Keywords:Central Valley, Groundwater Exchange, groundwater pumping impacts, Groundwater Sustainability Plan (GSP), Sustainable Groundwater Management Act (SGMA)
The Sacramento River Hydrologic Region (see Figure SR-1 includes the entire California drainage area of the Sacramento River (the state’s largest river) and...
The Sacramento River Hydrologic Region (see Figure SR-1 includes the entire California drainage area of the Sacramento River (the state’s largest river) and its tributaries. The region extends from Chipps Island in Solano County north to Goose Lake in Modoc County. It is bounded by the Sierra Nevada on the east, the Coast Ranges on the west, the Cascade and Trinity mountains on the north, and the Sacramento-San Joaquin River Delta (Delta) on the south. The Sacramento River Basin actually begins in Oregon, north of Goose Lake, a near-sink that intercepts the Pit River drainage at the California-Oregon border.
Some key issues for this region are summarized here and discussed further later in this report.
Agriculture. Between 2005 and 2010, the region supported about 1.95 million acres of irrigated agriculture on average. Approximately 1.58 million acres is irrigated on the valley floor. The surrounding mountain valleys add about 370,000 irrigated acres to the region’s total — primarily as pasture and alfalfa. The gross value of agricultural production in the Sacramento Valley for 2011 was about $4.1 billion (California Department of Food and Agriculture 2013). Rice and walnuts are the highest grossing crops in the region followed by almonds and tomatoes. The direct, indirect, and induced effects of the agricultural industry to the regional economy are discussed in this report.
Groundwater. With a 2005-2010 average annual extraction volume of 2.7 million acre-feet (maf), groundwater pumping in the Sacramento River Hydrologic Region accounts for 17 percent of all the groundwater extraction in California — the third highest among the 10 hydrologic regions in California, behind Tulare Lake Hydrologic Region with 38 percent and San Joaquin River Hydrologic Region with 19 percent of the total. Overall, groundwater contributes to about 31 percent of the total water supply. Most groundwater extraction in the region occurs for agricultural water use (2.4 maf), meeting about one-third of agricultural water demands. Groundwater extraction for urban water use is significantly less (465 thousand acre-feet [taf]), which meets about half of the urban water needs. Groundwater levels for much of the region have declined from 2005 to 2010. Groundwater level declines ranging from 20 to 30 feet are seen in the northwestern portion of the Sacramento Valley Groundwater Basin. Declines ranging from to 10 to 20 feet are seen in the northern, the mid- to south-western, and the southeastern portions of the valley. For the rest of the Sacramento Valley Groundwater Basin and the Redding Area Groundwater Basin, groundwater level declines have
ranged from zero to 10 feet.
Flood. Exposure to a 500-year flood event in the region threatens approximately one in three residents, almost $65 billion in assets (crops, buildings, and public infrastructure), 1.2 million acres of agricultural land, and over 340 sensitive species. Almost 95 percent of Sutter County residents, more than 55 percent of Yuba County and Yolo County residents, and more than 50 percent of agricultural land region-wide are exposed to the 500-year flood event.
Climate Change. Several different climate regions overlie portions of the Sacramento River Hydrologic Region. Air temperature data collected for the past century has been summarized by the Western Regional Climate Center (WRCC) for the different regions which are outlined below.
The region also is currently experiencing impacts from climate change through changes in statewide precipitation and surface runoff volumes, which in turn affect availability of local and imported water supplies. During the last century, the average early snowpack in the Sierra Nevada decreased by about 10 percent, which equates to a loss of 1.5 maf of snowpack storage (California Department of Water Resources 2008). Projections and impacts based on modeling of climate change are included in this report.
California’s agriculture sector has exceeded expectations during the most severe drought in recorded history at the cost of massive but unsustainable groundwater pumping....
