LAKE POWELL, HABITAT FOR WILDLIFE

Lake Powell and the Colorado River below Glen Canyon Dam are home to a vast and amazing variety of aquatic and avian wildlife including several species that hovered on the brink of extinction before they discovered the Lake.

Before construction of Glen Canyon Dam, silt-laden rivers - the Colorado, the Green, the San Juan and their tributaries - flowed through the canyon-country largely unchecked. Each year, when the spring thaw came to the mountains of the Colorado River Basin (April, May and June) the rivers would rampage wildly, scouring river bank and bottom alike in their journey to Lake Mead.

A few short weeks later, by early July, the run-off was over and the wild rivers became more sleepy, but still heavily silt laden.

Aquatic life in the river was limited. Because sunlight could not penetrate through the muddy water and the river bottom was continuously scoured by sand and silt, few if any aquatic plants could grow. Without aquatic plant life there are few aquatic insects.

And because of a lack of light penetration there were relatively few of the free floating microscopic plant and animal organisms that are known collectively as plankton.

Fish life in the river, as we know it today, was limited and similar in nature and abundance to that found further up the Colorado in Canyonlands National Park, in the Yampa River that meets the Green River in Dinosaur National Monument and through the Gray and Desolation Canyon country of the Green. In addition to widely scattered populations of Colorado squawfish, bonytail chub, humpback chub, and humpback sucker there were a few stunted cat-fish and not many other fishes in the free-flowing portion of the Colorado River System.

It's important to recognize that even before 1963, when Glen Canyon dam was completed and closed to begin impoundment of Lake Powell, Colorado squawfish, bonytail chub, humpback chub, and humpback sucker were on the verge of become endangered, threatened or rare.

True, the demise of these species is owed in large part to destruction of habitat as a result of dams and impoundments throughout their native range.

The ultimate "coup de grace" for several of these species occurred, however, at the hands of State and Federal Wildlife agencies - those who are responsible for the well being of our national wildlife heritage - as a result of a desire to create a premier sport fishery in Flaming Gorge Reservoir on the Green River in northern Utah/southern Wyoming.

Wildlife agencies at that time were exclusively engaged in the business of providing hunting and fishing related opportunities for citizens who financed these agencies through purchase of licenses and outdoor equipment.

Wildlife management, therefore, was geared to those species recognized as desirable for their sport and table qualities.

To assure optimum conditions for growth and survival of trout in Flaming Gorge, the entire Green River drainage from Pinedale and Big Piney, Wyoming, downstream to a point several miles below Flaming Gorge Dam was systematically chemically treated just prior to the closing of that Dam. The chemical compound used, generally referred to as "rotenone", is non-toxic to humans and livestock but acts on fish and other creatures who breath through gills by causing suffocation.

While the concentration of chemical in the waters of the Green was neutralized after it passed the Flaming Gorge Dam-site, the neutralization was not adequate to keep the residual chemical content from adversely affecting the native fish species mentioned above. The dramatic result was seen several days later. The surface of the Green River at Jensen, Utah, approximately 100 miles downstream was covered - clogged bank to bank as far up or downstream as the eye could see - with dead fish that had been native to the river system. This was the single event that, more than any other, spelled the real beginning of the end for the Colorado River drainage native fishery.

Today, the rampaging waters of the Lower Colorado through Glen canyon have been stilled, the silt load has settled. The water is clear, deep blue in color. The sunlight penetrates deep and because the water is rich in dissolved nutrients, there is abundant growth of plankton accompanied by ready growth in fish species which have been introduced into the lake by the Utah Division of Wildlife, the Arizona Game and Fish Department and the U.S. Fish and Wildlife Service.

Some native species, such as the squawfish, remain in the lake and seem to be perpetuating their numbers. Catfish have prospered and grown fat and sassy. But for the most part the aquatic animal population is now composed of introduced species like stripped bass, small-mouth and large-mouth bass, black crappie, sunfish, walleye, threadfin shad, crawdads, carp, an occasional trout and freshwater clams. As opposed to the river that was, Lake Powell is regarded as one of the best and most productive sport fisheries in the United States.

Much the same can be said about the section of Glen Canyon below the Dam and through the area known as Lees Ferry. This section has been managed by the Arizona Game and Fish Department for and has earned a deserved reputation as one of the top-rated "blue ribbon" trout fisheries in the world.

Fed by the clear, cool, nutrient enriched waters of Lake Powell, plankton and aquatic insects have prospered in this river segment allowing trout, which were introduced by the Arizona Game and Fish Department, to grow fast and large.

