OPEN ET has Launched

Geoff Vanden Heuvel

Director of Regulatory and Economic Affairs


It may not mean much at first glance, but a consortium of entities including NASA, The U.S. Geological Survey, USDA, as well as a number of academic institutions and NGO’s in conjunction with Google Earth, have produced this powerful web-based information platform that allows you and the world to see how much evapotranspiration (ET) is coming off of YOUR fields. The website address is: https://openetdata.org


I signed on this morning. It is free to create an account and there are some short videos that explain how to use the tool. They also explain ET. Evapotranspiration is the description of what water molecules escape from the land in the form of vapor. This vapor is invisible to eye but can be picked up by satellites and tied back to the field from which it came. ET is not exactly the same as groundwater pumping because the source of the water may be precipitation, or surface water application. But if you know how much water came from precipitation and how much water came from surface supplies and subtract it from the total ET that came off the field, the remaining amount can be safely assumed to have come from groundwater.

What I found on this website is a map that can be zoomed in to the parcel level. You can put the pointer on a specific parcel, and it will tell you how much ET came off the field during the time frame you choose and what USDA says is growing on the field. There is annual data for years 2016 through current. Interestingly, there is no ET from dairy footprint parcels. This is a problem with the ET technology because of the nature of water usage on a dairy getting meaningful ET data from a dairy footprint is difficult. It is clear the OPEN ET database omits information from those parcels.


There are many GSAs with dairies in them that are currently using ET data to track water consumption. Semitropic Water Storage District, Pixley Irrigation District, Lower Tule River Irrigation District, Madera County GSA, both the Madera Subbasin portion and the Chowchilla Subbasin portion, are using ET data in their landowner allocation programs. Recently, Mid Kaweah GSA and Greater Kaweah GSA and East Kaweah GSA announced that they will be implementing an allocation program using ET as a measurement tool. All these GSAs have contracted with private companies that use the ET satellite data but then ground truth that data by using localized weather stations that adjust or interpret those satellite readings to account for the situation on the ground. There is one company, Land IQ, that is doing most of this work. Obviously, they have responded to the roll out of Open ET with some information sheets that answer questions about how the two systems compare. You can access that information here:

Land IQ Frequently Asked Questions

• Land IQ Comparison of Land IQ and Open ET


The Open ET numbers appear to be higher than the ET numbers generated by Land IQ using their ground truthing tools. While ET data is a critical part of the picture on developing a Groundwater Sustainability Plan (GSP), it is important to remember that ultimately the GSPs use groundwater level data to determine whether their plans are achieving the elimination of “undesirable results”. So, a big development this week in the long road to groundwater sustainability.


By the way, Open ET does not just cover California. Their data set includes all 17 Western U.S. states, so you can see how the guys in Texas and New Mexico and South Dakota, Colorado and Kansas are doing as well. The presence of this technology is attracting national attention that may not be favorable to agriculture, such as the article featured below.