Unit 5 Chapter 15 River Systems

Section 1 The Water Cycle Remember from the beginning of the year we talked about the water cycle. Again, we are talking about it. It is a never ending process that repeats itself over and over again, from precipitation, to evaporation and back to precip.

Where is our water kept 97% of water is in oceans - salt water 2 ½ % of water is frozen - glaciers ½ % of water is fresh drinking Streams (very little) Rivers – very little Lakes – a little more Swamps – a little more What this really means is that 75% of the fresh water is in the form of Glaciers. 50% of the fresh water that we use for drinking and things is found UNDERGROUND, hence the word GROUND WATER

Terms to Know Evaporation - water vapor going into the atmosphere - usually by the sun, directly or indirectly - moisture source for local water budget. Transpiration - process by which green plants lose water through their leaves Evapotranspiration - evaporation & transpiration combined - the way most water enters the air Condensation - water gas (H2Og) changing to Water Liquid (H2Ol) There must be a condensation nuclei (dust) to form clouds Precipitation - gravity pulling water from the clouds,

Water Budget Water Budget – It is the balance sheet for rain (precipitation) and water usage. Terms: Surplus - more water than you need - storage is full Usage - less water than you need – using water from storage Deficit - precipitation less than needed, storage is becoming empty Recharge - rain greater than needed, adding water back into storage

Factors that affect our Water Budget Land use: 1. Deforestation- removing the trees there is nothing to hold water in ground or prevent run off on surface. 2. Slope of the land – if it is too steep, water will run off unless it is covered by vegetation or plants. 3. Urbanization – over use due to increase in population 4. Plant life – when covering the soil, can hold water, removed, allows water to run off. 5. Saltwater encroachment (infusion)- due to over pumping in areas by salt water, it will creep into the fresh water supply. 6. Permafrost – areas where the ground stays frozen up to 100 meters deep.

Water Use Over use is a very big problem. When all of the water is removed from underground the ground may become compacted and the ground level drops. This is called subsidence. Foundation failure and structure damage may result. Pollution: Chemicals – brought into the water table by pesticides, fertilizers, and other household items. Sewage – from urbanization Industrial wastes – toxic wastes, Radon – a natural radioactive gas that comes from the decay of uranium. Ground water areas close to this will become contaminated. Conservation of Water Laws have been put into place so that we can keep our water clean and abundant enough to use. There are also ways that we are trying to add to our fresh water supply. Desalination is one such process. Scientists are trying to remove the salt from ocean water and turning it into fresh water. It is too expensive at this time to do as a real solution.

Section 2 Stream Erosion Tributaries – A stream that runs into another stream Drainage Basin or Watershed – It is all of the land that drains into a river including all of the waters from the tributaries. Canyon (gorge, chasm) A river cuts directly down in resistant rock - vertical sides

Highlands/Divides The highland that separates one drainage basin from another is called a divide. The Great Continental Divide - The Rocky Mountains East – All waters enter the Atlantic Ocean or Gulf of Mexico West – All waters that reaches the Pacific Ocean

Mississippi River System This drains all land from the Rocky Mountains to Appalachian Mountains, north to Wisconsin

Channel Erosion Head ward erosion When water wears away of land at the head of a gully, stream or rivers. V-shaped Valleys Are formed by young streams and rivers; they flow fast. Erosion is quick - widens whole valley Gully -small v shaped valley formed by rain

Stream Piracy This occurs when head ward erosion eats through a divide and captures another river.

Stream Load How Streams Transport Materials 25% solution -material dissolved into water Ex. Ca, Mg, Fe, Na, CO2, O2 50% suspension-carrying rock materials Ex. clay, silt, fine sand 25% bed load -moving material along the bottom Ex. sand, pebbles, cobbles, boulders Carrying load – this is total amount of sediment a stream can carry and the size of the particles and on the velocity and volume of water

Stream Discharge Stream discharge is the volume of water flowing past a point in a certain period of time. Faster moving water carries more sediment. Velocity is the distance that water travels in a given amount of time Stream Gradient Gradient is the steepness of the slope of the stream. The gradient will change during the length of the river or stream. It will be great when going down a steep hill or small when approaching sea level. Base Level is the lowest level a stream or river gets to. It depends on where stream is flowing and the height above sea level or over what types of rocks. Sea Level is the ultimate base level because all rivers eventually empty there. Rapids – when a stream runs through a steep mountain range.

Water Falls This occurs when water falls over a cliff. Undermining – water falling from the falls wears away at the bottom of the cliff leaving an overhang. The overhang eventually falls and the waterfall moves upstream (recedes).

Niagara Falls

Development of River Channels When a stream load, discharge and gradient decreases, they become broader and slower moving, they now are called a river. Meandering Channels Rivers always shift to the outside of a bend - because the outside has the fastest moving water - most erosion. Meanders - broad curves of a river

Oxbow Lake is a cut off meander of a river Rivers decrease in speed and deposit sediment All sediment is deposited when a river enters a lake or ocean Braided Streams This occurs when multiple channels are divided and then again rejoined.

Section 3 Stream Deposition As a river turns a corner, it will decrease in speed and will deposit its sediment. Swifter moving water will carry the sediment much further.

Deltas and Alluvial Fans Delta -fan shaped deposits at the mouth of rivers -Sediments drop as water slows -The river channels are choked by its own sediment Alluvial Fan -land locked delta - formed as rain water flows down a steep cliff on to flat land

Floodplains Flood plains are areas where rivers can over flow. Levees A levee is elevated land along rivers they can be either natural or man made Back swamp is the low area behind levee, moist full of river deposits. Finer Flood Sediments Finer sediments are carried into the flood plains. It is associated with the swampy area that is along the rivers where the sediments are deposited.

Human Impacts on Flooding We contribute to flooding by the use of the land. Removing vegetation and trees allows for more free flowing water which creates flooding. Flood Control Prevention 1.Replant vegetation that was removed in flood areas 2.Use Dams like the Tennessee River System approx. 50 dams built to help control flooding 3.Use of artificial levees. (Use sandbags) 4.Create spillways, channels running along the river to trap water and move it away from where it would cause damage.

The Life Cycle of Lakes