Bird life in general has prospered as a result of the lake. Our national symbol the Bald or American Eagle, currently listed as threatened by the U.S. Fish and Wildlife Service, is a regular fall and winter visitor to Lake Powell and the adjacent canyon country. These birds are attracted to Lake Powell because they are, primarily, fish eaters.

The Sierra Club cites an overwinter population of as many as 45 individuals in the Glen Canyon National Recreation Area. Annual January surveys conducted by the National Park Service indicate that 18 to 20 Bald Eagles winter here in an average year.

Bald Eagle populations appear to be recovering internationally and the birds may soon be removed from the Endangered Species list.

In addition to the Bald Eagle, there is a perennial nesting pair of Golden Eagle on Cathedral Rock, which is situated in lower Lake Powell, just up-lake from the Wahweap Marina.

The population of these birds fluctuates with the populations of their food base. They feed on rabbits and other small animals.

A good time for visitors to see eagles at Lake Powell is January-February when birds may be spotted roosting near the shoreline or circling in flight, "stacked-up", riding the air currents in such localities as the Great Bend area in the San Juan arm of the Lake.

There is little question that Lake Powell has been a major contributor to the recovery and well-being of the Peregrine Falcon, an animal that is currently listed as endangered. Peregrines began to show up at Lake Powell in the late 1970's.

Presence of the bird was first substantiated in the vicinity of Lone Rock, almost immediately adjacent one of the busiest visitor-use areas on the lake.

The birds were discovered as Lake Powell area residents when "down wash" from a TV News helicopter dislodged a falcon's nest from Lone Rock. The nest, complete with baby falcons, landed in the lake where a visitor rescued the fledglings and brought them to the Park Service Ranger Station at Wahweap.

In the past ten years or so, the population of Peregrine Falcons at Lake Powell has boomed. This growth in numbers is largely as a result of great numbers of water related insects which, in turn, attract healthy feeding populations of small birds such as doves, swallows and swifts, which are prey for the Peregrine.

Currently the National Park Service has surveyed only about half of the 1,932 square miles comprising Glen Canyon National Recreation Area for presence of Peregrine Falcons. They have found 75 occupied Peregrine territories -- an occupied territory contains a breeding pair plus young.

Based on Park Service data, it is estimated that that there may be well over 100 breeding pairs of these birds in the Lake Powell area. A total estimated population of 700 to 800 Peregrine Falcons associated with the lake is well within reason.

As a result of Lake Powell and it's positive influence on the Peregrine, it appears very possible that this bird will soon be de-listed.

National Park Surveys have also identified the presence of a very limited population of the endangered Spotted Owl within the Glen Canyon National Recreation Area.

The Spotted Owls are not generally associated with large water bodies. Their habitat here is in narrow side canyons where active streams exist. Here, in native stream-bank areas called riparian zones, they can more readily find preferred prey species such as packrats.

Lake Powell and the Colorado river for 15 or 20 miles downstream from Glen Canyon Dam are also a seasonal "home" to a wide variety of native shorebirds and waterfowl.

Populations of grebes, gulls, terns and various shore birds have all increased as a result of the lake and the ecosystem it has created. There is no good information available regarding nesting of these species. But there is no question that the lake is important to migrating waterfowl and shorebirds.

And because of the effects of the dam - clear water, high in nutrient content and thus producing great populations of plankton and aquatic insects - the area between the Glen Canyon Dam and Lee's Ferry has become heavily utilized by various duck species as well as by Canada geese.

Mallard ducks are now known to be nesting along the river near Lee's Ferry. And there is some indication that there may also have been nesting attempts by Gadwall ducks.

Waterfowl would not be here without the lake/dam. Clear, productive water is key to their presence. Pre-dam water, especially in spring, would have been muddy and food for these birds would have been scarce or non-existent.

Post-dam environmental changes to Glen Canyon Country have, as pointed out in the foregoing paragraphs, brought social, recreational benefits to visitors and have insured the survival and restoration of certain previously rare, threatened or endangered species of wildlife.

We should also address some of the less understood ecosystem changes that have occurred within the Glen Canyon Region as a result of the Lake.

Obviously, pre-dam Glen Canyon has been flooded.

The area that is now the lake bottom was a land of unbelievable and haunting beauty. It was termed "the place that no one knew" because access was extremely difficult and visitors here were few in number.

The overlying land forms associated with Glen Canyon country are largely sea depositions that were augmented by sediment eroded from the adjacent mountains. These sedimentary rock layers including marine limestone, shale and sandstone were laid down over hundreds of millions of years as sea water repeatedly covered and uncovered the area while nearby mountains and plateaus were geologically lifted and eroded.

