chapter 9Review
In this chapter, we have learned that fresh water is a critical, scarce resource. The major sources of fresh water are groundwater, surface water, and atmospheric water. When groundwater is extracted faster than it is replaced, we can experience dry water wells and saltwater intrusion. Humans alter the availability of water by constructing levees, dikes, and dams to constrain water movement. We transport water from one place to another using aqueducts and we are able to convert salt water into fresh water through distillation or reverse osmosis. The use of water among countries can be determined by calculating the water footprint of a country; developed countries typically have a larger water footprint than developing countries. Most water is used for agriculture, followed by industrial and household use. Recent changes in each of these sectors have improved water use and reuse efficiency and conservation.
Aquifer Unconfined aquifer Confined aquifer Water table Groundwater recharge Spring Artesian well Cone of depression Saltwater intrusion Floodplain Impermeable surface Levee Dike Dam Reservoir Fish ladder Aqueduct Desalination Desalinization Distillation Reverse osmosis Water footprint Hydroponic agriculture Gray water Contaminated water | A stair-like structure that allows migrating fish to get around a dam. The uppermost level at which the water in a given area fully saturates rock or soil. Wastewater from toilets, kitchen sinks, and dishwashers. A barrier that runs across a river or stream to control the flow of water. An infiltration of salt water in an area where groundwater pressure has been reduced from extensive drilling of wells. An area lacking groundwater due to rapid withdrawal by a well. The process of removing the salt from salt water. Also known as Desalination. The cultivation of plants in greenhouse conditions by immersing roots in a nutrient-rich solution. An aquifer surrounded by a layer of impermeable rock or clay that impedes water flow. A process by which water percolates through the soil and works its way into an aquifer. A process of desalination in which water is boiled and the resulting steam is captured and condensed to yield pure water. The water body created by a damming a river or stream. A structure built to prevent ocean waters from flooding adjacent land. The total daily per capita use of fresh water. A canal or ditch used to carry water from one location to another. A process of desalination in which water is forced through a thin semipermeable membrane at high pressure. Wastewater from baths, showers, bathrooms, and washing machines. The land adjacent to a river. The process of removing the salt from salt water. Also known as Desalinization. An aquifer made of porous rock covered by soil out of which water can easily flow. A natural source of water formed when water from an aquifer percolates up to the ground surface. A permeable layer of rock and sediment that contains groundwater. Pavement or buildings that do not allow water penetration. An enlarged bank built up on each side of a river. A well created by drilling a hole into a confined aquifer. |
Module 26 The Availability of water
Describe the major sources of groundwater.
Groundwater can exist as either confined or unconfined aquifers. Unconfined aquifers can be rapidly recharged, but they are susceptible to contamination from chemicals released by human activities. Confined aquifers are typically recharged slowly and are less likely to be contaminated by anthropogenic chemicals. Large withdrawals of water from an aquifer can cause cones of depression that result in wells going dry. In coastal areas, large withdrawals for fresh water can cause saltwater intrusion.
Identify some of the largest sources of fresh surface water.
Sources of fresh surface water include streams, rivers, wetlands, and lakes. Streams and rivers have traditionally overflowed their banks and deposited nutrient-
Explain the effects of unusually high and low amounts of precipitation.
The abundance of precipitation varies with climate around the world and this affects the availability of water for ecosystems and humans. Periods of drought can interact with human activities to alter the cycling of nutrients, cause the topsoil to be blown away, and cause the soil surface to become impermeable to future precipitation.
Module 27 Human Alteration of Water Availability
Compare and contrast the roles of levees and dikes.
Levees and dikes both use barriers to prevent flood water, but levees are built along rivers to prevent rising rivers from spilling over onto the floodplain whereas dikes are built near the ocean to prevent ocean waters from flooding the adjacent land.
Explain the benefits and costs of building dams.
Dams can provide multiple benefits including electric generation, flood control, and recreation. However, dams require a large amount of resources to construct, they often displace people, and they have ecological effects including interference with fish migration and prevention of seasonal flooding that some species require to persist.
Explain the benefits and costs of building aqueducts.
Aqueducts are effective at moving water from places that have water to places that need water. Aqueducts built as open canals can lose a large fraction of water through leaks and evaporation. Newer aqueducts are commonly built as pipelines to reduce water loss, but they still require a large amount of resources to construct and their construction can have negative impacts on the habitat during the construction process.
Describe the processes used to convert salt water into fresh water.
The process of converting salt water into fresh water is known as desalination or desalinization. It can be accomplished either through distillation, which boils water and then condenses the salt-
Module 28 Water Use by Humans Now and in the Future
Compare and contrast the four methods of agricultural irrigation.
Furrow irrigation involves flooding the furrows between plant rows; it is the easiest and least expensive method, but it also is the least efficient. Flood irrigation involves flooding an entire field with water; it is only slightly more efficient than furrow irrigation. Spray irrigation involves distributing water through spray nozzles that resemble giant lawn sprinklers; it can be 75 to 95 percent efficient. Drip irrigation involves the use of a hose that slowly drips water on or below the ground surface; its efficiency is over 95 percent.
Describe the major industrial and household uses of water.
About half of the water used for industry is used for generating electricity. Of the remainder, major users include refiners of paper and metal. Of all indoor water use in U.S. households, we use 41 percent for flushing toilets, 33 percent for bathing, 21 percent for laundry, and 5 percent for cooking and drinking. Outdoor water use varies tremendously by region as a result of differences in climate and in the use of water for swimming pools and watering lawns.
Discuss how water ownership and water conservation are important in determining future water availability.
Water ownership is a complicated issue because multiple groups can have a right to use the water but it is often unclear who actually owns the water. Among nations, water rights are often determined through treaties. In some regions of the world, everyone competes for water by purchasing it. The demand from different users helps to determine the price while government oversight can help ensure that there is a proper balance between the needs of industry, agriculture, households, and the environment.