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Fresh Water. Rivers. What Is Erosion? Erosion is the process by which soil and sediment are transported from one location to another. Water and Erosion Water is a major agent of erosion. Rivers often carry eroded materials long distances. Water Cycle. Water Cycle.
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Rivers • What Is Erosion? Erosion is the process by which soil and sediment are transported from one location to another. • Water and Erosion Water is a major agent of erosion. Rivers often carry eroded materials long distances.
Water Cycle • What powers the water cycle? • What is different about the water cycle in rural and urban areas? • Don’t forget sublimation, transpiration, and deposition!
River Systems • Tributaries A stream that flows into a lake or into a larger stream is called a tributary. • Watersheds A watershed, or drainage basin, is the area of land that is drained by a water system
Water Sheds • What water shed do you live in? • What water shed do I live in? • Are there other water sheds in N.C.?
Erosion • GradientGradient is the measure of the change in elevation over a certain distance. • Discharge The amount of water that a stream or river carries in a given amount of time is called discharge. • Load The materials carried by a stream are called the stream’s load.
River Stages • Youthful Rivers A youthful river erodes its channel deeper rather than wider. • Mature Rivers A mature river erodes its channel wider rather than deeper.
River Stages • Old Rivers An old river has a low gradient and little erosive energy. • Rejuvenated Rivers Rejuvenated rivers are found where the land is raised by tectonic activity.
Rivers and Farms • Even though flooding along rivers is potentially harmful, many farms are located near rivers. Why do people build farms along rivers?
Deposits • Placer Deposits Heavy minerals are sometimes deposited at places in a river where the current slows down. This kind of sediment is called a placer deposit. • Delta As its current slows, a river often deposits its load in a fan-shaped pattern called a delta.
Deposits • Floodplains The area along a river that forms from sediment deposited when a river overflows its banks is called a floodplain. • Flooding Dangers Floods can damage property and cause a loss of lives. Dams and levees are often used to prevent flooding.
Water • A family lives 50 km from the nearest stream or lake and gets water from a well. Where does the water in the well come from?
Water Table • The Water Table The zone of aeration and the zone of saturation meet at a boundary known as the water table.
Aquifer • Porosity The percentage of open space between individual rocks is called porosity. • Permeability A rock’s ability to let water pass through is called permeability.
Spring vs. Well • Artesian Springs An artesian spring is a spring whose water flows from a crack in the cap rock of an aquifer. • Wells A human-made hole that is deeper than the level of the water table is called a well.
Underground Erosion/Deposition • Cave Formations Although caves are formed by erosion, they also so signs of deposition, such as stalagmites. • Sinkholes The roof of a cave can collapse, which leaves a circular depression called a sinkhole.
Water Beneath the Surface Caverns Characteristics of features found within caverns • Formed in the zone of aeration • Composed of dripstone • Formed from calcite deposited as dripping water evaporates • Common features include stalactites (hanging from the ceiling) and stalagmites (growing upward from the floor).
Water Beneath the Surface Karst Topography Formed by dissolving rock at, or near, Earth's surface Common features • Sinkholes—surface depressions - Sinkholes form when bedrock dissolves and caverns collapse. • Caves and caverns Area lacks good surface drainage.
While hiking, you realize your canteen is almost empty. Why should you not fill the canteen with water from a nearby stream?
Pollution • Point-Source and Nonpoint-Source PollutionPollution that comes from one specific site is called point-source pollution. Nonpoint-source pollution is pollution that comes from many sources.
Water Beneath the Surface Environmental Problems Associated with Groundwater Overuse and contamination threatens groundwater supplies in some areas. • Treating it as a nonrenewable resource • Land subsidence caused by its withdrawal • Contamination
Contaminated Ground Water • What are some problems associated with contaminated ground water? • Why is ground water so hard to clean once it is contaminated?
What are some examples of point- source pollution? • What are some examples of nonpoint-source pollution? • Which one is easier to do something about? • Which one causes more problems?
What is in the water? • Dissolved Oxygen Fish and other organisms that live in water need dissolved oxygen in the water to live. • Nitrates Elevated nitrate levels in water can be harmful to organisms because they lower the amount of dissolved oxygen in the water. • AlkalinityAlkalinity refers to water’s ability to neutralize acid. Acid rain can lower water’s alkalinity.
How to clean water. • Primary Treatment In primary treatment, dirty water is passed through a large screen to catch solid objects. • Secondary Treatment In secondary treatment, the water is sent to an aeration tank, where it is mixed with oxygen and bacteria. • Another Way to Clean Wastewater A septic tank is a large underground tank that cleans wastewater from a household.
Water • Water in Industry About 19% of water used in the world is used for industrial purposes. • Water in Agriculture Water must be used in agriculture to facilitate plant growth. • Conserving Water at Home Many people save water by installing low-flow shower heads and low-flush toilets.