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Let's Examine the Issues: Water Quantity and Quality - March 13, San Francisco

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Because water is such a vital resource, it is important to understand where water comes from, how much is available, and how to ensure that we will have enough drinkable water in the future.

  • 70% of the Earth’s surface is covered by water.
  • 97% is in the oceans and is undrinkable without desalination treatment.
  • Less than .5% of the planet’s freshwater is surface water.
  • Most freshwater is glacial ice or is trapped underground.

The Bay Area gets water from a variety of sources. A large portion of the Bay Area’s water comes from the Hetch Hetchy reservoir in Yosemite National Park. This reservoir collects water from the 459 square-mile Tuolumne River watershed, fed by snowmelt from the Sierra Nevada Mountains. Other sources of water for the Bay Area include…

  • groundwater (water that naturally collects underground)
  • surface water (collected rain and snow melt, lakes, streams and rivers)
  • recycled water (treated wastewater)

California’s water is distributed among urban consumption, agriculture, and the environment according to the pie chart below.

  • Urban water uses include everything from personal uses such as drinking, watering the garden, and bathing to industrial use.
  • Agricultural water use is important in California as the state produces over 250 different crops and leads the nation in production of 75 commodities.
  • Environmental water includes wild and scenic river flows, required Delta outflow, and wetland water and is crucial for maintaining intact marine ecosystems.

Having enough water for urban, agricultural and environmental purposes is crucial, but so is making sure that water is clean and safe. Although much of the area’s drinking water is high quality, there are regions in the Bay Area that get water from less pristine sources with contamination issues.

  • Water from the Hetch Hetchy reservoir is considered to be some of the country’s highest quality drinking water and does not have to be filtered before use because it is so pristine.
  • Over 20 million people from multiple Bay Area counties get their drinking water from the Sacramento-San Joaquin River Delta, which experiences influxes of pesticides, industrial discharge, treated sewage and other forms of pollution.

According to a recent study by U.S. PIRG that analyzed 2005 compliance with the Clean Water Act, California was one of the10 states with the greatest number of facilities leaking pollutants beyond the legal limits and was the state with the most large-scale violations.

  • The Clean Water Act has led to a cleaner bay by decreasing the amount of organic waste and nutrients.
  • The San Francisco Bay is still being polluted by urban runoff, agricultural runoff, and deposition from the atmosphere.
  • Many Bay Area cities, including San Francisco, South San Francisco and Sausalito, exceeded their permits to discharge pollutants into local waterways.
  • Pollutants released into the bay include mercury, fecal matter and cyanide.

The Bay Area is already dealing with water quantity and quality issues, but because of the future threats of climate change and population increase, both water quantity and water quality may be compromised in the near future. Climate change is expected to increase temperatures, raise sea levels and change precipitation and runoff patterns. These changes are likely to lead to decreased snow pack and the storage it provides during the late summer months, more variable precipitation, and extreme weather events such as floods and droughts. All of these changes will impact the Bay Area’s ability to get both the quantity and quality of water it needs.



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