Zero Dependable Yield!

In a presentation given in June 2009, the Army Corps of Engineers noted the Chatfield Reallocation Project’s low reliability and high mitigation costs. At Chatfield, dependable yield from “natural” sources was 0.

A study covered in the presentation examined 82 reallocations at 29 lakes and found an average annual cost per acre-ft of $230, with a range of $50 to $980 per acre-ft. Using the same costing methods, the average annual cost for storage at Chatfiled would be $14,300 per acre-ft! (2009 prices)

One would think that these fundamental observations might prompt the Corps to conclude that Chatfield Reallocation is not a worthwhile project to pursue. Instead the Corps decided to issue a policy waiver to reduce the price it charges for storage. This change obviously makes the project appear more favorable than it really is.

A PDF version of slides used in the June 2009 is no longer available at its original address on the Corps website ( However, a copy is available here.

The only mention of zero dependable yield that we’ve found in the Draft Environmental Impact Statement is buried in Appendix BB:

Common measurements of dependable yield include: 50-year low flow; 2% chance; 98% reliability; 7-day-10-year low flow. At Chatfield, all of these measures of dependable yield are 0.