Editing Central Valley (California) (section)

===River engineering===
Sierra Nevada runoff provides one of California's largest water resources. The Sacramento River is the second largest river to empty into the Pacific from the [[contiguous United States]], behind only the [[Columbia River]] and greater than the [[Colorado River]].<ref>The Columbia is the largest, with an average discharge of {{convert|265000|cuft/s|m3/s|abbr=on}}. The Sacramento comes next with a flow of {{convert|30215|cuft/s|m3/s|abbr=on}}, and even though Colorado is much longer, its discharge is only about {{convert|10000|cuft/s|m3/s|abbr=on}} to {{convert|22000|cuft/s|m3/s|abbr=on}} (that is before diversions started; the river is currently dry at the mouth). Other significant rivers include the Klamath {{convert|17010|cuft/s|m3/s|abbr=on}}, Skagit {{convert|16598|cuft/s|m3/s|abbr=on}}, Snohomish {{convert|13900|cuft/s|m3/s|abbr=on}}, and San Joaquin {{convert|10397|cuft/s|m3/s|abbr=on}}.</ref> Combined with the fertile and expansive area of the Central Valley's floor, the Central Valley is ideal for agriculture.<ref>{{Cite news
 |url        = https://www.npr.org/programs/atc/features/2002/nov/central_valley/
 |title       = California's Central Valley
 |publisher   = National Public Radio
 |date        = November 11, 2002 <!-- to 14 -->
 |access-date  = May 27, 2010
 |url-status     = dead
 |archive-url  = https://web.archive.org/web/20101016064558/http://www.npr.org/programs/atc/features/2002/nov/central_valley/
 |archive-date = October 16, 2010 
}}</ref>

The Central Valley is one of the United States' most productive growing regions. This is made possible by engineering the watercourses to prevent flooding during the spring snowmelt and drying up in the summer and autumn.<ref name="CVPhist">{{cite web|access-date=May 27, 2010|archive-date=May 27, 2010|archive-url=https://web.archive.org/web/20100527101033/http://www.usbr.gov/history/cvpintro.html |first=Eric A.|last=Stene|publisher=U.S. Bureau of Reclamation|title=The Central Valley Project: Introduction|url=http://www.usbr.gov/history/cvpintro.html|url-status=dead}}</ref> Many dams, including [[Shasta Dam]], [[Oroville Dam]], [[Folsom Dam]], [[New Melones Dam]], [[Don Pedro Dam]], [[Hetch Hetchy dam|Hetch Hetchy Dam]], [[Friant Dam]], [[Pine Flat Dam]] and [[Isabella Dam]], were constructed on the rivers, with many of them being part of the [[Central Valley Project]].<ref name=" CVPhist"/> These dams impact physical, economic, cultural, and ecological resources: for example, enabling the development of its vast agricultural resources but leading to the loss of the [[Chinook salmon]].<ref>{{cite web|access-date=May 27, 2010|archive-date=May 27, 2010|archive-url=https://web.archive.org/web/20100527112900/http://www.science.calwater.ca.gov/pdf/eco_restor_all_salmon.pdf |publisher=CALFED Bay-Delta Program|title=Ecosystem Restoration: Systemwide Central Valley Chinook Salmon|url=http://science.calwater.ca.gov/pdf/eco_restor_all_salmon.pdf|url-status=live}}</ref>

Post-World War II demand for urban development, most notably the [[San Francisco Bay Area]] and the [[Los Angeles]]/[[Inland Empire (California)|Inland Empire]]/[[San Diego]], required water resources. Moreover, agriculture in the southern Central Valley required far more water than was available locally. The [[Feather River]] in the Sacramento Valley was looked to as a water source, leading to the [[California State Water Project]]. This transports water to the southern San Joaquin Valley and urban areas south of the Tehachapi Mountains.<ref>{{cite web|access-date=May 27, 2010|archive-date=May 27, 2010|archive-url=https://web.archive.org/web/20100527114034/http://www.water.ca.gov/swp/|date=April 15, 2009 |publisher=California Department of Water Resources|title=California State Water Project Overview|url=http://www.water.ca.gov/swp/|url-status=live|work=California State Water Project}}</ref>

Runoff from the Sacramento and San Joaquin Rivers is intercepted in the delta through a series of pumps that divert water into the [[California Aqueduct]], which runs south along the length of the San Joaquin Valley.<ref>{{cite web|access-date=May 27, 2010|archive-date=September 1, 2010|archive-url=https://web.archive.org/web/20100901034636/http://www.water.ca.gov/swp/swptoday.cfm|date=July 18, 2008 |publisher=California Department of Water Resources|title=California State Water Project Today|url=http://www.water.ca.gov/swp/swptoday.cfm|url-status=dead|work=California State Water Project}}</ref> In parallel, pumps divert water into the [[Delta–Mendota Canal]]. The flow of the Sacramento River is further supplemented by a tunnel from the [[Trinity River (California)|Trinity River]] (a tributary of the [[Klamath River]], northwest of the Sacramento Valley) near [[Redding, California|Redding]].<ref>{{Cite news
 |last        = Anderson
 |first       = David
 |url         = http://sunnyfortuna.com/explore/trinity_diversion.htm
 |title       = A temporary diversion
 |work        = Times-Standard
 |date        = July 4, 1999
 |access-date  = May 27, 2010
 |url-status     = live
 |archive-url  = https://web.archive.org/web/20100103225736/http://sunnyfortuna.com/explore/trinity_diversion.htm
 |archive-date = January 3, 2010
}}</ref> Cities of the [[San Francisco Bay Area]], also needing water, built aqueducts from the [[Mokelumne River]] and [[Tuolumne River]] that run east to west across the middle part of the Central Valley.<ref>{{cite web|access-date=May 27, 2010|archive-date=January 10, 2013|archive-url=https://archive.today/20130110152429/http://aquafornia.com/where-does-californias-water-come-from/the-hetch-hetchy-aqueduct|date=August 19, 2008 |publisher=Aquafornia|title=The Hetch Hetchy Aqueduct|url=http://aquafornia.com/where-does-californias-water-come-from/the-hetch-hetchy-aqueduct|url-status=dead}}</ref><ref>{{cite web|access-date=May 27, 2010|archive-date=January 10, 2013|archive-url=https://archive.today/20130110155639/http://aquafornia.com/where-does-californias-water-come-from/the-mokelumne-east-bay-aqueduct|date=August 19, 2008 |publisher=Aquafornia|title=Mokelumne Aqueduct|url=http://aquafornia.com/where-does-californias-water-come-from/the-mokelumne-east-bay-aqueduct|url-status=dead}}</ref>