Chapter 9: Surface Water BIG IDEA: Surface water moves materials produced by weathering and shapes the surface of the Earth

MAIN IDEA: RUNNING WATER IS AN AGENT OF EROSION, CARRYING SEDIMENTS IN STREAMS AND RIVERS AND DEPOSITING THEM DOWNSTREAM. Objectives: Describe how surface water can move weathered materials. Explain how a stream carries its load. Describe how a floodplain develops.

9.1 Surface Water Movement  Running water is the most important agent of erosion, set in motion by gravity and the water cycle.  The Water Cycle - all of earth’s water is continually moved and recycled through this process

9.1 Surface Water Movement 9.1 Surface Water Movement

9.1 Surface Water Movement  Evaporation- water turns into a gas and enters Earth’s Atmosphere  Transpiration – water in plants escapes through the leaves and turns into water vapor

9.1 Surface Water Movement  Condensation – when water vapor turns back into liquid water; makes clouds  Precipitation – any kind of water, liquid or solid, that falls from the sky

9.1 Surface Water Movement  Runoff- water flowing down slope along Earth’s surface –Factors affecting runoff: –soil composition –rate of precipitation –vegetation, –slope

9.1 Surface Water Movement  Streams: –Stream systems –Tributaries – rivers that flow into other streams –Watersheds – all of the land whose water flows into a specific stream –Divides – highland areas that separate watersheds

9.1 Surface Water Movement

Watershed (drainage basin)

U.S. River Drainage Basins

Watersheds in the U.S.

St. Lawrence Watershed

Colorado River Watershed

Columbia River Watershed

9.1 Surface Water Movement  Stream load- the materials that are suspended in and carried by the stream –generated by weathering and erosion –the carrying capacity is how much suspended material a stream can hold

9.1 Surface Water Movement  Drainage Basin - area of land surface drained by a river system.  Floodplain - wide, level area that borders a stream and is covered by its water in time of flood.

9.1 Surface Water Movement  Discharge - volume of water flowing past a certain point in a given unit of time. Q = W x D x V –the steeper the gradient the smaller the discharge –the smaller the gradient the larger the discharge

9.1 Surface Water Movement Q = W x D x V

9.1 Surface Water Movement Ex) A stream is record to have a width of 5 meters and a depth of 1 meter. The speed of the stream measured at the recording station was found to be 1.5 m/s. What is the streams discharge rate?

9.1 Surface Water Movement  Base Level - the deepest level that a stream can erode. –Sea level is the ultimate base level.  Floods – when water overflows the banks of the stream

9.2 Stream Development  MAIN IDEA: Streams erode paths through sediment and rock, forming v-shaped stream valleys.  Objectives: –Describe some of the physical features of stream development. –Describe the relationship between meanders and stream flow. –Explain the process of rejuvenation in the stream development.

9.2 Stream Development  Stream Development: Stream Development: Stream Development: –The stream channel is the path that is carved by the water flow –the banks are the land on either side of the stream –the driving force of the stream is the force of gravity on water.

9.2 Stream Development  Meanders – a bend or a curve in the stream caused by the moving water Meanders –water along the straight part of the stream:  the sides and the bottom move slowly because of friction  water along the meander : outside fast, inside of the bend is slow  an oxbow lake will form over time as a meander larger and becomes cut off

Meandering Stream (erosion & deposition)

Meandering Stream Oxbow Lake Cutoff Cut Bank Point Bar

What Feature is Carter Lake, Iowa?

River Phases (not in notes)

River Phases continued

Developing Floodplain

9.2 Stream Development

Floodplain

 Deposition of Sediments: –deltas form when a stream enters a large body of water  creates a triangle shape –alluvial fans form when the speed of the stream decreases and the load drops

Mississippi Delta 1979 → 1989

9.2 Stream Development

Distributaries – Ganges River

9.2 Stream Development

 The headward erosion of Stream A cuts into Stream B and draws away from its water into one stream, in a process called stream capture or piracy.

9.3 Lakes and Freshwater Wetlands  MAIN IDEA: As the amount of water changes and the amount of sediments increases, lakes can be transformed into wetlands and eventually into dry land.  Objectives: –Explain the formation of freshwater lakes and wetlands. –Describe the process of eutrophication. –Recognize the effects of human activity on lake development.

9.3 Lakes and Freshwater Wetlands  Lakes: a body of water surrounded completely by land –Some lakes form when stream flow becomes blocked by sediment from landslides. –Other lakes, such as moraine-dammed lakes, cirque lakes, and kettle lakes, have glacial origins.

9.3 Lakes and Freshwater Wetlands  A depression that receives more water than it loses to evaporation or use by humans will exist as a lake for a long period of time. However, over geologic time, most lakes are temporary features.

9.3 Lakes and Freshwater Wetlands

 The process by which bodies of water become rich in nutrients that stimulate excessive plant growth is called eutrophication. –Although eutrophication is a natural process, it can be sped up with the addition of nutrients, such as fertilizers, that contain nitrogen and phosphorus.

9.3 Lakes and Freshwater Wetlands

 Wetland: any land area that is covered with water for a part of the year.

9.3 Lakes and Freshwater Wetlands  Wetlands include environments commonly known as bogs, marshes, and swamps, which have certain soil types and support specific plant species. –Wetlands play a valuable role in improving water quality. –They serve as a filtering system that traps pollutants, sediments, and pathogenic bacteria contained in water sources.

9.3 Lakes and Freshwater Wetlands