WATER Chapter 11, Section 1: Water Resources Standards: SEV5e
The Water Cycle • The same amount of water had been on the planet for billions of years. • The water you drink today is the same water dinosaurs drank! • Water is a renewable resource that is recycled through the water cycle.
The Water Cycle • Evaporation • Water evaporates when heated by sun (leaves salts behind) • Transpiration- water evaporation from plants • Condensation • As water vapor rises it cools, condenses, and collects on dust particles in the sky (condensation nuclei) and forms clouds. • Precipitation • When clouds get too full of water they drop it as precipitation • Infiltration and Runoff • Water either • Infiltrates the soil- pass slowly through soil to recharge an aquifer • Runs off into a nearby lake or stream.
How much water is on Earth? • 97% is saltwater in oceans & saltwater lakes. • 3% is freshwater • 2% frozen in ice caps & glaciers (unusable) • 1% groundwater & surface water (usable)
How is our usable water distributed? • Surface water • Groundwater
What is surface water? • Fresh water above ground. • Important for • Drinking water • Transportation of goods via ships • Irrigation • Aquaculture • Power for industry
What are the types of Surface Water? • Rivers & streams • Fast moving • Cold, highly oxygenated • Insect larvae, trout, long narrow plants, algae • Lakes & ponds • Slow moving • Warm, less oxygenated • Bass, catfish, cattails, leeches • Wetlands • Covered with water most of the year • Absorb and slow water flow • Filter pollutants & sediment • Provide breeding ground for water birds, shellfish, fish
What is a river system? • Streams form in higher elevations from rainfall or melting snow. • As they move downhill they combine with other streams to form rivers. • Streams that feed rivers are called tributaries. • This interconnection of streams to form rivers is the river system • Ex: McEachern creek flows to Noses Creek to Sweetwater Creek to Chattahoochee River
Chattahoochee River Lake Lanier West Point Lake Flint River Walter F. George Lake Apalachicola River Lake Seminole
What is a watershed? • Area of land that drains into a stream/river. • Pollution anywhere in the watershed could end up in that river. • We live in the Chattahoochee River watershed
What is groundwater • Fresh water stored underground in aquifers • Most fresh water resources are stored here • Aquifer- area underground with rocks & gravel that have spaces where water can accumulate.
What is the water table? • Top layer of water in aquifer where soil is saturated. • In wet regions the water table may reach surface and create a natural spring. • If aquifer is confined by layer of rock may be under pressure and squirt out of ground as artesian well • In desert regions water table is usually very deep.
Ogallala Aquifer • One of the largest in the world. • Supplies 1/3 of groundwater used in the U.S. • Used mostly for irrigating crops. • Now being used at increasing rate (faster than can be recharged) • Water table has dropped 100 ft in some places of Ogallala. • Wetlands rely on water table of Ogallala where it comes to surface. • If water table decreases, wetlands dry out, water birds (sandhill cranes) lose feeding & breeding site. • Farmers are trying to limit their use by switching to crops that require less water (wheat & sorghum)
What factors affect aquifer recharge rate? • Porosity • Percentage of total volume of a rock that has spaces • Water is stored in these pore spaces • More porous the rock, the more water it can hold. • Permeability • Ability of rock or soil to allow water to flow through it. • Sand- high permeability- lets water flow through quickly. • Clay- low permeability- holds water so it flows slowly. • Limestone, sandstone are permeable materials that often form aquifers.
How does an aquifer recharge? • When it rains, water percolates through region of soil called recharge zone. • Recharge zone is determined by what is on surface of soil above • Buildings, parking lots reduce recharge zone • Pollution can contaminate recharge zone & contaminate aquifer. • Can take 10’s of 1,000’s of years to recharge
How do wells impact groundwater sources? • Well- hole dug/drilled to reach groundwater • Well water is filtered by soil before it reaches aquifer- relatively clean. (usually filters are added on the pump that draws the water up) • Must reach way below the water table b/c water table changes seasonally. • If water is pumped out quickly it will create a cone of depression that may prevent other wells from reaching water.
You should be able to… • Describe the distribution of water on Earth. Where is most of the freshwater located? • Explain why fresh water is considered a limited resource. • Explain why pollution in a watershed poses a potential threat to the river system that flows through it. • Describe how water travels through rocks and soil.