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A commitment to clarity: a comprehensive National Park Service study leads to critical discoveries and long-term monitoring at Oregon's Crater Lake.

Volcanic Mount Mazama used to be one of the tallest mountains in Oregon. But it blew its top 7,000 years ago during a series of violent eruptions that hurled debris in every direction and blanketed the Northwest with ash. The remains of the mountain collapsed inward to form a gigantic caldera six miles wide and 4,000 feet deep, encircled like a fortress with steep rock walls. Pools of rain and melting snow began to accumulate within the caldera, eventually transforming the great hole into a lake. Fed only by precipitation, with no inlets to bring water in or drain out, the lake stayed remarkably clear and blue.

In 1805 Lewis and Clark traveled across the breadth of northern Oregon collecting data for fur traders and map makers. But after reaching the Pacific Ocean, the explorers left Oregon without ever knowing that an extraordinary natural wonder - and the deepest lake in the United States-lay tucked away in the southern part of the state waiting to be discovered.

Ironically, it was the smell of gold and not the spirit of exploration that led the first white people up a long, sloping mountain that guarded over the lake. They were prospectors searching for the Lost Cabin Gold Mine. Although they never found gold at the summit, the color and clarity of the lake they saw in 1853 impressed them nonetheless, and one of the men wrote the name Deep Blue Lake in his notebook. The prospectors shared their discovery with other setders, but the lake's identity was soon overshadowed by tales of gold and Indians.

But not for long. During the next ten years, many more prospectors passed near the lake en route to and from the gold fields of eastern Oregon, and eventually word of its exact location surfaced in jacksonvine newspapers. This triggered interest in the lake and prompted a few expeditions of herculean proportions, such as one led by newspaper editor Jim Sutton in 1869. What began as a casual family outing turned into an aquatic adventure when Sutton and his friends hauled in lumber to build a boat, lowered the finished vessel into the lake, and paddled around. Sutton, who later wrote about his experience, named Crater Lake.

Five years later, Jacksonville photographer Peter Britt lugged his hefty photographic gear up to the rim of the crater and took the first photos of the lake. He circulated these among national magazines, and soon images of Crater Lake spread across the nation. These images reached as far as the plains of Kansas, where the description of a dazzling blue lake inside a crater setlled in the mind of schoolboy William Gladstone Steel, who would grow up to make the preservation of Crater Lake his lifelong ambition.

Once in Oregon, Steel met Captain Clarence Dutton, who shared his passion for Crater Lake and his desire to see it become a national park. To furnish scientific data to support the lake's importance, the two organized a U.S. Geological Survey party in 1886 in the Cleetwood - a 26-foot, half-ton boat that the crew shouldered in and lowered into the lake. Fitted with a piece of pipe on the end of a spool of piano wire, the Cleetwood sounded the lake at 168 different points to arrive at a reading of 1,996 feet - remarkably close to the precise sonar readings in 1959 that established the lake's deepest point of 1,932 feet. On the same expedition, a topographer surveyed the area for the first map of Crater Lake, and Steel named many of the prominent features, including Wizard Island, the symmetrical cinder cone rising 763 feet out of the water that resembles a medieval wizard's hat.

Steel's efforts succeeded in making Crater Lake the fifth national park in 1902. Though scientific studies of the 1890s explained some of Crater Lake's geological mysteries, the reasons for the lake's remarkable clarity - as well as its normal patterns and processes - went largely unstudied for decades. Then in the late 1960s, graduate students in aquatic biology at Oregon State University studied the lake's phytoplankton and zooplankton (microscopic plants and animals) and conducted tests for clarity. These were accomplished with a photometer, which measures the composition and depth of surface light penetration in the water, and with a Secchi disk. The latter is lowered into the water until no longer visible, at which point its depth is noted; as it is raised up, a second depth reading is taken, and an average of the two is figured. The Secchi disk yields a more subjective reading and is used for historical purposes. But since the lake had not been monitored regularly, the students had few references for comparing their findings.

