Change of Use in Colorado: Maximizing the Value of Irrigation Water Rights

Figure 1: A diversion structure which controls flow and measures the water going from the river and into a ditch.

Figure 1: A diversion structure which controls flow and measures the water going from the river and into a ditch.

Very often municipalities either own a senior irrigation water right or are considering the purchase of a senior irrigation water right and need to understand the potential yield of the right in a ‘change of use’ case in Water Court. A change of use case is when a water right is changed through the courts to another use such as an irrigation right being changed to municipal or commercial use, or to be used for augmentation. For information about the change of use case process have a look at our previous blog post on the subject. In these cases opposers may bring forward valid concerns with issues like sub-irrigation, a lack of good diversion records, or additional sources of water being used. If these concerns are borne out, it can cause a reduction in the amount of water that the municipality can change for a new use. There are also issues that can significantly hamper the changed volume of water, like inefficient irrigation methods, excessive ditch losses, or too short of a period of record with efficient irrigation practices. Here are some of the things to look out for before you buy an irrigation right for a change case to make sure you get the best bang for your buck.


Diversion and crop records are the foundation of good change case. Records for crops should note the type of crop grown, what field it was grown in, the irrigation method, all of the water sources for that field, and the way the different water sources (if there were multiple) were distributed. Without complete records, the next option is to make sure that the irrigator(s) of the fields for at least the last 20 years can be reached to request an affidavit of irrigation practices. Diversion records for the ditch or well in the change case should have complete monthly records for at least 20 years directly previous to initiation of the change case. If there are gaps in the period of record, there should be notes as to why. An engineer’s results are as strong as the information used to develop them, and good, complete records are the best defense against concerns from opposers.


Decrees are the legal instructions about how a water right can be used. Sometimes, irrigators do not follow these decree instructions. Using the diversion records, crop records, and aerial photographs of the area, make sure that all irrigation occurred within the decreed area. You can’t claim any water that was used outside of the decreed area in a change case. Also make sure that diversions did not exceed their decreed maximum flow rate. If a water right is only for 3 cubic feet per second (cfs), and the irrigator often diverted 4 cfs, you can only claim up to 3 cfs for your change case.


If the ditch shares being changed are water short, meaning there is not enough water for the whole crop, the efficiency of the system has an impact on the amount of water which can be claimed in the change case. If the ditch is water short and using an inefficient irrigation method, such as flood irrigating which is only 50-65 percent efficient, you may want to consider switching to a more efficient irrigation method, like center pivot irrigation which is 80 percent efficient, and farming for a number of years to build up the claimable water to its maximum before initiating a change case. This method also allows the municipality to bring in revenue from farming, while building good rapport with the farming community and insuring the maximum amount of water can be changed in the future. In short, more efficient irrigation methods allow the crops to use more of each gallon of water you apply to a field, meaning more consumptive use when the water is not as plentiful.


Most change of use cases will require at least 20 years of records. Anything less and you may have to fill the records with zeros to reach an appropriate length of time. These zeros will bring down the average annual water usage and the amount of water that can be changed in the case. If water was not used for some months or years in the middle of the period of record, this may be an issue. If a headgate for a ditch was washed out from a flood, or a pump for a well was broken, that can be excused and removed from the record for a reasonable period of time, but if water was intentionally not taken, or taken in a different structure, then that period of time will count with zero consumptive use and lower the amount of water that can be changed. Check the diversion records, and if there are any gaps, ask the irrigator why there are gaps. And when it comes to the number of years in the record, more is always better.

Figure 2: Main irrigation ditch in the San Gabriel Canyon, ca.1900

Figure 2: Main irrigation ditch in the San Gabriel Canyon, ca.1900


A change of use case is only changing the water from the specified well or ditch that was consumed by the crop, and since a crop has a maximum amount of water it can use, any other source of water that was used by the crop can lower the final amount of water able to be changed. All the water sources are competing in a zero sum game. These additional sources of water often come in two forms for which you need to be aware. The first is any outside irrigation water source not listed in the change case application. These sources can be alluvial wells, junior rights in the same ditch, or supplemental water run down the ditch, just to name a few. The impact of these additional sources all depends on the order in which the water is used. If these additional sources are only used when the primary right in the change case runs out of water, then there will be no reduction to the primary right in the change case because it was always used to the fullest extent. If multiple water sources were used indiscriminately, there could be a significant impact to the amount available from the primary right able to be exchanged. Be sure to ask the irrigator about every source of water used to raise the crops.

The second problem source of additional water is sub-irrigation. This is a much more problematic source of water because it is often a constant source of water competing with the primary right in this zero sum game. Sub-irrigation occurs when the water table below the crop is shallow enough that the crops roots can draw water directly from the water table, thereby reducing the amount of water needed from the irrigation source named in the change case. A high ground water table below the crop could cut your claimable water in a change case. Make sure to check aerial photos from non-irrigation months and look for green crops and grass, and if possible check the water levels of any wells on the property to make sure the water level is below the root zone for the crops planted. Also be aware that checking once may not be enough, as water level fluctuates throughout the year.

This may seem like a lot of work to have done before purchasing a water right, but considering that municipalities spend upwards of $30,000 or more for changed water per acre-foot, this is rather inexpensive due diligence. This kind of analysis done before purchasing a water right can help shine a light on the unknown outcome of a future change case and help avoid the costly mistakes that come from purchasing a water right, only to find out there isn’t much water that can be claimed in the change case.

Are you in need of a consultant to aid in your change of use case?