Water Resources & the Technologies We Use to Harness Them Water Technologies Thinking with Data: Science Part 2
Discussion Question Why is water necessary for life?
Discussion Question What percentage of all of the water on earth is fresh water?
Discussion Questions If most of the surface water is in lakes and rivers, how can we get the water to places where people live and grow crops? And, if most of the available water is stored underground, how can we get that water to the surface so we can use it?
What Dams Do • Store water during the rainy season • Control periodic floods
What Dams Do • Produce electrical energy http://earthsci.org/mineral/energy/hydro/hydroplant-animate.gif
What Dams Do • Provide recreation areas (fishing, boating) • Redirect river water to new locations for farming and domestic use
Discussion Questions What do you think are the most important uses of dams? Do you think that dams can cause any problems? If so, what might they be?
Problems Caused by Dams • Dams change the pattern of the rivers’ natural cycles. The new patterns may not provide the food and shelter needs of the plants and animals living there.
Discussion Question Dams stop flooding. What kind of problems might occur if floods are stopped?
Problems Caused by Dams • Floods take nutrients from the land to the rivers. • Animals who live in or by the water often coordinate their reproductive cycles with flood seasons so their young have food to live.
Problems Caused by Dams • Floods also deposit rich silt onto the flood plains, creating nutrient rich land for agriculture.
Silt Normal silt Silt is trapped and builds up behind the dam. The water released by the dam is without silt. • Silt consists of very small particles of dirt and rock. Normal river water carries silt. • When river water is trapped by a dam, the silt is deposited on the bottom and builds up behind the dam. • The water released by the dam has no silt.
Problems Caused by Dams • If the dam releases water once in a while, the high energy and coldness of the sudden floods picks up and removes silt, sand, small animals, and woody debris. A healthy living river needs the sediment and warmth to provide a habitat for animals.
Discussion Question Is it better or worse to have dams?
Before we look at the technologies designed to get our fresh water to the people and the places it needs to go, let us take a closer look at our major source of fresh water - groundwater
What is Groundwater? http://groundwater.sdsu.edu/groundwater_utilization_and_sustainability_01.jpg
What Wells Do • Tap groundwater for drinking and irrigation.
Problems With Wells • Wells may deplete a nonrenewable source of groundwater. • If the groundwater that the well is drawing from is contaminated, the water used for drinking or agricultural will also be contaminated.
Discussion Question What kinds of problems might interfere with us having all of the fresh, clean water that we need?
Water Availability Uneven distribution of water resources Changing (and growing) population Dams Different climates in different regions Water Sharing Who decides what is fair? Water Pollution Salinity Industrial pollution Urban stormwater sewage Shipping Mining Agricultural What Can Cause Problems With Our Current Water Supplies?