From The Pueblo Chieftain (Chris Woodka):
To look at the numbers, you’d expect to see otters frolicking everywhere in the Arkansas River basin.
Then you realize that the nearly 10,000 storage vessels in Southeastern Colorado are spread over more than 28,000 square miles in mostly arid or semiarid areas. Then consider that many of the reservoirs are seldom full. Finally, the vast majority are pond-sized, not lakes.
Still, someone has to keep an eye on them all, because water stored in them rightfully belongs to someone else. In the past 10 years, there have been 79 orders issued by the state in relation to improper storage practices.
“The Arkansas River is a big basin, and there’s a lot of complexity in the basin,” Assistant Division Engineer Bill Tyner told the Lower Arkansas Valley Water Conservancy District last week. “We put our emphasis on the top 200 structures.”
Tyner then walked the board through the different types of reservoirs that are known to exist. Even that can be a problem to determine, because reservoirs are man-made, while natural features such as lakes, ponds or wetlands on a creek might show up in aerial photographs.
There are more than 1,500 decreed structures in the Arkansas Valley, although some may not be in use or are restricted.
Of those, only 20 hold more than 10,000 acrefeet (3.25 billion gallons), and another 169 hold more than 100 acre-feet.
The rest are there, legal to use, but subject to water rights administration. In other words, they cannot store water if a user with a senior appropriation right is calling for the water downstream.
The largest reservoirs are John Martin Reservoir, which was built for flood control and to settle interstate compact differences between Kansas and Colorado, and Lake Pueblo, which was built as part of the Fryingpan-Arkansas Project for water supply, flood control and recreation.
There are nearly 1,800 erosion control dams, which must be under 15 feet in height, store less than 10 acre-feet and can be drained in 36 hours. They have to be dry 80 percent of the time.
“There are a lot of these at the Pinon Canyon Maneuver Site to mitigate vehicle damage,” Tyner said.
As would be expected, erosion control dams are found in the hilly areas of the basin in the Upper Arkansas, El Paso County and the Spanish Peaks area.
There are more than 5,400 livestock tanks, which fall under a specific state statute that has the same criteria as erosion dams, but also sets a chronological priority within the same drainage.
“Livestock ponds have a seniority system, but it’s not as formal as a decreed right,” Tyner said.
Gravel pit ponds are a different category. There are about 750. The ponds intercept groundwater because of activities by humans, so must be augmented to replace evaporation losses. Those are most common on the Eastern Plains, where gravel mining is prevalent.
There are roughly 140 head stabilization ponds, which are limited to storing water up to 72 hours, by state policy, primarily to reduce sediment for sprinkler or drip irrigation.
Aside from the known reservoirs, there are unknown storage systems including post-wildland fire facilities, stormwater detention ponds and unregistered ponds used for erosion control, livestock or head stabilization.