Water
7.0 Module Learning Objectives
After completion of this module, you will be able to:
Understand that the fresh water we use every day is a finite resource that we must conserve.
Recognize the importance of the water cycle and how climate change is affecting it.
Acknowledge the complex systems that were built to deliver water to our homes and businesses.
7.1 How much water is there on earth?
The video on the left shows blue spheres representing relative amounts of earth's water in comparison to the size of the earth. The largest sphere represents all water on, in, and above the earth.
The smaller sphere represents all of earth's liquid freshwater. Freshwater sources include surface waters from streams, rivers, and lakes and groundwater which is found below earth's surface. Much of this groundwater is deep in the ground, unavailable for humans to access.
The tiny sphere represents all the freshwater that is in a form or a location that is easily accessible to humans. This video serves as a reminder that water resources are finite and we must conserve water as much as possible.
7.2 Where is all of earth's water?
Image 7.1 The bar graphs above illustrates where all of earth's water is found. Around 97% of all the water on earth is in the oceans and only around 3% of all the water on earth is freshwater. Humans cannot drink ocean water because of its salinity, which means we all must share the mere 3% of freshwater sources for survival.
Of that 3%, most freshwater is stored in glaciers and ice caps, 30% is groundwater, and a mere 1.2% is surface water and other freshwater sources. Of that 1.2%, 69% of freshwater is in ice and permafrost, 21% is in lakes, and the rest is divided up between the atmosphere, living things, rivers, swamps and marshes, and soil.
7.3 Water Footprints
Image 7.2 The graph above shows how water footprints vary dramatically between countries. In the United States, each person uses around 2,200 gallons of water per day, whereas in Bangladesh each person uses around 550 gallons of water per day. A country's water footprint is based on the consumption habits of its citizens, the country’s climate and water-use practices.
Everything we buy, use, wear, and eat takes water to make. We rely on both domestic water sources and international water resources to manufacture and produce the goods we rely on every day, like fuel for our cars, plastic bottles, and clothes. A water footprint is a measurement of the volume of domestic and international water used to produce these goods. A water footprint can be used to measure the volume of water consumed to produce practically any item, from food and clothes to cars and textiles. It can also tell us how much water is being consumed by a specific country or how much is being consumed from a specific river basin or from an aquifer.
The water "hidden" in traded agricultural commodities like beef, vegetables, rice, etc., is called virtual water. For example, a single pound of beef takes an average of 1,800 gallons of water to produce. This is because it takes an extremely large amount of water to produce the massive amounts of grass, forage and grain it takes to feed cattle. A person's diet accounts for more than two thirds of their own total water footprint, mostly because of all the virtual water needed to produce our food.
Image 7.3 The table above shows the water footprint for common food items. Notice it takes an average of 674 gallons of water to produce just one 6 ounce steak and 660 gallons of water to produce one hamburger! Pound for pound, meat has a bigger water footprint than vegetables, grains and beans.
7.4 The Water Cycle
The water cycle describes the natural process of how water circulates on, above and below earth’s surface. Water evaporates from earth’s oceans, lakes and streams, rises into the atmosphere, cools and condenses into rain or snow in clouds, and falls again to the surface as precipitation. The water falling on land collects in rivers, streams and lakes, sinks through sediment and into underwater aquifers, flows back into the oceans, and the cycle begins again. The water cycle determines much of the weather patterns on earth.
7.5 Where does the Bay's water supply come from?
The Bay Area relies on various water sources, including local surface water, groundwater, the State Water and Central Valley Projects, water imported from the Sierra Nevadas, water transferred within the region, and water reuse. Some of these water sources are described in more detail below. It is important to note that as climate change continues to disrupt weather patterns and increase the unpredictability of water availability from these sources, we all have a role to play to ensure future generations have access to these water sources.
The Central Valley Project and the State Water Project
Image 7.4 The Sacramento and San Joaquin Rivers and their many tributaries come together in an inland delta just east of San Francisco Bay. Two-thirds of Californians use Delta water, which is made possible by two major water delivery systems, the State Water Project and the Central Valley Project.
The Central Valley Project (CVP) is a federally-funded system of 20 dams, 11 power plants, and 500 miles of canals, conduits and tunnels that run from Lake Shasta in Northern California all the way down to Bakersfield. It is one of the largest water transportation systems in the world, and provides water for 2.5 million Californians and more than 3 million acres of farmland.
The State Water Project (SWP) is a state-funded system that draws water from many of the same sources as the CVP. In contrast to the CVP, the SWP delivers about 70% of its water to California residents (including water for approximately 25 million users in the San Francisco Bay, Central Valley, and Southern California); the remaining 30% is used for irrigation.
80% of the City of Livermore’s water is from the State Water Project. Snowmelt from the Sierra Nevada mountains flows downstream into the California Delta, and then makes its way to the Tri-Valley area through the South Bay Aqueduct. The remaining 20% of the Tri-Valley's water supply is from Del Valle Reservoir and the local groundwater basin.
