NSW Irrigators’ Council sent a delegation to California for a study tour of water management and irrigation farming. The delegation visited many of the key irrigation regions in the state, through the San Joaquin Valley, Sacramento Valley, and Imperial Valley.
California and Australia (NSW) have many similarities when it comes to water. Both states are all too familiar with extreme climates of droughts, and have well established irrigation regions as a vital part of the economy and livelihoods. Both states are also amidst the implementation of regimes to ensure water use is sustainable. This means that there is valuable opportunity to share lessons and experiences between the states when it comes to managing water. 
Of course, there are also a number of fundamental differences (e.g. in the legal, engineering and political domains, as well as the sheer scale of production).
California is the largest agricultural producing US state, with 70,521 farms, an average farm size of 348 acres, and 24.5 million acres in total agricultural land. The scale of irrigation development is staggering, with significant further development occurring, particularly permanent plantings. Key crops include almonds, grapes, pistachios, dairy, lettuce, strawberries, tomatoes, and walnuts.
In an average year, 40% of California’s irrigation water comes from groundwater, but this can rise to 65% during droughts. The snow in the Sierra Nevada mountains is a key water supply for California. As a general rule, two thirds of California’s water is generated in the north of the State, above Sacramento, and two-thirds of the water use is in the south of the State.
California has developed significant water infrastructure to redistribute water across the state, which has been critical for their economic development, as well as the water security of southern counties such as Los Angeles, Orange County and San Diego. At maximum capacity, the State-owned California Aqueduct can move up to 32,000 megalitres per day, and the federally owned Medota Canal around 11,000 megalitres.
The Metropolitan Water Board is the largest supplier of treated water in the United States, serving approximately 19 million people living in Los Angeles, Orange, Riverside, San Bernardino, San Diego and Ventura counties. The District imports water from the Feather River in Northern California and the Colorado River to supplement local supplies.
Sustainable Groundwater Management Act
Most of the industry organisations and irrigation infrastructure operators whom we met with, reported that the new 2014 Sustainable Groundwater Management Act (SGMA) was their largest concern. That said, it was the largely accepted view that something needs to be done to manage water use sustainably.
Estimates are varied, but it was often quoted that California’s groundwater was being over drawn annually by between 1.8 million to 2.4 million acre/ft (2.2 million to 3 million megalitres).
SGMA is intended to be locally developed with a bottom-up approach, where local level Groundwater Sustainability Agencies (GSA’s) develop the means to meet SGMA requirements. As of late January, 108 GSA’s were required to submit their initial Groundwater Sustainability Plans to comply with SGMA. These plans must lead to a defined degree of sustainability within 20 years.
SGMA is based on avoiding 6 undesirable results – lowering groundwater levels, reduction of storage, seawater intrusion, degraded quality, land subsidence and surface water depletion.
Overall, SGMA is expected to see a 2.4 million acre foot reduction in consumptive water use. For the irrigation community, this will have tremendous impacts. Economic modelling projects that SGMA impacts will involve:
- Fallowed acres: 992,000
- Crop revenue lost: $7.2 billion
- Lost operating income in San Joaquin Valley agriculture: $1.9 billion
- Direct farm job losses: 42,000
- Lost employee income annually: $1.1 billion
- Total job losses:
- 65,000 in the San Joaquin Valley ($1.7 billion in lost employee income)
- 85,000 state-wide ($2.1 billion in state-wide lost employee income)
- (state-wide) lost operating income annually: $3.3 billion
Progress to sustainability is a matter of either increasing the supply of surface water or decreasing demand. Unlike Australia, water rights in California are tied to land, which limits the ability to trade and is a key determinant/limitation in the policy options in moving towards sustainable use. If the full groundwater overdraft was to be met by reducing demand, estimates suggest between 700,000 and 1,500,000 acres might have to be fallowed, out of the existing 6,900,000 acres of irrigation in the critical groundwater areas. Alternatives include increasing surface water by bringing more water down from northern California, and/or utilising “water banking” (aquifer recharge).
Water Banking 
Water Banking – or Managed Aquifer Recharge – involves actively recharging groundwater levels. The Kern Water Bank is a groundwater recharge facility in Kern County which recharges around 600,000 megalitres per year into the aquifer to store for future use. Water Banking has many benefits, including water storage with no/little evaporation loss, improving water security, and replenishing overdrawn aquifers and providing environmental benefits.  It would be of interest for Australia to explore the feasibility of this method.
A number of irrigation farmers, particularly in the rice growing areas, have been working with conservation/environmental groups to manage water, particularly over winter to provide habitat for migrating birds and also for fish nutrient growth. This involves farmers cultivating rice and other crops during the spring and summer, and then providing habitat for wild birds, reptiles and other fauna during the winter.
There has been a dramatic reduction in the population of winter-run chinook salmon making the journey from the Pacific Ocean to the upper reaches of the Sacremento River, from 25,000 in the 1970s to just 2,000 today. Irrigation farmers are actively working to be part of the solution by growing food for fish. This involves flooding rice fields with water, which breaks down the standing rice stalks into food for bugs, which causes a quickly growing bug population providing a nutrient rich diet for fish. This nutrient rich diet, which has 15,000% more fish food than there otherwise would be, which helps to increase the likelihood of young salmon reaching the ocean. This is an excellent example of a positive collaboration between farmers and environmental management.
There is much that we can learn from each other when it comes to water security challenges. We thank our friends at the Farm Water Coalition  for sharing their knowledge and expertise, as well as all the many farmers and water managers whom we met along the way. Many of the challenges for managing water are not unique to Australia, and insights from abroad can provide valuable knowledge on just how far we have come, and what future opportunities exist.
 Of course, there are also a number of fundamental differences (e.g. in the legal, engineering and political domains, as well as the sheer scale of production).