California’s agriculture sector has exceeded expectations during the most severe drought in recorded history at the cost of massive but unsustainable groundwater pumping. Continued groundwater overdraft, while reducing the economic impacts of the drought for the agricultural sector now, has shifted the burden to others, including current and future generations forced to dig deeper wells, find alternative drinking water sources, and repair infrastructure damaged by subsidence. That is the conclusion of the new study, Impacts of California’s Ongoing Drought: Agriculture, released today by the Pacific Institute, an independent global water think tank.
This new study is the first comprehensive analysis of the actual impacts of the drought on California agricultural revenue and employment through 2014 – the last year for which data are available. The study, drawing on data from the USDA National Agricultural Statistics Survey and the California Employment Development Department, analyzes acreage, revenue, and employment figures from 2000-2014. Production costs, impacts on animal or nursery products, or regional impacts are not examined because these data are not yet available. The study’s results provide critical insight into how the state can maintain a healthy agriculture sector in a future likely to see less water, more extreme weather, and greater uncertainty.
California remains the largest agricultural producer in the U.S. in total output and in exports. During the drought, California’s agriculture sector has experienced record-high crop revenue and employment. Last year farmers harvested 640,000 fewer acres, which was 9 percent below pre-drought levels, yet crop revenue remained strong. Indeed, crop revenue peaked in 2013 at $34 billion – the highest level in California history. In 2014, crop revenue declined by $480 million, representing a 1.4 percent reduction from 2013 levels. All economic estimates have been corrected for inflation. Statewide agriculture-related jobs also reached a record-high of 417,000 people in 2014, highlighting the sector’s ability to withstand the reduction of available water.
Sea level rise, large-scale flooding, and new conveyance arrangements for water exports may increase future water salinity for local agricultural production in California’s...
Sea level rise, large-scale flooding, and new conveyance arrangements for water exports may increase future water salinity for local agricultural production in California’s Sacramento–San Joaquin Delta. Increasing salinity in crop root zones often decreases crop yields and crop revenues. Salinity effects are nonlinear and vary with crop choice and other factors including drainage and residence time of irrigation water.
Here, we explore changes in agricultural production in the Delta under various combinations of water management, large-scale flooding, and future sea level rise. Water management alternatives include through-Delta water exports (current conditions), dual conveyance (through-Delta and a 6,700 Mm3 yr?1 [or 7500 cfs] capacity peripheral canal or tunnel) and the flooding of five western islands with and without peripheral exports. We employ results from previous hydrodynamic simulations of likely changes in salinity for irrigation water at points in the Delta. We connect these irrigation water salinity values into a detailed agro-economic model of Delta agriculture to estimate local crop yield and farm revenue losses.
Previous hydrodynamic modeling work shows that sea level rise is likely to increase salinity from 4% to 130% in this century, depending on the increase in sea level and location. Changes in water management under dual conveyance increase salinity mostly in the western Delta, and to a lesser extent in the north, where current salinity levels are now quite low. Because locations likely to experience the largest salinity increases already have a lower-value crop mix, the worst-case losses are less than 1% of total Delta crop revenues. This result also holds for salinity increases from permanent flooding of western islands that serve as a salinity barrier.
Our results suggest that salinity increases could have much smaller economic effects on Delta farming than other likely changes in the Delta such as the retirement of agricultural lands after large-scale flooding and habitat development. Integrating hydrodynamic, water salinity, and economic models can provide insights into controversial management issues.
Agricultural drainage problems in California’s San Joaquin Valley have been a threat to the environment and to agriculture for at least the last...
Agricultural drainage problems in California’s San Joaquin Valley have been a threat to the environment and to agriculture for at least the last forty years. Though some improvements have been made, inaction - not progress - has been the most characteristic result of efforts to deal with the problem.
A recent federal appeals court ruling has focused the debate by establishing that there is no legal mandate to build the San Luis Drain and granting the federal government discretion to propose the best means of providing drainage service. This Briefing Book explores opportunities to break the decades-old political logjam and proposes a strategy for making long-needed progress on the agricultural drainage problem in the San Joaquin Valley.