Ten years later, Doug Larson, one of the former graduate students involved in the project, returned to Crater Lake to resume testing. When he compared his new readings with those taken ten years previously, Larson was dismayed. to find that lake clarity had decreased by 25 percent. Probing further, Larson found that the nutrient level in one particular spring along the caldera wall (later called Spring 42) was elevated. "My concern was that an active sewage drain field for visitor facilities was enriching Spring 42," says Larson, "because it was located just outside the caldera wall in very porous soil."

Crater Lake is oligotrophic, or nutrient poor, because it is deep, and little sediment or organic material flows in the lake - factors which also contribute to its unusual clarity. But with only sporadic readings taken between 1937 and 1969, it was embarrassingly evident that the available data were insufficient to determine whether the lake's clarity varied naturally or was declining. For this reason, Larson's findings, and his subsequent charges that the park was negligent in its handling of sewage, signaled a warning that a comprehensive study of this rare and extremely valuable lake was long overdue.

In 1982, Congress passed Public Law 97-250 authorizing an in-depth, ten-year study of the lake's components and processes - 80 years after enlisting Crater Lake into the ranks of our national treasures. The National Park Service (NPS) assembled a team of limnological and oceanographic experts, and the Ten-Year Limnological Study began that fall.

The team outlined five broad objectives it intended to accomplish during the ten-year study. Foremost was the need to study and understand the physical, chemical, and biological components of the lake. A second objective was to set up a limnological data base to compare present and future lake conditions. "We didn't know how this lake works," explains Gary Larson (no relation to Doug Larson), the project's principal investigator. "We couldn't determine what was or was not a normal condition because we lacked consistently collected data." Therefore, developing a long-term monitoring program to reveal the lake's patterns and fluctuations was the third objective. The fourth was to determine whether the lake had experienced recent changes - as Doug Larson's findings suggested; and if so, to assess whether they were related to human activity - as Doug Larson had charged. Identifying the causes and recommending procedures for mitigation was the project's fifth and final objective.

During the ten-year study, the team used an ecosystem approach to develop the data collection and monitoring programs. After determining the components that affect the lake ecosystem - for example, precipitation quantity and chemistry, lake-level fluctuations, thermal properties, solar radiation, intracaldera spring chemistry, lake clarity, color, water chemistry, particle flux, chlorophyll, phytoplankton and zooplankton, and fish - they used conceptual models to guide the research and analyses, assembling a data base for each component.

"We learned right away that Crater Lake is an extremely complex and dynamic system," explains Gary Larson, "with considerable seasonal and annual variability. Its volume responds quickly to changes in precipitation because the basin has no surface outlet and water leaves only through seepage and evaporation." Learning how Crater Lake recycles its nutrients was critical to understanding its overall chemistry, so oceanographers Jack Dymond and Robert Collier - both on the faculty at Oregon State University - developed a model of the lake's nutrient budget. They determined that the level of dissolved salts in the lake was higher than could be explained by normal lake processes and suggested that another source of salts - hydrothermal, most likely - existed within the lake system. This news surprised no one. The existence of thermal features on the lake floor was first suggested in 1968, supported further in the 1980s and confirmed in the early 1990s by geochemical testing and models.

Then part way through the ten-year study, a fortunate event enabled project scientists to explore the effects of hydrothermal inputs on the lake chemistry and sample its deep water biology to a far greater extent than originally planned. In 1988, Congress passed Public Law 100-443, ordering a report on the significant thermal features of national parks, legislation that NPCA supported and played a major role in getting passed. At the same time, a geothermal energy company just happened to be drilling exploratory wells adjacent to the park boundary. "Although the objectives of the park's hydrothermal study were unrelated to the exploratory drilling," explains Mark Buktenica, an aquatic biologist at Crater Lake National Park, "the timing provided the political impetus to fund the research." Upon hearing of the park's hydrothermal study, the National Geographic Society and the U.S. Geological Survey spruced up the original National Park Service funding for the hydrothermal study - thus creating a rare opportunity for Buktenica and other scientists to explore the depths of Crater Lake in Deep Rover, a state-of-the-art submersible engineered for a single scientist-pilot.

Deep Rover is a scientist's dream. Compact and easily manipulated, it is capable of supporting a six-hour dive to 1,000 meters (3,000 feet). The main compartment is a clear acrylic bubble hinged at the top like a giant clam shell to let the pilot enter and exit, and affording 360-degree visibility with lights.