Because much of the present surface of the region is sandstone, it's a good bet that many of the pre-dam formations embodied in old Glen Canyon were products of the forces of wind and water which carved labyrinthine canyons, arches and spires. Many of these pre-existing sandstone formations were doubtless destroyed - "dissolved" - as they became saturated and were covered by water.

The rising waters of Lake Powell were not only responsible for depositing silt carried by the river into these natural works of art, but during the early days of impoundment, the soil and vegetation that existed on many of the steep areas along the shoreline simply slid into the lake. Unfortunately, at this point in time, the Glen Canyon that was has been deeply covered not only by water but also be a thick layer of silt.

Despite the presence of the lake and the resultant siltation, the spectacular land forms and vegetation that characterized pre-impoundment Glen Canyon have not been lost however. They still exist in the dozens of side canyons adjacent Lake Powell. They are readily accessible to area visitors via boat.

Erosion and siltation is a continuing process. It is a natural part of any river system. High country erodes, washing silt to lower areas. When a river reaches the sea or any body of still water, the silt load drops. A delta is formed and, in time, increases in size. Eventually the sea, or water body, may be filled with silt. It may eventually turn to sedimentary rock. And through ensuing centuries, nature will whittle it away or build upon it. This is exactly the cycle of events that originally formed and shaped the Colorado Plateau and the North American continent.

Because Lake Powell is a water supply, flood control and energy producing reservoir, a germane question is, how quickly will siltation render the Lake unusable for the purpose it was created to serve. The Bureau of Reclamation, an agency of the United States Department of the Interior and the entity responsible for building Glen Canyon Dam, estimates the useful life of Lake Powell to be something on the order of another 500 years!

Birth of the lake brought other changes to the desert river ecosystem. Preexisting native stream-bank vegetation, probably composed largely of cottonwood, willow and similar species, was inundated as lake Powell formed.

Habitat for a wide variety of reptiles, various snakes and lizards, was destroyed. Many of these individuals moved to higher ground as the water encroached and reestablished themselves.

Riparian, stream side, vegetation has been replaced with Tamarisk, one of a group of plants that botanists refer to as phreatophytes or water loving plants. In the case of the tamarisk, it only grows where its roots are in a water saturated soil zone. As river or lake levels are drawn down, the roots grow to stay in that saturated water zone.

Evaporative loss from the Colorado River system is a matter of continuing environmental concern. Undoubtedly evaporation losses have increased as a result of a lake having replaced a river. The big question is, how much did they increase?

The Bureau of Reclamation recently completed a modeling study oriented toward identifying the net difference in loss of water from evaporation on a reservoir like Lake Powell vs. evaporative loss from a free flowing river like the Colorado. Considering the old river regime of spring run-off (high volumes of water coursing through rapids and accompanied by white water and lots of spray) and extreme summer-time heat captured and retained by rock formations in the canyon bottom , it was determined that evaporative loss from Lake Powell is about one third greater now than was the evaporative loss from the pre-dam river.

And the water "lost" from evaporation is not really lost at all. Moisture rich air is carried by wind currents from the vicinity of the lake to some other locality where it falls back to earth as rain. There it may nurture crop or forest lands.

Any discussion of evaporative loss is not really complete without further considering and weighing the evapotranspiration water loss from phreatophytic plants, like Tamarisk mentioned above, which grow thick and green along the banks of lakes and riverways throughout the west.

Since it's introduction into the United States about 100 years ago, Tamarisk has defied all attempts at control and has spread at a rapid rate. It is now present throughout the Colorado River drainage. Flooding, burning and plowing of the plants has had no impact. Indeed, burning and plowing or attempting to dig the plants has encouraged growth and proliferation.

Chemicals have shown some potential for control but their application is manpower intensive and not viewed as cost effective.

Tamarisk is, perhaps, the most effective and efficient natural evapotranspiration agent currently known. On a hot day, it is not unusual to watch water droplets form on the tips of the plant's branches, from which they are readily evaporated. And if water loss from evaporation is a major concern in the Colorado River basin, it is arguable that an immediate and aggressive research campaign oriented toward control of this plant needs to be undertaken.

If some so-called conservation organizations are successful in their desire to drain Lake Powell it is entirely possible that as the lake recedes to reveal a now-silted bottom and new shoreline, the same Tamarisk that lines the current lakeshore will almost certainly further encroach onto the new silt shoreline as the lake is lowered. Ultimately, what is now a shimmering body of turquoise blue water may be replaced by a thick, waving field of green Tamarisk bushes extending more than 150 miles up the river.

For more information contact. friends@lakepowell.org