Water Systems The Water Cycle, Streams, and Ground Water
Water Cycle • movement of water between the atmosphere, the land, and the oceans.
Evaporation • Water changing from liquid phase to a gaseous phase(water vapor) without boiling. • Surface 2/3 Water • 500,000 km3 /year • Evapotranspiration – evaporation from plant leaves.
Condensation • change of state from a gas to a liquid • When water vapor rises in the atmosphere, it expands and cools. • As the vapor becomes cooler; some of it condenses back to liquid • High – Clouds • Low – Fog • Surface - Dew
Precipitation • Any form of water that falls to Earth’s surface (rain, snow, sleet, and hail) • Most precipitation falls on Earth’s oceans. • The rest falls on land and becomes runoff or infiltrates the soil to become groundwater.
Runoff • Rain that falls to the ground and is not absorbed • Moves along the surface of the land until it flows into a stream system • Causes erosion.
Factors Affecting Runoff • Rate of rain Runoff • Slope Runoff • Buildings Runoff • Plants Runoff
River Systems • watershed (AKA basin)the area of land that is drained by a river system • The ridges or elevated regions that separate watersheds are calleddivides. • tributariesstreams that flows into a lake or into a larger stream • A river system is made up of a main stream and tributaries.
MooseheadLake Watershed • Contains: • 31 lakes • 549 m2 of land • 400 miles of rivers and streams • empties out into the Atlantic Ocean
River Systems • Channel - Depression that a stream follows as it flows downhill • Banks - The edges of a stream channel that are above water level • Bed - The part of the stream channel that is below the water level • A stream channel gradually becomes wider and deeper as it erodes its banks and bed.
River Systems stream load - Sediment carried by a stream • Stream load takes three forms • suspended load • bed load • dissolved load
River Systems Stream gradientthe change in elevation over a given distance • Near the headwaters, or the beginning of a stream, the gradient generally is steep. • As the stream nears its mouth, its gradient often becomes flatter. • The characteristics of streams with different gradients are very different
River Systems • River systems change continuously because of erosion. • Depending on the slope of the land, streams have three stages of development. Young, Mature, and Old • These differing streams support different types of organisms
Young Streams • Flow swiftly through a steep valley. • Lots of whitewater and waterfalls because they have not yet eroded all the material in their way. • Young streams erode most on the bottom and less on the sides.
Qualities • Fast Moving • High oxygen • Cold • Little Nutrients
Stream Merging • Many young streams join together to form larger streams. • Depending on the slope of the land and the amount of water they will form either mature or old streams
Mature and Old Streams • Mature and Old Streams flow through floodplains. • floodplainan area along a river that forms from sediments deposited when the river overflows its banks • Occurs when water levels increase depending on the amount of rainfall and snowmelt in the watershed.
Mature Streams • Curving streams that flow down a gradual slope • Erode more on their sides than on the bottom. • This leads to the creation of meanders (curves in a stream)
Qualities • Lots of sediment/nutrients • Erosion from young streams • Slow moving • Algae can grow
Evolution of Mature Streams meander • When a river rounds a bend, the velocity of the water on the outside of the curve increases. • Increase erosion • On the inside of the curve, the velocity of the water decreases. • Increased deposition • Causes curves to widen
Oxbow Lakes • The curve enlarges while further erosion takes place on the opposite bank, where the water is moving more quickly. • Meanders can become so curved that they almost form a loop, separated by only a narrow neck of land • This can eventually become separated into an oxbow lake
Old Streams • Old streams flow very slowly through a broad flat floodplain. • Usually they have lost their meanders and flow more straightly.
Deltas and Alluvial Fans • Fan-shaped masses of sediment deposited as a stream slows • Deltas occur where streams meet oceans • Alluvial fans result where streams loose energy as the slope decreases rapidly.
Groundwater • Water that absorbs into the ground and is located in the spaces between sediments (pores) • These pores are connected and allow water to flow through them.
Permeability • Ability of a material(rock/sediment) to allow water to flow through it. • Permeable rock/sediment layers allow water to pass through easily • Impermeable rock/sediment layers resist the flow of water. • Depends on size and shape of sediment
Zone of Saturation • Ground water fills the pores in the permeable rock/sediment layer creating an aquifer. • The area of the soil where all of the pores have completely filled with water is referred to as the zone of saturation. • The upper limit of this zone is called the water table.