hydrologic cycle and water budget

one way we could have gotten water on earth

comet crash, brought ice which vaporized and atmosphere held onto it, hydrogen and oxygen and rich plant debris

another way we could have gotten water on earth

volcanos, OUTGASING, water and water vapor from below surface is released

how water is distirbuted

97.22% ocean, 2.78% fresh water, of that freshwater 77.78% is on the surface, out of the surface freshwater 99.357% is from ice and glaciers

the blank has operates for billions of years from the lower atmosphere to several kilometers beneath earth's surface

hydrologic cycle

water budget

surpluses and deficits

transpiration

plants releasing water through their leaves (plant sweat)

evapotranspiration

a collective term (evaporation + transpiration) for all the processes by which water in the liquid or solid phase at or near the land surface becomes water vapor

potential evapotranspiration (POTET)

the amount of water that would evaporate and transpire under unlimited soil moisture conditions

actual evapotranspiration (ACTET)

soil water limited evapotranspiration; the ACTET could be at the POTET rate (if no water limit) or a rate less than the POTET (limited by soil moisture)

wilting point

the minimal point of soil moisture the plant requires not to wilt

field capacity

the amount of soil moisture or water content held in the soil after excess water has drained away and the rate of downward movement has decreased (can't take anymore)

if soil moisture is LESS than the wilting point, ACTET \= ??

ACTET \= 0

if soil moisture is GREATER than the field capacity, ACTET \= ??

ACTET \= POTET

if soil moisture is between the wilting point and the field capacity, ACTET ??

ACTET varies between 0 and POTET (sweet spot)

moisture supply (precip) \=

actual moisture demand ACTET (moisture demand POTET - moisture shortage deficit) + moisture oversupply (surplus) +/- moisture savings (utilization or recharge)

precip \> POTET

surplus

precip < POTET

deficit

most surface water stored in

glaciers, permafrost, and polar ice

what are groundwater resources mostly used for

irrigation and drinking water

what is an aquifer

a rock layer that is permeable to groundwater flow adequate for wells and springs

what is an unconfined aquifer

an aquifer that has a permeable layer on top and an impermeable one beneath

what is a water table

it is the upper limit of the saturation zone

what is a confined aquifer

one bound above and below by impermeable layers

what is aquiclude

an impermeable body of rock

what is an artesian aquifer

confined aquifer containing groundwater that will flow upward through a wall without the need for pumping

groundwater movement and emerging at the surface

groundwater moves from areas of higher pressure and elevation toward areas of lower pressure and elevation

3 problems with overuse of groundwater

over-pumping, collapsing aquifers, saltwater intrusion

what part of the US is under water stress

Las Vegas