by Denis Hall
The Colorado Riparian Association held its 12th Annual Conference in the eastern plains town of Brush, Colorado from October 6-8, 1999. The location was chosen to familiarize participants with Great Plains riparian systems important to wildlife and human industry, and was a departure from previous years when conferences were held in the mountains.
Exploration of plains riparian issues began with a lineup of excellent speakers who described natural systems and discussed concerns specific to the South Platte River and similar streams. Because management and restoration require knowledge of what such streams were like prior to settlement, most speakers directly or indirectly discussed whether the South Platte was previously narrow and wooded, or wide, sandy and shallow.
South Dakota State University’s Carter Johnson told how habitat along the South Platte has for millennia served as a transportation corridor, providing cover for hundreds of species of birds in migration. He described how, during stopovers, thousands of sandhill cranes fill the sky and endangered whooping cranes seek the shallow sandbars.
Johnson explained how cranes like open habitat, but in contrast, a profusion of neo-tropical songbirds nest in wooded, cottonwood and willow habitat. This “biodiversity trade-off” begs questions about how best to manage plains riparian areas: whether they should be managed for one or two listed species, or for a panoply of species to enhance overall biodiversity.
And manage we must. John Woodling of Colorado Division of Wildlife explained that populations of at least one-third of the native fish in Eastern Colorado are “in trouble.” He described Eastern Colorado fish populations as “highly interactive” with riparian systems and none too plentiful since streams are flashy, dry, and intermittent.
Changes in community structure and abundance of the 22 native fish species in the South Platte have forced listing as Threatened and Endangered by Colorado for more than seven of the species. Factors influencing the decline according to Woodling, are water quality and quantity, and flow periodicity.
“But the kicker is clean water,” stressed Woodling, “and that’s where a bunch like the Colorado Riparian Association can make a difference.” Woodling pointed out that because of agricultural industry and pervasive use of fertilizers, the South Platte contains greater concentrations of nitrogen than any river in the United States. He added that constructed wetlands and restoration of riparian vegetation can contribute to aquatic recovery.
Riparian vegetation along the South Platte is mostly native, reported CRA’s own Gwen Kittel. Kittel believes vegetation along the river was woodlands and wooded pockets prior to settlement. She described the floral community structure as a “patchy riparian mosaic” of mostly the same species we see today. The present plant community exists in response to a changed hydrology — fewer ice flows and less spring scouring, which has enhanced plant growth and created more woody habitat.
Changed hydrology and water developments are key to understanding what’s happening on the South Platte River. Plains rivers seldom escape consequences of upstream water diversion and depletion, yet they bear responsibility for supplying downstream users. Jon Altenhofen of Northern Colorado Water Conservancy District described how return-flow hydrology drives water development and management of the South Platte.
“Because year-around water supply and irrigation have allowed aquifer recharge,” said Altenhofen, “vegetation along the river has increased.” Altenhofen described differences between surface and subsurface water use, and how irrigators drilled wells to access water that had previously recharged the Ogalalla aquifer and South Platte River.
This usage eventually diminished return flows to the river and caused consternation from downstream folks dependent on those flows. Since 1970, augmentation plans have been required to replace water withdrawn by wells to satisfy senior, downstream water rights holders. Augmentation replaces the water extracted by irrigation wells.
Restoration of natural flow regimes was expanded upon by Colorado State University’s LeRoy Poff. Poff explained that ecological processes are affected by environmental variation, and that river flow is the “master variable.” If we change the environmental template of which natural flow regimes are part, he said, we can expect direct biological responses from changes in ecological processes.
“Altering the natural flow regime,” said Poff, “disadvantages native species by altering the ecological processes of which they are a part. We must approximate natural flows to maintain numerous species rather than optimizing flows for only one or two. A partial restoration of the natural flow regime can benefit ecological integrity and biodiversity.”
On the road
In another departure from precedent, 1999 Conferees jumped on a bus to tour area riparian, wetland and recharge augmentation sites. Instrumental in all this was 35-year Brush resident Steve Treadway. His was the first restoration project we visited.
Steve’s interest in CRA was piqued by Partners in Wildlife program leader Bill Noonan, who helped develop the Treadway Wildlife Area and introduced Steve to Alan Carpenter. “I grew up on a river farm in Illinois,” said Steve, “and thought maybe there was a way to merchandise nature and not cultivate crops. This parcel next to the river had what I was looking for. It takes less water to keep this as a wetland than it does to grow corn, which is what it was doing only two years ago.”
Steve recognized the need to market his ideas, to make the project pay for itself, and is currently looking into “eco-tourism” uses such as bird-watching, hunting and fishing. He sustained criticism from friends and neighbors for his progressive thinking. He said, “but they’re still all my friends, and now they are looking at it. I’m happy with what I’ve done and now I see lots of potential. There will be all kinds of people coming on board.” When Bill Noonan introduced him to Alan Carpenter, said Steve, “we used the Treadway Wildlife Area as a showcase. We walked the Area and I was interested in the plants. I didn’t know about the Riparian Association, but wanted to show the project to people who know what it is about. Alan and I spent the day together and decided to bring the conference here.”
Treadway Wildlife Area was only the first of four stops at eastern Colorado wetland and recharge sites. Recharge ponds on Smart Brothers’ Ranch and at Tamarack State Wildlife Area pass water along to downstream users in Nebraska. The program is part of a deal between Colorado, Wyoming and Nebraska to satisfy downstream needs.
Recharge basins at both sites have created substantial wildlife values, and, with differential rates of drying and filling, provide different habitats to different critters at different times. Tamarack covers 15 river miles and may recharge as much as 10,000 acre ft. of water. Water is pumped into shallow wetlands during winter where it seeps into the ground, then into the South Platte during summer to recharge the river when irrigation demand is greatest and when it is considered by some to be most beneficial to wildlife.
We also visited Brush Prairie Ponds, created and maintained by the City of Brush as augmentation sites. The 1500 acres host more than 30 ponds surrounded by switchgrass and wildlife, and are leased to the Colorado Division of Wildlife for bird habitat and hunting.
Arikaree River Preserve
The highlight of the trip for many was Thursday’s visit to The Nature Conservancy’s (TNC) Arikaree River Preserve. The heart of the Preserve is Fox Ranch, a cattle operation homesteaded in 1900 and continuing today under The Nature Conservancy auspices. “At the Arikaree River Preserve,” said TNC’s Chris Pague, “diversity of aquatic and semi-aquatic species is high. The Arikaree is an isolated system because the geology here recharges the river which contains almost all native fish.”
The Preserve includes three habitat types — short-grass prairie breaks, sandhills, and riparian — inhabited by mule and white-tailed deer, antelope, bobcats, coyotes, rodents, plains leopard frogs and a few remnant cricket frogs.
Pague said the Preserve is “the best known example of this type of a plains cottonwood-switchgrass riparian woodland in the world,” adding that prior to a 1935 flood of biblical proportions, the cottonwood forest didn’t exist. Other riparian species include big bluestem and yellow Indian-grass, both as much as six feet high, Canada wild rye, prairie sandreed, sand dropseed and peachleaf willow.
Although it rained consistently during The Nature Conservancy representatives’ presentation, clouds parted and the sun shone through as we walked the beautiful riparian area next to the Arikaree River. Those who had never seen Great Plains riparian systems marveled at the high grasses and diversity of species present.
Then we were served the best dinner ever by the finest cooks in Yuma County. And boy was it good.