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Understanding Water Use in California and the Sacramento Valley

Monday, Mar 24th, 2014

In water short years, increased attention is paid to how much water is used in the state, where it is used, and for what purposes.  Many different numbers are used to describe water use in the state among generalized water users (environmental, agricultural and urban).  Often, water use is only described in terms of agricultural and urban uses, ignoring the important dedication of water to environmental uses.

The Department of Water Resources’ California Water Plan Update 2013 contains a substantial amount of information regarding water use both in the Sacramento Valley and in the state as a whole.  Chapter 3 in Volume 1 describes the many uses of water on a statewide basis and how those uses vary in different water year types (critically dry, dry, below normal, above normal and wet).

The Water Plan has identified 2010 as the year that most closely resembles an average water year in California.  According to the Water Plan:

 “California, in an average water year like 2010, receives nearly 200 million acre-feet of water from precipitation and imports from Colorado, Oregon, and Mexico. Approximately 50 to 60 percent of this total supply is used by native vegetation, evaporates to the atmosphere, provides some of the water for agricultural crops and managed wetlands (referred to as effective precipitation), or flows to Oregon, Nevada, the Pacific Ocean, and salt sinks like saline groundwater aquifers and the Salton Sea. The remaining 40 to 50 percent, identified as dedicated or developed water supplies, as shown in the Figure 3-11 and Table 3-2, is distributed among urban and agricultural uses for protecting and restoring the environment, or as storage in surface water and groundwater reservoirs for later use. In any year, some of the dedicated supply includes water that is used multiple times (reused water) and water that is held in storage from previous years. Ultimately, about one-third of the dedicated supply flows to the Pacific Ocean or to other salt sinks, in part to meet environmental water requirements for designated Wild and Scenic Rivers and other environmental requirements and objectives.”  (California Water Plan Update 2013, Public Review Draft, pg. 3-16)

 Statewide Water Use

The information below is from Water Year 2010 contained in Table 3.2 of the Water Plan.  Overall water use in the state was divided among beneficiaries in the following manner:

In 2010, “applied water” use (water applied to provide a beneficial use) in California was approximately 79.8 million acre-feet.  The “depleted water” use (water that was consumed and not available for other uses) was 58.3 million acre-feet.

Statewide applied water uses:

Urban – 8 million acre-feet, or 10% (8 maf/79.8 maf total applied water)

Irrigated agriculture – 33.1 million acre-feet, or 41.5%

Environmental* – 38.7 million acre-feet, or 49% (includes 1.5 maf for managed wetlands, 5.3 maf for required Delta outflow, 6.8 maf for instream flows, and 25.1 maf for Wild and Scenic Rivers)

*Includes managed wetlands, required Delta outflow, instream flows, and Wild and Scenic Rivers

Statewide depleted water uses:

Urban – 5.2 million acre-feet or 9% (5.2 maf/58.3 maf total depleted water)

Irrigated agriculture – 23.9 million acre-feet, or 41%

Environmental – 29.2 million acre feet, or 50%

Sacramento River Hydrologic Region Water Use

Volume 2 of the California Water Plan 2013 includes water use information from the hydrologic regions in the state, including the Sacramento River Hydrologic Region.

As mentioned above, the California Water Plan has identified 2010 as the year that most closely resembles an average water year in California.  The information below is from Water Year 2010 contained in Figure SR14 of the Sacramento River Hydrologic Region chapter of Volume 2.

In 2010, “applied water” use (water applied to provide a beneficial use) in the Sacramento River Hydrologic Region was approximately 21.5 million acre-feet.  The “depleted water” use (water that was consumed and not available for other uses) was 12.824 million acre-feet.

In the Sacramento River Hydrologic Region, the percentage of water dedicated to the environment is much greater than the statewide average.  Overall water use in the Sacramento River Hydrologic Region was divided among beneficiaries in the following manner:

Sacramento River applied water uses:

Urban – 889,000 acre-feet, or 4.14%

Irrigated Agriculture – 7.942 million acre-feet, or 36.94%

Environmental – 12.668 million acre-feet, or (includes 602,000 af for managed wetlands, 5.323 maf for required Delta outflow, 3.622 maf for instream flows, and 3.121 maf for Wild and Scenic Rivers)

Sacramento River depleted water uses:

Urban – 491,000 acre-feet, or 3.83%

Irrigated Agriculture – 4.723 million acre-feet, or 36.83%

Environmental – 7.61 million acre-feet, or 59%

 Conclusion

This year, unless there are dramatic increases in rainfall throughout the state, we will experience unprecedented water shortages.  Because of this, water uses in the state will differ greatly from what we are used to.  That being said, it is important to understand how water is used in the Sacramento Valley and throughout the state and recognize all uses of water to ensure that water management is occurring in a responsible and informed manner.  In a water short year this is especially important.

 

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