How dry is it? Look at these three charts from the Department of Water Resources.
This is the driest year on record in terms of precipitation in the Tulare Basin.
In the San Joaquin Basin, it is a little better. It is the second driest year in terms of precipitation.
In the Northern Sierra, it is also the second driest in history.
Evapotranspiration Results: One of the needs of a Groundwater Sustainability Agency in implementing their plans is to obtain water consumption data. Historically, water flow meters on individual wells have been the method by which groundwater extraction has been determined. However, water meters can tell you how much water was applied, but they do not tell you how much was consumed by the plant and how much returned to the ground. Over the past number of years remote sensing technology using satellite imagery has been improved to a point where the water consumed by plants can be accurately tracked by measuring the amount of evapotranspiration (Etc.) coming off the field. Once you know how much water the plant consumed, then you back out any surface water that was applied to the field and any precipitation that may have fallen and what you are left with is how much groundwater was consumed to grow that crop.
Pixley and Lower Tule Irrigation Districts did pioneering work on this technology with the IRTC program of Cal Poly for several years, even prior to the passage of SGMA. More recently these two districts hired Land IQ, a private company that has created an advanced commercial application of this technology to provide their districts with evapotranspiration derived water consumption data for all the acreage within their districts.
More information about Land IQ and remote sensing can be found here.
Pixley and Lower Tule recently shared the 2020 water consumption results for various farming/cropping operations in their districts (graph is pictured below). This is very interesting data. If there is a field that is double cropped, then you need to add the two crops Etc.’s together to get the total water consumed off that acre during 2020. So, a wheat crop consumed 1.62-acre feet and that would add to the consumption of a corn crop at 2.57 for a total consumed by that double cropped acre of 4.19-acre feet. You might also notice the Etc. reading from the dairy footprint, both open lot and free stall. One point to remember about the Etc. coming off of the dairy footprint is that in addition to groundwater supplies that are used on that dairy footprint, there is a lot of moisture that is imported to the dairy footprint in the feed that is delivered and consumed by the animals.
This drought has attracted a lot of media and political attention. Clearly there are impacts to water levels and wells as farmers turn to groundwater to provide the irrigation needed to grow their crops. The State Water Resources Board made news this week by announcing their intention to issue curtailment orders to junior surface water right holders. The State Board has regulated surface water through a permit program for decades. Part of that program is enforcing the water rights system in times of shortage. Clearly there are concerns about how these orders will impact certain farmers, but there is not enough water to go around and there is a priority system to deal with this circumstance. It is not unusual for California to have dry years. Yes, this is a particularly dry year. Let us hope the public and politicians learn from this that you must prepare in the wet years for the inevitable dry years.
Geoff Vanden Heuvel
Director of Regulatory and Economic Affairs