freshwater and society module 1, part b. developed by: munson, richards, svendsen updated: dec. 30,...

Freshwater and Society

Module 1, part B

Developed by: Munson, Richards, Svendsen Updated: Dec. 30, 2003

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Watersheds

http://www.epa.gov/owow/watershed/whatis.html


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Hydrological cycle of a watershed


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Watershed definition

Watershed: An area of land that drains water, sediment and

dissolved materials to a common receiving body or outlet

The term is not restricted to surface water runoff and includes interactions with subsurface water

Watersheds vary from the largest river basins to just acres or less in size


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Organization of watersheds:

A divide represents the boundary of a watershed Larger watersheds can often be divided into

smaller units called subbasins, drainage areas, or water resource inventory areas

http://www.epa.gov/watertrain/execmgmt/lyout2.htm


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Watersheds


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Watershed components

Latitude, albedo & climate

Geology Topography Land Use:

Vegetation and impervious surfaces

http://vathena.arc.nasa.gov/curric/weather/storm.html


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Watershed components: Latitude

Energy input into a watershed depends on solar height and length of daylight hours Determined by the

latitude and season May 21, Seattle, WA

solar altitude at noon is 62.500

January 21, Seattle solar altitude at noon is 22.500


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Watershed components: Albedo

Albedo is the reflectance of a surface. The higher the reflectance the less energy input into a watershed.

Surface Cover Albedo (%)

Water 5-10

Bare soil (light colored, dry) 20-35

Marsh and Bogs 15-20

Forest (dense spruce) 5-10

Forest (hardwoods in leaf) 15-20

Snow (fresh) 80-95

Snow (old) 40-70


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Temperature regime Relative humidity Precipitation patterns

Watershed components: Climate

http://www.eia.doe.gov/emeu/recs/origin/climzone.gif

http://www.epa.gov/ceisweb1/ceishome/atlas/nationalatlas/climatezones.htm


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Watershed components: Climate

Precipitation Temperature Relative humidity (RH) Wind

http://www.hanford.gov/docs/annualrp00/sumoverview.stm

http://www.habitat.fws.gov/images/river.jpg


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Watersheds: Average annual precipitation


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Watersheds: Potential evapotranspiration


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Watersheds: Water surplus or deficit


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Bedrock Type and distribution of soils

Watershed components: Geology

•http://www.soils.umn.edu/academics/classes/soil2125/doc/s2chap5.htm

http://geohazards.cr.usgs.gov/wa/lsphotos1/photos4.html


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The ease with which water penetrate or pass through a bulk mass of soil or a layer of soil

Geology: Soil permeability

http://www.nre.vic.gov.au/web/root/Domino/vro/vroimages.nsf/Images/gloss-ferr/

http://soils.usda.gov/gallery/state_soils/ http://soils.usda.gov/gallery/state_soils/


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Total porosity of a soil determines maximum water content at saturation; soils within zone of aeration are seldom saturated.

Textural (primary) porosity: voids between aggregates.

Structural (secondary) porosity: voids within aggregates – fracture or poor zones

Geology: soil pore space and water content

http://wrgis.wr.usgs.gov/open-file/of99-168/Pp-limestone.jpg


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Geology: Groundwater vs. soil moisture

Groundwater: Subsurface water in the zone of saturation that is

free to move under the influence of gravity, often horizontally to stream channels

Soil Moisture: Subsurface water in the unsaturated zone held

in place by capillary forces or osmotic pressure


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Geology: moisture content of various soils


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Infiltration is the flow of water downward through the upper layers of soil

Geology: Infiltration


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Geology: infiltration capacity during a storm


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Geology: soil moisture profile after a rain event

1) Before Storm2) End of Storm3) One day after4) Two days after5) Three days after

Adopted from: http://www.nre.vic.gov.au/web/root/Domino/vro/vroimages.nsf/Images/gloss-ferr/


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Geology: seasonal infiltration trends


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Geology: seasonal variation in watershed runoff


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Geology: Saturation and runoff generation


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Topography Slope Aspect

Watershed components: Topography

http://www.pes.poquoson.k12.va.us/images/marsh.jpg

http://www.cce.cornell.edu/onondaga/watersheds/images/fallcolor2.jpg

http://volcanoes.usgs.gov/Hazards/What/PF/PFUnzen.html


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Watershed components: Topographic interactions

http://www.nrmsc.usgs.gov/research/glacier_model.htm


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Watershed components: Land use and vegetation

Vegetation Slows runoff Reduces soil

compaction Prevents soil erosion Reduces pace of

raindrop splash Reduce soil material

moving downslope Influences timing of

snowmelt runoff Influences water yield

http://www.nature.nps.gov/pubs/I&M1998/Peer-01.htm

http://www.cce.cornell.edu/onondaga/watersheds/images/fallcolor2.jpg


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Land use: Stormwater discharge vs. land use


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Land uses: Effects upon hydrology/water quality

Natural Events Fires Wind storms Disease

outbreaks Floods Volcanoes Climate

change

Land Uses Flood control Timber

production Urban

development Hydroelectric Agriculture Mining

Waterquality

Watershedhydrology


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Watershed components: land Use


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Organization of a watershed


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Water budget Evaluation of sources of supply vs. discharges with

respect to a drainage basin

Watershed: Water budgets

Potlatch, IdahoSpearfish, South Dakota


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Annual water budget for Lawrence Lake, Michigan, and Mirror Lake, New Hampshire



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Water budgets provide a graphic depiction of the distribution of moisture throughout the year in any given area

An idealized budget, however, is rarely achieved

Examples from Los Angles, CA and Pullman, WA, illustrate the range of potential deviation from the “ideal” water budget

Fig. 8.4


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Watershed water budget: Pacific Northwest


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Watershed: Aquatic ecoregions

North America has been divided into eight major aquatic ecoregions: Arctic rivers and lakes Large temperate lakes Temperate headwaters and lakes Large temperate rivers Endorheic rivers, lakes, and springs Xeric-region rivers, lakes, and springs Temperate coastal rivers and lakes Subtropical coastal rivers and lakes


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Aquatic Ecoregions of North America


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Geomorphology Climate

Land uses

Vegetation

Watershed hydrology

Albedo

Watershed components

freshwater and society module 1, part b. developed by: munson, richards, svendsen updated: dec. 30,...

Documents

watershed componentslatitude

watershed definitionwatershed

water surplus

water contenttotal porosity

maximum water content

surface water runoff

soil moistureground

organization of watersheds