Think about where water comes from. Is there more or less water on Earth than there was one billion years ago? Properties of Water The Chemistry of Water

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.

Objectives Identify patterns of global water use. Explain how water is treated so that it can be used for drinking. Identify how water is used in homes, in industry, and in agriculture. Describe how dams and water diversion projects are used to manage freshwater resources. Identify five ways that water can be conserved.

Water Resources  Water is essential to life on Earth. Humans can live for more than a month without food, but we can live for only a few days without water.  Two kinds of water found on Earth:  Fresh water, the water that people can drink, contains little salt.  Salt water, the water in oceans, contains a higher concentration of dissolved salts.  Most human uses for water, such as drinking and agriculture, require fresh water.

The Water Cycle  Water is a renewable resource because it is circulated in the water cycle.  In the water cycle, water molecules travel between the Earth’s surface and the atmosphere. Water evaporates at the Earth’s surface. Water vapor rises into the air. As the vapor rises, it condenses to form clouds. Eventually the water in clouds falls back to the Earth in the form of precipitation.  The oceans are important because almost all of the Earth’s water is in the ocean.

Transpiration (evaporation of water through plant leaves) Infiltration (water enters soil)

Global Water Distribution  71% of the Earth’s surface is covered with water  nearly 97% is salt water in oceans and seas Of the fresh water on Earth:  about 77% is frozen in glaciers and polar icecaps  22% ground water  small percentage is liquid fresh water that humans can use

What does this mean???  If we had 100 drops of water, how many drops would be fresh water?  Only 3!  Of those 3 drops of water, how many would be frozen in glaciers and polar ice caps?  About 2.3!  The remaining 0.7 of a drop is what is available for all 7.2 billion humans in the world to use for everything they need water for – drinking, cooking, bathing, cleaning, watering, flushing toilets, industry, etc.!!!

Surface Water  the water that is on the surface of the Earth  all the bodies of fresh water, salt water, ice and snow that are found above the ground  played a vital role in the development of human societies - cities and farms built near reliable sources of water

River System  a flowing network of rivers and streams draining a river basin  largest - Amazon River system – covers 2/5 ths of South America and drains an area of land nearly the size of Europe

Watershed  the area of land that is drained by a water system  varies throughout the year - rapidly melting snow & spring and summer rains can increase the amount of water in a watershed What Is A Watershed?

Watersheds

Groundwater  the water that is beneath the Earth’s surface  percolates through the soil and down into the rocks beneath  water table - level where the rocks and soil are saturated with water

Aquifers  rock or sediment that stores groundwater  an important water source for many cities  most aquifers consist of materials such as rock, sand, and gravel that have a lot of spaces where water can accumulate  groundwater can also dissolve rock formations, filling vast caves with water, creating underground lakes

The Recharge Zone  an area in which water enters an aquifer  any pollution in the recharge zone can also enter the aquifer  buildings and parking lots can reduce the amount of water entering an aquifer  recharge zones need to be carefully managed - surface water can take a very long time to refill an aquifer, even tens of thousands of years

The Recharge Zone

Wells  hole that is dug or drilled to reach groundwater  ground water may be a more reliable source of water than surface water  water is filtered and purified as it travels underground

Water Use and Management  When a water supply is polluted or overused, everyone living downstream can be affected.  A shortage of clean, fresh water is one of the world’s most pressing environmental problems.  According to the World Health Organization, more than 1 billion people lack access to a clean, reliable source of fresh water.

Global Water Use There are three major uses for water: residential use, agricultural use, and industrial use.

Residential Water Use  Households  8% of all water used  differences in residential water use throughout the world:  average person in the US uses about 300 L of water/day  average person in India uses only 41 L of water/day

Residential Water Use  In the U.S., only about half of residential water use is for activities inside the home, such as drinking and cooking.  Remainder of the water used residentially is used for activities outside the home such as watering lawns.

Water Treatment  includes both physical and chemical treatment  Potable - suitable for drinking  Water treatment removes elements such as mercury, arsenic, and lead, which are poisonous to humans even in low concentrations.  pathogen – virus or bacteria that causes disease - found in water contaminated by sewage or animal feces but can be removed with water treatment

Drinking-Water Treatment Water and You: The Water Treatment Process

Industrial Water Use  19% of water used in the world  used to manufacture goods, to dispose of wastes, and to generate power  mostly used to cool power plants

Agricultural Water Use  67% of all water used in the world - crop irrigation  in US - high-pressured overhead sprinklers are the most common form of irrigation - inefficient because almost 50% of water evaporates & never reaches plant roots

Water Management Projects  designed to meet the needs of people living where supply of water is inadequate  dam - a structure that is built across a river to control it’s flow  reservoir - an artificial body of water that usually forms behind a dam  Water management projects can have various goals, such as brining in water to make a dry area habitable, creating a reservoir for drinking water, or generating electric power, which then allows people to live and grow crops in desert areas.

Impacts  entire ecosystems can be destroyed  communities displaced  poor soil quality downstream  dam bursting can kill people living along the river below Teton Dam Disaster

Water Conservation  As water sources become depleted, water becomes more expensive.  This is because wells must be dug deeper, water must be piped greater distances, and polluted water must be cleaned up before it can be used.  Water Conservation is one way that we can help ensure that everyone will have enough water at a reasonable price.

Water Conservation in Agriculture  water loss comes from evaporation, seepage, and runoff  Drip irrigation systems deliver small amounts of water directly to plant roots by using perforated tubing. Water is released to plants as needed and at a controlled rate.

Water Conservation in Industry  recycling of cooling water and wastewater  In an innovative program, Denver, Colorado pays small businesses to introduce water conservation measures. This not only saves money for the city and the business but also makes more water available for agricultural and residential use.

Water Conservation at Home  changing a few everyday habits  using only the water that they need  using water-saving technology, such as low-flow toilets  water lawns at night to reduce the amount of evaporation  xeriscaping - designing a landscape that requires minimal water use.

Solutions for the Future In some places, conservation alone is not enough to prevent water shortages, and as populations grow, other sources of fresh water need to be developed.

Desalination  the process of removing salt from ocean water  dry and hot countries (ex. Middle East)  desalination plants heat salt water and collect the fresh water that evaporates  uses a lot of energy and is too expensive for many nations to consider

Transporting Water  water can be transported from other regions  towing enormous plastic bags full of fresh water  bag solution is being considered in the United States, where almost half of the available fresh water is in Alaska  icebergs - an efficient way to tow icebergs has not been discovered yet