River health pondered as demands increase

By Cherry Sokoloski
North Forty News

The Cache la Poudre River isn't very big, but it is very busy, providing recreation, wildlife habitat and water for farms and cities.

Is it being over-worked? Is it still healthy? Those are questions being pondered as more and more demands are made on the Poudre River and its major attraction, water.

Water is a precious commodity in the West, and the rapid population growth along the Front Range has strained current resources. As a result, cities have made plans to expand reservoirs and build new ones. Current projects being studied include a new Glade Reservoir north of Ted's Place and the enlarging of Halligan and Seaman Reservoirs, both located on the North Fork of the Poudre.

In addition, the Pleasant Valley Pipeline, which takes Poudre water to Fort Collins and Greeley, went online in 2004.

All of these projects call for taking additional water out of the Poudre River for municipal use. In some cases, existing water rights are used --often converted from agricultural rights to municipal. In other cases, relatively new water rights have been obtained. The latter, called "junior rights," allow for taking river water when there is above-average runoff and senior rights have been satisfied.

The result for the river is a streamflow pattern that is much different from the one designed by Mother Nature. Because of projects new and old, streamflow is dictated not only by snowmelt, but also by water diversions and dams.

By the time the Poudre River empties into the South Platte, it's been put through the paces. The river is actually smaller by the time it reaches the east end of Fort Collins. Water quality drops as one goes further downstream and out on the plains, due to return flows from irrigation systems.

Mother Nature contributes to health problems for the river, too. Drought is a big factor, and in the last five years, the only peak flow on the Poudre that was average or better came in 2003, after a big snowstorm. The peak flow generally hits in mid-June, and this year's high point is again predicted to be lower than average.

The river is one thing that interests almost everyone, from farmers and fishermen to kayakers and kids. There are lots of river watchers out there, checking on the health effects of drought and current practices, as well as the positives and negatives of new water projects.

The North Forty News investigated some of the elements that contribute to--or detract from--the health of that public treasure, the Cache la Poudre River. Important issues in the health report include water quality, biological diversity and the physical structure of the river. These are affected by several factors, both man-made and natural. Factors include peak flows in the spring, storm runoff, fluctuations in the water level and the overall amount of water in the river.

Peak flows

Peak flows on the Poudre during May and June are the delight of rafting companies, and they also have big advantages for the river's ecosystem. According to Sara Rathburn, a river geomorphologist at Colorado State University, the peak flow on a river acts as a scouring agent, moving sediment out of the river bottom, moving contaminants that are attached to the sediment, and cleaning algae off the rocks.

If algae are not scoured off the rocks, they can form large nuisance growths. These "algae blooms" are not only an eyesore but harm aquatic animals by robbing the water of oxygen when the plants decompose. The big plants are also too big for aquatic bugs to eat. "It's all interrelated," Rathburn noted.

If the river can't transport sediment, it is deposited in pools, riffles and the spaces between rocks in the riverbed. This is a problem because clean gravel and cobblestone rocks are good habitat for aquatic insects, which feed the fish. Also, fish lay their eggs in the rocks, and sediment can smother them. "Fine sediments severely degrade habitat and lower diversity," said LeRoy Poff of CSU, a research ecologist who has studied streams in Colorado and other states.

Another effect of poor spring runoff is that trees can gradually encroach on the riverbank. This makes the channel smaller and increases the chance of flooding later on.

Rathburn, who studied the North Fork of the Poudre after a massive release of sediment from Halligan Reservoir in 1996, has seen firsthand the value of a good spring runoff. That sediment killed thousands of fish and filled up pools all along the North Fork. Spring of 1997, however, saw a big snowmelt that helped to flush out the sediment, so aquatic habitat recovered fairly quickly. "If it had happened during a drought," she said, "there would have been a longer-term effect."

For four of the past five years, drought has robbed the Poudre of a good, flushing spring runoff. In fact, the runoff in 2002 was the worst seen in a century.

Some of the new water storage projects will take water off the Poudre during peak flows, but the amounts drawn off will be relatively small.

Rapid fluctuations

Mother Nature causes gradual fluctuations in the river, of course, but diversions to ditches and reservoirs can cause dramatic fluctuations. These rapid changes are harmful to aquatic life, Poff explained, because the organisms are forced to move around to find habitat. When the river becomes very low or stops flowing altogether, a "bottleneck" or shrunken habitat occurs. Bottlenecks, Poff said, "have a very clear consequence of killing aquatic life. You can expand the habitat back after a bottleneck, but the species do not recover quickly."

Low water levels

Low water levels can be caused by normal changes in the seasons, by drought and by diversions to irrigation ditches and reservoirs. Low water levels affect the river's health in several ways, most notably by increasing the concentration of pollutants. "Dilution is the solution to pollution," as the common saying goes, and the less water in the river, the less dilution there is.

Low water levels provide less habitat for fish and other aquatic life, and concentrated pollutants can lead to algae blooms and reduced oxygen levels, meaning generally poorer water quality.

Looking to the future

"Our rivers are really not protected from ecological damage caused by streamflow alterations," Poff stated, adding that not enough attention is paid to subtle details such as sedimentation, fluctuation and base flows in the river. "I'd like the citizens of Fort Collins to have a discussion of what they'd like the river to look like," he said. "Otherwise, eventually you're going to get something that doesn't look a heck of a lot like a river."

In the next issue, the North Forty News will take a closer look at new and proposed water projects and how they could affect the health of the Poudre River, for good and bad. The complex issue of water quality in the river will also be addressed.