Chpater 17: The hydrologic Cycle and Ground Water

Fresh water statistics

4.34×10^7 km - glaciers and polar ice(fresh solid water, fresh liquid water - underground waters(1.54×10^7), lakes and rivers (1.27×10^5 km ³)

water facts

high heat capacity, and effective in climate regulation, 3 phasesenergy consumed by the cycle(melting and evaporation) and energy is released by precipitation

the hydrological cycle

most evaporations occur over the oceans, knowing flux and resercvoir size, a residence time(time in the reservoir) can be calculated, groundwater slowly moves through porous rocks; infiltrate: water soaks into the ground

climate distribution

tropical regions near the equator receive the most solar radiation, polar regions receive teh least solar radiation, arid regions exisit on all continetns at approximately 30 degrees north and south latitiudes

how do physical features effect precipitation

the division between wet and dry in participation is strongly influenced by lasndscape(sierra nevada very dry and rocky mountains pretty wet)

orographic rain shadow effect

winds carry warm air over oceans where it gathers moisture, the moit air rises and condences, precipatating rain or snow, then the result is a rainy windward slope, and the cool air sinks and warms, finally a rain shadow is formed. California interior is dry because of the rain shadow effect, air can hold less water when it cools resulting in orographic precipitation

storage of surface runoff water

surface runoff collects in wetlands and lakes along mississippi river which acts as buffer zones for water storage

dry period

streams bring in small amounts of water and carry away small amounts - low runoff

groundwater

an underground bed or layer of permeable and high porosity rock, sediment, or soil that yields water. some amount of precipitation eventually becomes ground water;

high porosity rounded sand grains hold more water, low porosity cemented sandstone holds less water, unfractured shale is vary impermeable to groundwater

watertable

defines teh boundary betweeen unsaturated zone and saturated zone

ground water flow

surface water infiltrates into the unsaturated zone by gravity and capillary froces and moves into the watertable, it moves from high pressure ot low pressure(typically high elevation to low elevation)

karst topography

limestone bedrock eroded by groundwater Mammoth Cave NP; Guilin in China);

Karst is also expressed at the surface with the formation of sinkholes, springs, caves, and swallow holes.

An example of karst terrain is the Texas Hill Country

groundwater contamination

Lead pollution: Lead from pipes may partially dissolve in the water flowing through. Lead may bind to carbonate, therefore lower amounts of lead dissolve in

hard water.

Radioactive wastes: Oak Ridge, Tennessee and Hanford have already leaked radioactive wastes into shallow water. Fukushima Daichii is another example.

Microorganisms: microbes live in water; leaking septic tanks can release microbes into groundwater.

Chemicals: such as chlorinated solvents, fertilizers, nitrate.

ground water extraction

salt water is denser than fresh ater, so near teh cost freshwater aquifiers lie on topof salteerwater;

too much pumping of water can cause ground sinking an dsaltyw ater discharge

ground water recharge

ground water recharge is after heacy rain, the water infiltrates into the unsaturated zone and rechanrges the ground water reservoir. the water table increases in wet seaeson but decreases on dry season

water table depression

extraction fo water exceeding natural water recharge will eventually lead to water table depression

groundwater withdrawls

When pumping exceeds recharge by infiltration, the water is being mined, and the resource will eventually be depleted.

The rate of groundwater use in the U.S. today greatly exceeds the rate of recharge