California WaterBlog

By Spencer Cole

Careful stewardship is key for managing California’s highly sought-after water resources, but a lack of reliable data hampers this goal. That’s beginning to change, however, thanks to two things: technological advances and the passage of the Sustainable Groundwater Management Act (SGMA), which celebrates its 10th anniversary this month. 

SGMA has made waves in the water management space since its passage in 2014. Enacted during a historic drought, the law represents the most comprehensive groundwater regulation ever passed in the state: it requires many of the state’s groundwater basins to bring aquifers into balance by the early 2040s. It also requires that basins work to address “undesirable results” of unsustainable groundwater use—the so-called “six deadly sins”—on their path to sustainability. 

SGMA has also brought about a quiet revolution in the data landscape. Better data collection began before SGMA, of course. Groundwater issues started gaining more traction in the late 2000s, and 2009 saw the creation of the California Statewide Groundwater Elevation Monitoring (CASGEM) program. In the same year, the Water Conservation Act of 2009 was passed, which outlined urban conservation goals and created stricter reporting regulations for agricultural water purveyors. 

But SGMA’s passage took the improvements to a new level. SGMA mandates more data collection and public reporting: under the law, groundwater sustainability agencies (GSAs) are required to draft groundwater sustainability plans (GSPs) detailing local groundwater conditions, which in some areas had not been rigorously tracked before, and the steps they intend to take to reach sustainability. These plans have collected new data on water use and groundwater levels, among other things, and made a wealth of this information available to the public. 

GSAs are also required to provide annual updates on certain data in their plans (e.g. groundwater pumping and changes in aquifer storage) as well as comprehensive updates every five years. In 2017, the state released public records of Well Completion Reports (WCR) data—logging locations and characteristics of groundwater wells as they are drilled—to aid local agencies in protecting groundwater wells.

Technological advances since SGMA’s passage play a major role in improving our understanding of California’s water. For example, remote sensing advances have made it possible to identify where crops are being grown and how much water they are using with much greater accuracy. Similar technologies are allowing researchers to scour the ground for effective places to recharge aquifers (airborne electromagnetic surveying). These leaps in data collection are a boon for researchers and state and local agencies.

Here’s a partial list of some of the new data available, as well as examples of the kinds of analyses it has enabled:

• Water accounting. A recent dataset allows a more detailed look than ever before at water use and outflow in the Sacramento–San Joaquin Delta. But many gaps remain: a new data analysis, for instance, shows that just 8 percent of the state’s streams and rivers have flow gauges.
• Crop mapping. A large percentage of California’s water goes to irrigated agriculture, so it’s important to understand how and where that water is being used. Recent improvements in crop mapping data have helped document the state’s crop mix and how things can shift as climatic conditions change. About half of California’s irrigated lands are now devoted to tree and vine crops; the new data shows where those crops are grown and how they intersect with groundwater management areas. Even during the recent drought (2020–22), for example, the data on irrigated crop acreage showed that perennial crops continued to expand.
• Groundwater overdraft. By 2023, GSPs for all 15 San Joaquin Valley basins had been released, which filled information gaps for basins that previously hadn’t submitted plans. The wealth of data provided in these plans elucidated local water balances and gave us a better understanding of historical overdraft and plans to bring basins into balance in the valley. A similar dataset pieces together information on the water budgets of Sacramento Valley GSPs, as well as plans to address overdraft.
• Surface water deliveries. Recent improvements in surface water deliveries data have helped to refine quantification of local water balances and understand where and for what purposes water is being used. This enabled leveraging the new data to look at SGMA implementation in the San Joaquin Valley through a more detailed lens. 
• Water trading and alternative land uses. Under SGMA, a question continues to loom: what will become of lands that may come out of production to attain groundwater sustainability?  A spatial analysis identified where irrigated lands expected to come out of production might overlap with opportunities for solar energy production, habitat restoration, and less water-intensive cropping. The data revealed abundant opportunities for land repurposing and the analysis addressed some concerns about the implications of water trading for vulnerable communities and farms.
• Groundwater wells. Data from the early years of GSP implementation—coinciding with a historic drought (2020–22)—signaled how the new regulation might be shaping trends in groundwater wells. A newly compiled dataset on new wells and dry wells showed that, compared to the 2012–16 drought, we saw fewer irrigation wells being drilled, more monitoring wells, and similar numbers of domestic well failures. The 2020–22 data reflected dry conditions in Sacramento basins, which had higher rates of well failures and increased groundwater pumping.

These data advances are enabling analyses that would not have been possible ten years ago.  By knowing where water is going in California, decision makers can improve their choices about how to steward this scarce resource. As water managers and agency staff work to adapt to more intense droughts, greater heat, and more intense storms, improved data can help illuminate tradeoffs and drive smarter solutions. 

Spencer Cole is a research associate with the PPIC Water Policy Center. His research interests primarily center around sustainable groundwater management. He holds a BS in environmental engineering and an MS in environmental systems from the Uni
versity of California, Merced.

For more data and information

• Surface water data: State Water Project and Central Valley Project delivery reports, California Data Exchange Center (streamflow, precipitation, snowpack, and  reservoir storage), eWRIMS (water rights database)
• Groundwater data: GAMA (groundwater quality), CASGEM (groundwater levels), Well Completion Reports(groundwater wells), Groundwater Sustainability Plans
• Cropping data: DWR crop mapping, LandIQ (various land use-related datasets), USDA NASS (crop prices and yields), FSA crop insurance reports, OpenET (crop evapotranspiration)
• General reporting: DWR Water Use Efficiency (Agricultural Water Management Plans, Urban Water Management Plans, and farm-gate water deliveries), DWR Water Plan Water Balance 
• Other data: CalEnviroScreen (pollutant exposure)