If you are in California’s Central Valley, you often hear the term “white area” as it relates to farming. It is a description of the area on a map that is not covered with a color. In farming, it usually designates a farm operation that has no surface water for irrigation. Surface water, also known as conveyance water, is river water that has been diverted to canals and transported to an agricultural field.
The map below is from Madera County, California. All the different colored areas are covered by different irrigation districts. An irrigation district is like a water agency that has the infrastructure and contracts to divert water from a river and deliver that water to each of the farms within their area (the colored area).
The white areas of this map are like stranded islands, farms depending on 100% groundwater pumping to irrigate their crops.
Pre-2020-2023, this was not an issue. A farm could and did pump 100% of their crop needs from the groundwater reservoirs. So did the colored areas, when surface water was in short supply like last year (2022).
What has changed post-2020-2023? A California law to stabilize groundwater withdrawals took effect. The Sustainable Groundwater Management Act was adopted in 2014, and details worked at the local level over the last 6 to 9 years are designed to establish sustainable groundwater levels, stop subsidence, improve the quality of the groundwater, and ensure equitable water for all.
When it comes to establishing sustainable groundwater, the local agencies have started to place rules on how much groundwater can be withdrawn by a farm. These amounts run from 1 acre foot down to 0.6 acre foot. Some of the agencies have transitional volumes (temporary volumes) to help the farm plan for the reduction. The transitional volumes with the sustainable volumes together run from 2.5 acre feet down to 1 acre foot.
An almond orchard needs around 4 acre feet of water using traditional surface irrigation and a pistachio tree needs 3 acre feet for water. So, what we are seeing around the valley are trees being removed, because there is not enough groundwater to share among all the growers.
So have a little empathy for our farming neighbors as they work through these challenging times. They are retiring 50% to 75% of their revenue so all Californians can have a stabilized groundwater resource.