Lower Ark nets 800 acre-feet this season from a recalculation of pond seepage

Orr Manufacturing Vertical Impact Sprinkler circa 1928 via the Irrigation Museum
Orr Manufacturing Vertical Impact Sprinkler circa 1928 via the Irrigation Museum

From The Pueblo Chieftain (Chris Woodka):

A recalculation of the seepage rate of ponds used to feed irrigation sprinklers means farmers will have to repay less water than originally calculated this year under 2010 surface irrigation rules.

The savings amounts to about 800 acre-feet (260 million gallons) for Rule 10 plans operated by the Lower Arkansas Valley Water Conservancy District, a 40 percent savings.

The Lower Ark’s 2-year study still is not complete because of technical glitches. The Colorado Division of Water Resources accepted results for only some of the more than 20 ponds studied, and the state has asked for additional study in some areas.

But the results altered the basic formula for the Irrigation System Analysis Model. An interim seepage calculation method has been adopted as a result.

“(The division) does believe that the limited amount of pond study data from ponds where inlet and outlet meters were verified to be accurate are more comprehensive than what was used to derive the original seepage method in ISAM,” the state’s report noted.

Under the previous ISAM formula, the state estimated losses from the more than 145 farms covered by Lower Ark’s Rule 10 plans would create about 1,947 acre-feet of deficits. Under the interim method, the deficits total 1,137 acre-feet.

The 2010 rules were written to cover farms that have installed sprinklers or drip irrigation systems fed by ponds as well as other improvements in order to prevent increased consumptive use and potential litigation with Kansas over the Arkansas River Compact. Similar rules, written in 1996, already cover wells in the Arkansas Valley.

More Lower Arkansas Valley Water Conservancy District coverage here.

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