Earth Science Chapter 6: Running Water and Groundwater

Profile of a Stream

• A stream's profile is a smooth curve from its head to its mouth
• Gradient decreases from the head to the mouth
• Factors that increase downstream include velocity, discharge, and channel size
• Factors that decrease downstream include gradient, channel roughness, and slope

Tributaries and Base Level

• A tributary is a stream that empties into another stream
• Base level is the lowest point to which a stream can erode
• There are two types of base levels: ultimate (sea level) and temporary (local)

The Work of Streams

Erosion

• Streams erode their channels through abrasion, grinding, and dissolving soluble material

Deposition

• A stream's bedload is solid material too large to carry in suspension
• Capacity is the maximum load a stream can carry
• Deposition occurs when streamflow drops below the critical settling velocity of a certain particle size
• Deposits are called alluvium
• Deltas are accumulations of sediment formed where a stream enters a lake or ocean

The Water Cycle

• Water constantly moves among the oceans, atmosphere, solid Earth, and biosphere
• The water cycle involves evaporation, condensation, precipitation, infiltration, runoff, and transpiration

Streamflow

• Streamflow is the volume of water flowing past a certain point in a given unit of time
• Gradient is the slope or steepness of a stream channel
• Channel characteristics include shape, size, and roughness

Changes from Upstream to Downstream

• Gradient decreases from the head to the mouth, while discharge increases downstream

Groundwater

Distribution and Movement

• Porosity is the percentage of pore spaces in a rock
• Permeability is the ability to transmit water through connected pore spaces
• Aquifers are permeable rock layers or sediments that transmit groundwater freely

Features Associated with Subsurface Water

Springs

• A spring forms when the water table intersects the ground surface
• Hot springs have water 6-9°C warmer than the mean air temperature of the locality
• Geysers are intermittent hot springs where water turns to steam and erupts

Wells

• A well is a hole bored into the zone of saturation
• Artesian wells are formations where groundwater rises under pressure
• Pumping can cause a drawdown of the water table and form a cone of depression

Environmental Problems

• Overuse and contamination threaten groundwater supplies
• Land subsidence can occur due to withdrawal of groundwater

Caverns

• Caverns are naturally formed underground chambers
• Caverns can be formed by dissolution of groundwater

Stream Valleys

• Narrow valleys have a V-shape and show downcutting towards base level
• Wide valleys are flat and show lateral erosion
• Features of wide valleys include meanders, cutoffs, and oxbow lakes

Floods and Flood Control

• Floods occur when the discharge of a stream exceeds its channel capacity
• Measures to control flooding include artificial levees, flood control dams, and limits on floodplain development

Drainage Basins

• A drainage basin is the land area that contributes water to a stream
• A divide is an imaginary line separating the drainage basins of one stream from another

Types of Glaciers

• Ice sheet: a large, continuous ice mass covering a vast area
• Ice cap: a smaller, dome-shaped ice mass
• Ice shelf: a thick, floating plate of ice extending from a glacier onto the sea
• Iceberg: a floating piece of ice broken off from a glacier or ice shelf

Glacial Features

• Drumlins: elongated, teardrop-shaped hills formed by glacial deposition
• Eskers: long, narrow ridges of sediment deposited by glacial meltwater
• Outwash plains: flat or gently sloping areas of sediment deposited by glacial meltwater
• Kettles: depressions formed when blocks of ice break off from a glacier and melt
• Cirque: a semicircular valley formed by glacial erosion
• Arete: a narrow ridge of rock formed by glacial erosion
• Horn: a steep, pyramidal peak formed by glacial erosion