Water Resources

Environmental Science Spring 2011

ObjectivesDescribe the distribution of Earth’s water

resources Explain why fresh water is one of Earth’s

limited resourcesDescribe the distribution of Earth’s surface

waterDescribe the relationship between

groundwater and surface water in a watershed

Water CycleFreshwater: water that people can drink,

contains little saltSalt water: contains higher concentrations

of dissolved salts, people cannot drink, in oceans

Water CycleWater is a renewable resource- circulated

through water cycleWater evaporates at earth’s surface and

leave behind salts and impuritiesWater vapor: gaseous water, rises in air Condensation: water vapor cools and turns

into a liquid, falls to earth’s surface

Water Cycle

Global Water DistributionFreshwater is a

limited resource

Surface WaterSurface 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 SystemsRiver systems: a flowing network of water

formed as streams and rivers move across the landAmazon 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

WatershedsWatershed:

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 TableGroundwater: 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

AquifersAquifer: 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 PermeabilityPorosity: 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 ZoneRecharge 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

WellsWell: hole that is dug or drilled to reach

groundwaterCreate wells because groundwater may be a

more reliable source of water than surface water because water is filtered and purified as it travels underground

Review1. 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 aquifersB. Frozen in polar icecaps C. Located in rivers, lakes, streams, and wetlandsD. Found in Earth’s atmosphere

Ansers1. 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 aquifersB. Frozen in polar icecaps C. Located in rivers, lakes, streams, and wetlandsD. Found in Earth’s atmosphere