The Hetch Hetchy Reservoir
Image 7.5 Another major source of water in the Bay area comes from the Hetch Hetchy Reservoir, located in the northwest section of Yosemite National Park on the Tuolumne River. The Hetch Hetchy Reservoir is not a part of the CVP or the SWP, but owned by the city of San Francisco and provides water to 2.4 million people in San Francisco, Santa Clara, Alameda and San Mateo counties. Snowmelt from the Sierra Nevadas feeds the reservoir and transports water 160 miles via gravity from Yosemite to the Bay Area. Hayward, San Francisco, East Palo Alto, and Burlingame get 100% of their water from the Hetch Hetchy Reservoir. Other cities in the Bay area also get some or most of their water from the Hetch Hetchy Reservoir.
The Pardee Reservoir
Image 7.6 The Mokelumne River Watershed in the Sierras flows into the Pardee Reservoir, travels 90 miles through Central California, gets treated at local water plants, and gives residences in Contra Costa and Alameda counties on the East Bay freshwater. The reservoir supplies water to more than 1.2 million people in 22 East Bay cities including Oakland and Berkeley.
Groundwater
Image 7.7 Groundwater fills spaces between soil and rock and collects beneath the earth’s surface in aquifers. As part of the water cycle, groundwater flows from high to low areas, and ultimately discharges into rivers, lakes, or the ocean. Humans tap into aquifers with wells in order to use groundwater. About 20 percent of the Bay Area’s total annual water supply comes from the 35 aquifers in the Bay Area. Groundwater is most heavily used in the Santa Clara, Napa-Sonoma, Livermore, and Petaluma Valleys.
7.6 The World's Water Problem
Climate Change is Altering the Water Cycle
Climate change is significantly altering parts of the water cycle. Because of the complexity of the water cycle, some areas of the world have experienced extreme drought while others have experienced major flooding. As greenhouse gas emissions continue to rise, different regions of the world are expected to experience different water-related disasters.
Higher temperatures are causing water from Earth’s oceans, lakes and rivers to evaporate into the atmosphere quicker. Warmer air in the atmosphere holds more water, which leads to more intense rainstorms and extreme flooding.
During a downpour, rainwater hits pavement and flows into drains, picking up pollutants like oil, fertilizers, and road salts along the way. These pollutants can flow into rivers, streams and groundwater where they can contaminate drinking water.
Image 7.8 Floodwaters trapped a car near the Russian River in Forestville in October of 2021.
Image 7.9 In August 2021, water levels at Lake Oroville remained low due to drought conditions.
Higher temperatures not only cause earth’s surface water to evaporate, but also cause water from earth’s soils to evaporate. Normally when it rains, soils act as sponges and absorb much of the water into underground aquifers. But when soil moisture is lost to evaporation, the land becomes hard and rain is not absorbed. The land continues to dry and leads to more drought.
Future increases in temperature, regardless of whether total precipitation goes up or down, will likely cause longer California droughts, posing major problems for water supplies, natural ecosystems, and agriculture.
Because of warming temperatures, mountain glaciers, Arctic glaciers, and Greenland's ice sheet have decreased drastically in size over the past century. Water from melting glaciers and ice sheets flows down rivers and eventually to the ocean, causing a rise in sea levels.
In the Bay Area, rising sea levels could cause fresh water to become salty, and compromise the water resources we rely on.
Image 7.10 Side-by-side pictures showing the retreat of Bear Glacier in Kenai Fjords National Park, Alaska. The photo on the left was taken October 2012 and the photo on the right was taken September 2019.
7.7 What is CLPCCD doing?
Las Positas College uses reclaimed water for irrigation. Reclaimed or recycled water has been treated, but is diverted to irrigation instead. Because this water already contains minerals, phosphates, etc.; no fertilizers are need on our lawns or landscaping. Using reclaimed water saves valuable drinking water for people and agriculture.
Las Positas College has established rigorous standards for sinks and toilets, etc, that are water efficient.
7.8 Calls to Action
What can you do?
Calculate your water footprint using this link.
Install low-flow WaterSense shower heads in your home.
Go thrift shopping for clothes. It can take 700 gallons of water to produce enough cotton for just one t-shirt.
Only put full loads of laundry in the washing machine.
Give unfinished drinking water to house plants.
Track your water bill to curtail water use.
Obsess over every drop of water.
Install a rain barrel for your house.
Remove your lawn. Lawns require extra water, gas-powered equipment, and fertilizer that pollutes waterways.
Don't drink bottled water.
Only wash your car in a self-serve car wash. A self-serve station use around 12 to 18 gallons of water per vehicle, compared to up to 100 gallons at home.
Find out more ways you can conserve water here.
Use the resources below to educate yourself.
Get Involved
Sign important petitions through Clean Water Action