PG.81 Sources of water

Water on earth All water on earth constitutes the hydrosphere 97% is stored in oceans 2% in glaciers 1% lakes, streams, ground water and the atmosphere

Hydrologic Cycle Water is in a continuous cycle powered by energy from the sun 4 processes:  Evaporation  Condensation  Precipitation  transpiration

The cycle Water from the oceans evaporates  wind carries it until it condenses into clouds  precipitation occurs Water that falls onto continents must make its way back to the ocean Some water soaks into the ground (infiltration) Plants absorb water from the ground and release it back in the atmosphere (transpiration) When rate of rainfall exceeds earth’s ability to absorb it, runoff occurs

Factors that affect Runoff Water flowing down a slope is runoff Vegetation- more of it  less run off Rate of precipitation  heavy rains, more runoff Soil composition  more organic material, more porous; bigger particles, more porous = less runoff Slope  larger the slope  more runoff

Streams Land area whose water drains into a stream system is call a watershed Ability to erode depends on gradient, shape, size, and roughness of the channel Can measure discharge (volume that flows over a particular location in a certain amount of time) Discharge= volume of water flowing past a certain point in a given amount of time

Lakes Lakes can come from:  Meandering streams that cut off a portion  Glaciers that carve depressions  Dammed streams from landslides Eutrophication is the process by which lakes become rich in nutrients from the surrounding watershed

Wetlands Land that is covered with water for most of the year Includes bogs, marshes, and swamps Bogs:  Receive water from precipitation  Include peat moss that contributes to soil acidity Marshes:  Form along the mouth of streams with extensive deltas  Lots of grass and wildlife Swamps:  Low lying areas by streams  Marshes grow and become swamps

Groundwater Most freshwater is in glaciers rest in groundwater Zone of aeration- area above water table where soil is not saturated Zone of saturation- where groundwater completely fills all pores Upper boundary of zone of saturations  water table Ground water flows through permeable layers called aquifers

Erosion and deposition by groundwater Caves are formed when limestone dissolves Sink holes are formed when caves collapse or dissolution of bedrock Regions that have abundant sinkholes are said to have karst topography

Ground water deposits Water that has high concentrations of Ca, Mg, or Fe is called hard water Dripstone formations in caves are formed from water deposits Eventually form stalactites (hang from cave’s ceiling like icicles) Water drips off stalactites to form stalagmites

Ground water systems Springs- natural discharges of ground water  Hot springs-temps higher than the human body  Geysers- explosive hot springs Wells- holes dug or drilled to reach ground water  Artesian well- well that has enough pressure to spurt out water

Threats to our water system Overuse Subsidence- the sinking of land due to ground water depletion Pollution  Industrial waste  Landfills  Agricultural chemicals  Chemicals – salt and radon

Pg. 82 Create a diagram of the water table and include the following words or events:  The energy source  Precipitation  Condensation  Evaporation  Transpiration  Zone of saturation/zone of aeration  Ground water  Run off  Ocean  Stream  Lake  Water table  Aquifer