Surface Water Chapter 6

Water Cycle

6.1 Streams and Rivers River Systems (structure) Tributary- a stream that runs into another stream or river River system- a river and all of its tributaries Drainage basin, or watershed- all the land that drains into the river either directly or through its tributaries Mississippi River system Divide- high land that separates one drainage basin from another Continental Divide in the Rocky Mtns

Headwaters/Source- beginning of stream or river Mouth- end of the stream or river where it enters into another body of water

Characteristics Velocity- distance that water travels in a given amount of time Related to the amount of energy that the water has Erosion occurs more quickly Other characteristics affect the velocity Gradient- steepness of the slope of a stream or river Steep at its source; gradual at sea level

Characteristics cont… Discharge- the amount, or volume, of water that passes a certain point in a given amount of time Not constant over length of a river Increases downstream as tributaries add more water Not constant year-round- increased precipitation/melting snow Channel- the path through which the water flows in a stream or river Shallow, winding stream with many boulders has contact with surface area that causes it to slow down by friction Straight channel that is wide and deep has less surface area in contact with water, so velocity is greater

6.2 Stream Erosion and Deposition Deposition- the process by which materials are deposited Occurs because the river or stream no longer has enough energy to transport them Erosion by rivers Running water wears down Earth’s surface by breaking up bedrock and by removing eroded rock and soil materials Breaks up materials by mechanical means Abrasion mainly; in time, creates rounded boulders, pebbles, and sand grains from the cutting tools

Transported Material (Load) Dissolved Substances- smallest particles are dissolved Suspension- a state in which rock materials carried by a river are stirred up and kept from sinking by the turbulence of stream flow Bedload- sand, pebbles, and boulders that are moved along the bed of a stream and that are too heavy to be carried in suspension

Transporting Materials Two measures are used to describe the ability of a stream to transport materials Competence- a measure that describes the maximum size of the particles a stream can carry Capacity- a measure of the total amount of sediment a stream can carry Depend on the velocity and discharge Vary along a stream and change throughout the year High velocity + High discharge = large amount of sediment and larger sizes of sediment particles

Depositional Features Delta- a fan-shaped deposit that forms when a river flows into a quiet or large body of water River water comes to almost a standstill at a delta Distributaries- branches formed by rivers flowing over its delta Responsible for delta’s shape Formation is delicate balance between deposition and erosion

Stream Valleys Narrow valleys Wide valleys narrow V-shaped valley shows that the stream’s primary work has been downcutting toward base level Features: Rapids and waterfalls Wide valleys Downward erosion is less dominant More energy is directed side to side Floodplain- the flat, low-lying portion of a stream valley subject to periodic flooding

Floodplains Streams that flow on floodplains move in meanders Cutoffs- shorter channel segments Oxbow lakes- abandoned bend of a river/stream

Floods Most caused by rapid spring snow melt or storms that bring heavy rains over a large region Ex: Mississippi River in 1993 Measures to control flooding Artificial Levees- earthen mounds built on the banks of the river Flood-control dam- store floodwater and then let it out slowly Limits on floodplain development- minimizing the development on floodplains

6.3 Water Beneath the Surface Much of the water in soil seeps downward until it reaches the zone of saturation The area where water fills all of the open spaces in sediment and rock Groundwater is the water within this zone Water table- upper limit of zone of saturation Zone of aeration- area above water table where the soil, sediment, and rock are not saturated

Groundwater

Movement Porosity- the percentage of the total volume of rock or sediment that consists of pore spaces Permeability- the ability to release a fluid Aquitards- impermeable layers that get in the way or prevent water movement Aquifers- permeable rock layers or sediments that transmit groundwater freely

Springs A flow of groundwater that emerges naturally at the ground surface Forms whenever the water table intersects the ground surface Hot springs 6°C - 9°C warmer than average annual temperature Source of heat is cooling igneous rock Geysers Intermittent hot spring or fountain in which a column of water shoots up with great force at various intervals

Below: Old Faithful Geyser Eruption Above: Geyser formation

Wells Hole bored into the zone of saturation Irrigation for agriculture Industrial use Home use Cone of depression- feature formed when too much water is being drawn out in a short period of time Artesian well- any formation in which groundwater rises on its own under pressure water must be in an aquifer that is tilted so that one end is exposed at the surface Must be aquitards both above and below the aquifer to stop the water from escaping

Artesian Well

Karst Topography Karst topography- landscapes that have been shaped largely by the dissolving power of groundwater Typically have irregular terrain, with many depressions Sinkholes- depression produced in a region where groundwater has removed soluble rock Form in one of two ways Gradually develop; fairly shallow and have gentle slopes Form when roof of cavern collapses; steep-sided and deep

Sinkholes South Florida Karst Virtual Field Trip FLORIDA ATLANTIC UNIVERSITY Department of Geosciences South Florida Karst Virtual Field Trip Introduction Miami Oolite Karst Definitions Karst Links S. Florida Karst Sites Acknowledgements Sinkholes Source:  http://ga.water.usgs.gov/edu/pictures/sinkhole2.jpg Source:  http://www.polkonline.com/images/081900/sinkhole.jpg

Environmental Problems Overuse and contamination threatens groundwater supplies in some areas Nonrenewable resources Subsidence- ground level sinks Contamination Septic tanks, farm wastes, inadequate or broken sewers Fertilizers, pesticides, highway salts Cleanup Abandoning water supply Pumping and treatment

SALT WATER INTRUSION What’s going on here? Ever noticed this at the beach? Man… that shower was salty!! (and the tap water, too!!!) So… what is this caused by again? Aquifer depletion! And what else is caused by this??? Sinkholes!

Contamination