Running Water Sect 6-1

A. Where is the Water? Largest portion of all water? Most freshwater? Second most freshwater? PBS Two Texas Towns run out of water (10 min) june12/texaswater_03-20.html

A. Where is the Water?

B. Water Cycle Powered by Sun and Gravity How? Evaporation Condensation Precipitation Infiltration Percolation Runoff Transpiration

Stomata (opening) on a leaf. B. Water Cycle Transpiration

B. Water Cycle Water cycle is balanced Avg annual precip = evaporation (globally)

C. Streamflow Gravity influences how water gets to oceans (downhill) Where is velocity highest in a river? – Middle – Outside edge of bends

C. Streamflow Ability to erode and carry sediment depends largely on velocity Velocity depends on: 1. Gradient (slope): steep = more energy

C. Streamflow Velocity depends on: 2. Channel Characteristics (shape, size, roughness) -all relate to friction with bottom of stream More friction: smaller, irregular stream channels

C. Streamflow Velocity depends on: 3. Discharge (volume of water) - more water means higher velocity (b/c less friction within channel) - Factors: weather, season, urban development

D. Upstream to Downstream While gradient decreases between headwaters and mouth, discharge increases. B/c of tributaries Added water often make river faster downstream even though not steep.

E. Base Level The lowest point to which a stream can erode its channel. Ultimately sea level, but temporary base level could be a lake. As rivers near their base level they form meanders.

Green River, WY

Meander in Canyonlands N.P., Utah