Water Resources Environmental Science Spring 2011

Objectives Describe the distribution of Earth’s water resources Explain why fresh water is one of Earth’s limited resources Describe the distribution of Earth’s surface water Describe the relationship between groundwater and surface water in a watershed

Water Cycle Freshwater: water that people can drink, contains little salt Salt water: contains higher concentrations of dissolved salts, people cannot drink, in oceans

Water Cycle Water is a renewable resource- circulated through water cycle Water evaporates at earth’s surface and leave behind salts and impurities Water vapor: gaseous water, rises in air Condensation: water vapor cools and turns into a liquid, falls to earth’s surface

Water Cycle

Global Water Distribution Freshwater is a limited resource 71% of Earth’s surface is water 97% Salt Water 3% Freshwater 77% Frozen in glaciers and polar icecaps

Surface Water Surface Water: freshwater on Earth’s land surface Lakes, rivers, streams, wetlands Provide drinking water, water to grow crops, food such as shellfish and fish, power for industry, and means of transportation

River Systems River systems: a flowing network of water formed as streams and rivers move across the land Amazon largest river system Streams form as water falling rain and melting snow drains from mountains, hills, plateaus, and plains Streams combine with other streams to form rivers

River Systems

Watersheds Watershed: area of land that is drained by a river Pollution anywhere in watershed may pollute a river Amount of water entering watershed varies throughout year

Ground Water and Water Table Groundwater: water beneath earth’s surface in sediment and rock formation Water percolates through soil and down into rocks underneath Water Table: level where rocks and soils are saturated with water At different levels, can range from at earth’s surface to 100’s of meters beneath the surface

Ground Water and Water Table

Aquifers Aquifer: underground formation that contains groundwater Water table forms upper boundary of aquifer Most consist of rocks, sand, and gravel that have a lot of space where water can accumulate

Porosity and Permeability Porosity: percentage of total volume of a rock that has spaces (pores) Water in aquifer is stored in pore spaces and flows between pores More porous, more water rock can hold Permeability: ability of rock or soil to allow water to flow through it Gravel is permeable; Clay, granite impermeable Most productive aquifers usually form in permeable materials (sandstone, limestone, layers of sand and gravel)

The Recharge Zone Recharge Zone: area of the Earth’s surface from which water percolates down into an aquifer Environmentally sensitive areas because pollution can enter aquifer Size of recharge zone is affected by permeability of surface above aquifer Surface water can take a very long time to refill an aquifer, buildings can prevent this

Wells Well: hole that is dug or drilled to reach groundwater Create wells because groundwater may be a more reliable source of water than surface water because water is filtered and purified as it travels underground

Review 1. Which of the following processes is not a part of the water cycle? A. Evaporation B. Condensation C. Biomagnification D. Precipitation 2. Most of the fresh water on Earth is: A. Located underground in aquifers B. Frozen in polar icecaps C. Located in rivers, lakes, streams, and wetlands D. Found in Earth’s atmosphere

Ansers 1. Which of the following processes is not a part of the water cycle? A. Evaporation B. Condensation C. Biomagnification D. Precipitation 2. Most of the fresh water on Earth is: A. Located underground in aquifers B. Frozen in polar icecaps C. Located in rivers, lakes, streams, and wetlands D. Found in Earth’s atmosphere