Lecture 18 Flashcards
Hydrologic cycle
Water moving through the environment.
Amount of water on Earth is relatively constant.
Interception
Falling rain or snow can either fall directly to surface OR be intercepted/caught on plants before getting to surface, then can evaporate or drop to ground.
Infiltration
Water seeps below surface.
Runoff
Flows downhill over surface.
Evaporation
Depends on relative humidity, wind, and temperature.
Relative humidity
Dry air will have more evaporation (more room to soak up water), wetter air will will have less evaporation.
Transpiration
Soil water taken up by plants and evaporated from surface of leaves.
Porosity
Amount of open space between soil particles.
What infiltration depends on.
Permeability
Ease with which water moves through soil.
Infiltration factors
Vegetation; plants slow runoff, giving more time to infiltrate and roots loosen soil, increasing permeability and porosity.
Animals; can increase infiltration by loosening soil or lower it by compaction of the surface.
Soil moisture
Water in soil; some attached to soil particles.
Capillary water
Temporarily attached, available for plants to use.
Attraction decreases as more water attaches.
Gravity water
Not attached water, gravity pulls it down.
Field capacity
How much capillary water can a soil hold?
Wilting point
Most capillary water gone, plants can’t get enough to stay healthy.
Groundwater
Where all pore spaces filled with water - no air (zone of saturation).
Important natural resources.
Renewable resource
Groundwater used and replaced by rainfall in humid environments.
Non-renewable resource
Groundwater that may not get replaced in arid environments.
Aquifer
Subsurface material that holds groundwater (porosity and permeability sufficient for water to accumulate).
Aquiclude
Subsurface material with low permeability. Prevents groundwater from moving through it.
Water table
Upper limit of groundwater.
Artesian well
Water table higher than top of well, so water flows freely.
Depends on subsurface rock layers.
Cone of depression
Using underground water often lowers the water table around the well, creating a cone/V shaped divot around the well.
Subsidence
In some places, groundwater helps hold up the surface. Remove groundwater and surface will sink.
Salt water intrusion
Along some coasts, removes fresh groundwater and salty water takes its place.
Overland flow
Sheet flow; flows in uniform sheet over surface.
Rill; small concentrated flow.
Gully; moderate concentrated flow.
Stream; larger flow. Generic term for any concentrated flow.
Throughflow
Water infiltrates soil but some moves parallel to slope and emerges downslope to become overland flow.
Baseflow
Some groundwater, under the right circumstance, may feed water into a stream.
Only works if water table is higher than the bottom of stream.
Relatively constant. Keeps water flowing between rainstorms.
Effluent stream
Water table higher than bed; stream is “perennial” if it is effluent/flows all year.
Influent stream
Water table below bed; stream is “ephemeral” if influent all year/flows only with overland flow.
Intermittent streams
Flows part of the year bc it is seasonally effluent.
Hydrograph
Graph of streamflow overtime.
