Chapter 6 Running Water and Groundwater

Section 6.1 Running Water Water is found in oceans, rivers, glaciers, lakes, air, and soil. 97.2% is found in the oceans, 2.15% is found in ice sheets and glaciers, leaving only 0.65% to be divided among lakes, streams, groundwater, and the atmosphere. Water constantly moves among the oceans, the atmosphere, the geosphere, and the biosphere. This unending circulation of Earth’s water supply is the Water Cycle.

The Water Cycle

Water Cycle Processes Evaporation – water turns into gas (water vapor) and rises in the atmosphere. Transpiration – the release of water vapor by plants. Condensation – water vapor condenses into clouds. Precipitation – rain, snow, sleet, and hail falling back to Earth. Runoff – excess water from precipitation runs into river, lakes, etc. Infiltration – movement of surface water into rock or soil through cracks and pore spaces becoming groundwater.

Streamflow The ability of a stream to erode and transport materials depends largely on its velocity. Factors that determine velocity are gradient, the shape, size, and roughness of its channel, and its discharge. Gradient – the slope or steepness of a stream channel. Discharge – the volume of water flowing past a certain point in a given unit of time. Tributary – a stream that empties into another stream. Meanders – a wide curve in a river.

Meanders and Oxbow Lakes An oxbow lake is an abandoned meander that stays filled with water.

Section 6.2 The work of streams Streams are Earth’s most important agents of erosion. Streams generally erode their channels by lifting loose particles, by abrasion and grinding, and by dissolving soluble material. Streams transport sediment in 3 ways: 1. in solution (dissolved load) 2. in suspension (suspended load) 3. bouncing or rolling along the bottom (bed load)

Deposition Deposition of sediments occurs when streams and rivers slow down. This usually happens when it enters an ocean, sea, or lake. A delta is an accumulation of sediment formed when a stream enters a lake or ocean.

Stream Valleys River valleys are naturally V – shaped. Narrow valleys – usually associated with young streams. Includes a lot of rapids and waterfalls. Still downcutting toward base level. Wide valleys – the stream has cut its channel to base level. The stream now cuts from side to side creating a floodplain, or flat valley floor. Usually associated with older, more mature rivers. Natural levees are natural banks of sediment deposited on the sides of streams when they flood.

River Valleys

Floods and Flood Control Flood – when a river or stream overflows its banks. Usually caused by heavy rain or rapid snow melt. Measures to control flooding include: Artificial levees – walls or banks built by people alongside a river. Dams – store floodwater to be let out slowly. Limiting development on floodplains. Artificial floodways – emergency river channels around towns and cities that flood water runs through.

Drainage Basins Drainage Basin – the land area that contributes water to a stream. Also known as watershed. Divide – separates drainage basins of two streams.

Section 6.3 Groundwater Porosity – the amount of pore space, or holes, that a rock has. Permeability – the ability to transmit a fluid Permeable rock allows water to pass through it. Impermeable rock does not allow water to pass through it. Groundwater moves by twisting and turning through interconnected small openings, or pores. The groundwater moves more slowly when the pore spaces are smaller. Aquifers – large areas that are a source of well water.

Distribution of Groundwater Zone of saturation – area where groundwater fills all of the pore spaces in sediment and rock. Water table – the top or the zone of saturation. It changes based upon precipitation. Zone of aeration – area above the water table where the ground is not saturated or filled with water.

Groundwater Spring – forms whenever the water table intersects the surface. Geyser – an intermittent hot spring, where superheated water shoots upward with great force.

Groundwater Well – a hole bored into the zone of saturation. This results in a cone of depression in the water table around the well. Artesian well – groundwater rises on its own under pressure. A desert oasis is an example. Contamination and overuse threatens groundwater supplies in some areas.

Karst Topography Many areas of the world have landscapes shaped by the dissolving power of groundwater. These areas are said to have karst topography. This area is one of them. Karst areas contain a lot of limestone that is dissolved through the process of carbonation forming caverns and caves. Karst areas typically have irregular terrain, with many depressions called sinkholes. They also have a lot of caves, caverns, and disappearing springs. Stalactites hang from the ceiling of a cave or cavern. Stalagmites grow from the floor upward in a cave or cavern.

Pictures of Karst Topography

Pictures of Karst Topography

Pictures of Karst Topography