Water Unit 8

Chapter 20.1 Residential use The average person in the U.S. Uses 300L of water daily. Half is used for personal hygiene and the other half is used for outside use.

Industrial Use 44% of all water is used by industry. It is used for transporting goods, disposing of wastes, power sources and coolants. Availability of water is a large factor on where a factory will locate.

Agricultural Use The farming industry is the single largest user of water in the U.S. Irrigation is the process of bringing water to an area for use in growing crops. This uses 200 billion liters each day.

Types of Irrigation Some question the use of scarce water supplies for irrigation. 1.) Flood irrigation – this floods flat land with water. It is very wasteful some goes into soil with no crops and half is evaporated.

2.) Furrow Irrigation – this releases water into ditches or furrows dug between crops. Evaporation rate is high and mineral salts accumulate. 3.) Overhead Irrigation – sprinkler systems are most commonly used for flat grounds and uneven slopes.

4.) Subirrigation – Water is introduced naturally or artificially underground.

Effects of Human Water Uses The building of dams, draining of swamps, changing of stream courses, and the removal of water from natural sources all adversely affect wildlife.

20.2 Water Resources Surface water is water above the ground in streams, lakes, and ponds. The water resulting from rainfall and melting ice that travels along the ground is called runoff.

If runoff occurs in a natural area it creates rills. These rills deepen and connect forming streams. Surface water can also form from a stream passing a deep fault.

Aquifers Water that does not runoff seeps into the ground into the bedrock forming groundwater. The area that separates the ground from the water is called the water table. The area of saturated rocks right below the water table is called the zone of saturation.

The area where water seeps through the soil is called the zone of aeration. Then the area where ground water meets a depression is called the zone of discharge. Aquifers do not move at a constant rate.

Problems When a body of water is drained faster than it is filled, it causes an overdraft*. Overdraft causes two problems:

1.) Saltwater intrusion – in coastal areas the pressure from freshwater aquifers keeps out the salt water. If overdraft occurs it the saltwater can intrude.

2.) Subsidence – the collapse of an aquifer.

Decrease in Freshwater It is predicted that the largest aquifer in the U.S will run dry in the next forty years. The loss of freshwater is harmful to all organisms.

20.3 Water Treatment Many developed countries treat water removing impurities. Tap water in many places is considered unsafe: parts of Mexico, South America, China, and Africa.

Removing Salts Desalination* – the process by which salts are removed from water. There are three desalination methods 1. distillation – the water is heated to boiling when it evaporates it leaves the salt behind. Then the water vapor is cooled to turn it back into water.

2. Reverse osmosis – the water is sent through a strainer with tiny pores. These pores are big enough to let water through and too small for salt. 3. Freezing – the water is frozen separating the water into ice and brine slush. The ice contains the majority of the freshwater.

Water Purification Water purification is the removal of harmful chemicals and microorganisms. It involves the following processes:

Sedimentation and filtration – the water is first passed through screens, then it is placed in a holding tank. The large particles settle to the bottom. Then a coagulant is added to clump the smaller debris. Then the sediment is removed and the water is passed through a sand filter that catches the remaining particles.

Aeration and Sterilization Sometimes particles may be too small or dissolved gases may be present in water. Aeration is exposing water to the air. This can be done by spraying water or letting it flow. This allows bacteria to break down the organic material.

Sterilization Any harmful organisms added during aeration can be killed by exposing them to extreme heat or chemicals (mostly chlorine and ozone). Ozone is more effective than chlorine, but it has to be refrigerated and it can only be stored for a limited time.

Chlorine and Ozone are both dangerous at high levels Chlorine and Ozone are both dangerous at high levels. Some studies suggest that chlorine may produce other harmful chemicals.

Water Pollution Water pollution first became a problem when cities became larger and dumped their waste into nearby waterways.

A sewage treatment facility processes raw sewage before it is dumped into surface water systems. Some of facilities can release raw sewage into waterways if over flooded.

Pathogens Parasites, bacteria, and viruses that cause diseases in living things. Anyone who comes in contact with contaminated water may become infected. (Ex: Malaria)

Types The main two types of water pollution are runoff and sewage. All pollutants can disrupt aquatic ecosystems and many are threats to human health. (Plastics)

Chemical Pollutants Toxic chemicals – elements and compounds that are directly harmful to living things. Two types:

1. ) inorganic chemicals – elements or compounds that lack carbon 1.) inorganic chemicals – elements or compounds that lack carbon. It includes acids, salts, heavy metals, and plant nutrients.

Heavy metal – a metallic element with a high mass number. Ex Heavy metal – a metallic element with a high mass number. Ex. Mercury, lead, cadmium, nickel, and chromium. Tailings from mining are large contributors to heavy metal run off and leaching.

2.) Organic Chemicals Derived from living organisms, that contain carbon. They can either come from living things or be made in a laboratory. Synthetic materials include gasoline, oils, plastics, pesticides, and fertilizers. Crude oil is one of the most dangerous and common organic pollutants. (Exxon Valdez)

Eutrophication Water systems need nutrients such as solid and liquid animal waste, nitrates, nutrients, and phosphates, but at high doses they can act as a pollutant.

The abundance of nutrients leads to large amounts of plant growth that eventually choke each other out. This causes an abundance of bacteria, that lowers the amount of oxygen in the water system.

Thermal Pollution This is a large increase in water temperature due to power plants and other industrial facilities. A lot of factories use water cooling systems to reduce the amount of heat.

Increased temperature raises the amount of oxygen fish need. Raised temperature also determines the amount of dissolved oxygen in water.

21-4 Controlling Water Pollution The first U.S. legislation passed to address water pollution was the Rivers and Harbors Act of 1899. There has been numerous legislations passed since then due to weak laws or lack of enforcement.

In 1972 Congress passed the Federal Water Pollution Control Act In 1972 Congress passed the Federal Water Pollution Control Act. This was an attempt to set the standard for all fifty states. It unfortunately is only a vision of water quality standards. Overall U.S. water systems are showing improvement.

Discussion How can we manage biodiversity, economic stability, and human recreation of different bodies of water? Colorado River