To furnish the study, more than 30,000 pounds of scientific equipment - including the 7,000-pound submersible - landed on Wizard Island by helicopter. At the insistence of the National Park Service, this was to be a no-impact study on the lake and Wizard Island, where the operation was staged. As a result, afl waste products were removed daily from the site.

Though scientists explored only 1 to 2 percent of the lake floor, Deep Rover opened a brief and rare window to the geological and biological secrets at the bottom of the lake. "We were able to see and document some extraordinary features on the lake floor," says Crater Lake's Buktenica, "such as the blue saline pools and brilliant bacteria mats associated with hydrothermal venting and extensive fields of moss, which up until then had gone unrecorded."

Cruising the bottom of the lake in Deep Rover provided scientists with valuable information on the geothermal and biological components of the lake and the pre-eruptive history of Mount Mazama, but unfortunately, it shed no new light on Spring 42. The charge that its elevated nitrate level was the result of the sewer system that served the park's visitor complex continued to haunt the ten-year study, and in 1988 plans to remove the drain field on the rim were initiated.

While an estimated 90 percent of the new nitrogen entering the lake each year comes from the atmosphere, the remaining 10 percent comes from other sources associated with the caldera, including springs flowing from the wall of the caldera into the lake. Nitrogen is an important nutrient for the growth of algae and a component that affects lake clarity. Even though Spring 42 contributes less than 1 percent of the annual input of new nitrate into the lake, the park continued with plans to remove the drain field on the rim.

"It's a small amount relative to the total amount of nitrate in the lake," explains Stan Loeb, a limnologist at the University of Kansas and chair of the peer review committee for the ten-year study, "but the point is to avoid adding more nitrate to the lake.' Though water chemistry analyses did not confirm that the drain field on the rim was indeed the source of Spring 42's higher nitrate level, the drain field was removed it," adds Loeb, "especially since the spring's nitrate levels were the same before and after its removal.'

Even with the drain field removed, the mystery of Spring 42 lingers. Located in one of the wettest parts of the caldera, it empties from an orifice in the caldera wall and does not have far to travel to reach the lake. "It stays very cold, even in summer," reveals Gary Larson, "and it may be a different kind of system than other springs in the caldera." While soils saturated with nitrate from the drain field could be one of the reasons the spring still shows the same nitrate concentrations as before removal, Larson is not sure . "If the numbers drop in a few years, then perhaps the drain field was responsible, but we're not ruling out the possibility that nitrates in Spring 42 may well be a natural phenomenon."

In any case, sewage is now piped into a drain field off the rim and well away from any of the caldera springs. The improve sewage system was tagged on to the $15-million rehabilitation and reconstruction of Crater Lake Lodge, which reopened in May. Although the lodge opened in 1915, it collapsed twice during the park's typically massive snowfalls and was never completed; the original plans - if there were any - were never found. The new exterior remains largely unchanged from the original, but the interior has been modernized to create the mood of a true mountain lodge.

No doubt the renewal of full accommodations at Crater Lake will increase visitation, forcing the park to tackle perhaps its greatest challenge yet: how to provide an enjoyable and educational experience for more, while affecting the lake less. Now that sewage is no longer a possible threat, other human-related factors such as global warming, air pollution, on-site boat use, and non-native fish (introduced between 1888 and 1941) could be the next to encroach on Crater Lake's pristine condition.

As might be expected, the Ten-Year Limnological Study generated many questions that simply could not be evaluated in a ten-year cycle. But at least it convinced the Department of Interior to apply a segment of Crater Lake National Park's annual operating budget toward long-term limnological monitoring. Gary Larson and his assistants monitor the lake's clarity monthly, between July and October, from a boat housed on Wizard island. In August of 1994, they recorded the highest clarity readings to date.

"While the ten-year study revealed many components that influence the lake's clarity," says Larson, "it's going to take at least two to three decades of data to fully understand how this lake works. We have to sort out the natural changes in the system from any that may be caused by human impact," he adds, "and only long-term monitoring can provide answers about the lake's trends and status."
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Copyright 1995 Gale, Cengage Learning. All rights reserved.

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Author:Weingrod, Carmi
Publication:National Parks
Date:Jul 1, 1995
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