdf%20files/lect4-biogeochemistry.PDF

http://biology.queensu.ca/~bio111/pdf%20files/lect4-biogeochemistry.PDF