On a San Joaquin Valley field, four inches is not much of a water budget. It is also enough, under the right conditions, to put a winter crop on ground that might otherwise sit bare. Small grains do their growing in the cool season, when the calendar is doing some of the irrigation work.
That detail sits at the center of a question now facing growers in the Tulare Subbasin and other water-short parts of the valley: if permanent crops cannot be supported at historic pumping levels, does the next crop have to be no crop at all?
Research from the Public Policy Institute of California describes so-called “SGMA-ready” crops as one alternative to fallowing. The idea is modest rather than miraculous: use crops that require much less water and little additional investment to preserve some farm activity while groundwater use declines. PPIC estimates that as much as 900,000 acres of irrigated farmland in the San Joaquin Valley could contract as the Sustainable Groundwater Management Act takes effect.
A Crop for the Cool Months
The candidates are familiar enough to livestock producers and grain growers: wheat, triticale, barley, oats and rye. UC Davis research summarized by UC Agriculture and Natural Resources finds that these winter grains can be planted during the cool season, rely largely on seasonal rainfall and, when managed properly, grow with as little as four inches of supplemental irrigation.
That timing matters. A winter forage crop does not ask the well to behave like an orchard’s well. It also leaves the grower with a product to market or feed, rather than an idle parcel that still carries taxes, weeds and the ordinary expenses of owning land. The UC Davis work on winter grain crops frames the practice as a way to keep dry-year ground viable without adding substantial pressure to groundwater supplies.
The tradeoff is that low water use does not mean no water use, and a crop that survives on a small irrigation allocation may not produce the same revenue as the crop it replaces. Forage quality, planting windows, seasonal rainfall and a nearby buyer all matter. A field can be agronomically suitable and still be economically awkward.
The Valley’s Hardest Accounting
SGMA makes that accounting unavoidable. Groundwater Sustainability Agencies are expected to bring overdrafted basins into balance by 2040, while growers reduce pumping in places where the aquifer has been doing more work than it can sustain. In the San Joaquin Valley, the Tulare Subbasin faces immediate groundwater challenges, including the consequences of declining water levels and the broader costs of managing a basin with less irrigated acreage.
That is why the crop question is also a finance question. A shift into winter forage may lower irrigation demand, but it does not pay for recharge projects, demand-management programs or subsidence mitigation. Reporting on the PPIC research notes that fewer farmed acres could also leave local agencies with a smaller fee base, while smaller and midsize operations face pressure from rising costs and possible consolidation. Crop shifts are a partial answer, not a valley-wide fix.
For growers, the useful distinction is between land that is temporarily short of water and land whose long-term water account no longer closes. Winter grains may give the first kind of field a productive bridge. They cannot make an overdrafted basin whole, and they do not erase the need for each Groundwater Sustainability Agency to decide how pumping, fees and land use will fit together.