If you have been involved with a water rights augmentation plan in Colorado, you may be wondering how transit loss works. Who pays for transit loss, who determines transit loss, and does transit loss ever change? We have all those answers for you in today’s blog.

Transit loss simply means how much water is lost in a stream or river system when water flows from one point to another. Transit losses can be caused by water being evaporated off the stream, used by plants on the bank of the stream or, most commonly, by leaking out of the stream into the aquifer adjacent to the stream. This transit loss value is generally expressed in terms of percent per mile of loss. As an example, if a river loses 1 percent per mile, over 10 miles the total transit loss will be 10%. Pretty simple stuff. But who pays for it?

Transit loss is most commonly assessed to augmentation plans. When the water right associated with an augmentation plan causes a depletion to the stream, the augmentation plan is responsible for replacing that depletion in time, place, and amount in the stream. Transit loss comes into play when the augmentation release is upstream of the depletion point. When there are transit losses, only a portion of the water added to the river upstream will make it to the depletion point. By releasing a calculated amount of extra water, we can be confident that the correct amount of water will be available to offset the downstream depletion when the released water reaches the depletion point.

The specific transit loss value assessed in streams and river in Colorado is the explicit purview of the State. The State and Division Engineers determine the transit losses which are to be assessed for any stream system carrying non-native water. These transit loss values can also change. It certainly stands to reason that transit loss can vary from the high-flow snow melt period to the hot and dry summer months. These transit loss values can vary from 0 percent, all the way to 100 percent if there is no water in a stream and released water is lost into the sandy streambed. However, if the values change, they are generally varied around the irrigation season and non-irrigation season and are set somewhere in the ballpark of 1 percent per mile.

While the State is solely responsible for assessing transit loss, water resources firms will often perform transit loss studies. Next time, we will look at how engineers can estimate transit losses in stream systems, so be sure you are subscribed to the LWS blog so you don’t miss out. And if you have a need for a water resources firm for an augmentation plan, well drilling, groundwater modeling, water rights cases, or more, please reach out to any of the people at LWS and we will be happy to put together a plan for your needs. We help with projects big and small. 

Bruce Lytle:        bruce@lytlewater.com

Chris Fehn:         chris@lytlewater.com

Anna Elgqvist:    anna@lytlewater.com  

Ben Bader:          ben@lytlewater.com