Saving Cascade Reservoir: Removing Phosphorous Through The Use of Constructed Wetlands - 1992-93

The Students: Dorice Constans, Erin Kennedy, Tara Kennedy, Stephanie Schuette

The Teacher: Clinton A. Kennedy

Awards: 1993 Seiko Youth Challenge West Region Semi-Finalist and Finalist - Saving Cascade Reservoir - Removing Phosphorus Through the Use of Constructed Wetlands

Saving Cascade Reservoir:
Removing Phosphorous Through The Use of Constructed Wetlands

Cascade Reservoir is a seventeen mile long reservoir which lies in the mountains approximately seventy miles north of Boise, Idaho. Thousands of tourists travel to this lake each year for its recreational value, and the reservoir is the hub of the tiny community of Cascade, which lies on the southeast shore of the reservoir. But recently, Cascade Reservoir has been plagued by the onslaught of irrigation, leaking septic tanks, and cattle waste. The addition of extra phosphates has slowly been turning the lake toward ultra-eutrophication, and the surrounding wildlife and communities have suffered. It has become extremely apparent that the lake needs help.

Through the meetings of our Advanced Biology class every Monday and Wednesday night, we became increasingly interested in discovering a way to solve our lake's problems. We delved into books, hungrily tracing the very fundamentals of limnology and ecology and relating those aspects to the lake. Upon discovering the reservoir's eutrophication and stratification problems, we felt the most promising solution that could produce the best long term effects would be the construction of a wetland near a major source of nurient loading. The wetland will act as a sponge for the extra phosphates and nutrients, effectively pulling them from the reservoir to establish good water quality. Not only will the lake be cleaner and more appealing to swimmers, but a new wildlife community will spring up around the wetland. Deer, Sandhill cranes, fish, and even bald eagles will find the wetland a suitable habitat. The constructed wetland would impact the entire area.

We chose a small section of the lake at the mouth of the Goldfork river as a site for our wetland. The railroad grade at this area already provided a partial dam which would be needed to control the water level of the wetland. We immediately began to discuss the project with members of the Division of Enviornmental Quality, the Soil Conservation commission, the Fish and Game, and other local enviornmental groups. We were dissappointed to discover that the construction of our wetland could be too expensive to produce a reasonable cost/benefit ratio. As local engineers surveyed our location, they estimated that the cost of building a small dam and construction a wetland of large size would be over $100,000. Although we feel that both cost and size estimates have been over-estimated, the wetland faced other problems such as 80 acres of privately owned land in the area and a large spring run- off.

Besides these problems, we feel our wetland is a suitable solution to Cascade Reservoir's poor water quality. Our community has been greatly educated about the severity and complexity of enviornmental problems. If classes could be placed in charge of maintaining a wetland, the educational impacts could skyrocket. Already, this project has made a difference.

On a summer's day in the town of Cascade, the sun is bright and the vegetation is lush. In a car boomin' with the sounds of music and every window rolled down, four teenagers make their way to Cascade Reservoir. This lake is known for its excellent fishing, exciting skiing, and last but not least, it's nutrient overloading. As the teenagers jumped out of the car, they were nearly knocked out by the overpowering odor of dead fish that wafted to their noses from the lake. One might think that these four teens would immediately jump back in their car and race for home after smelling this aroma but, instead, they decided to brave the disgusting smell and take a dip in the water. They headed towards the shoreline and, after jumping over the thousands of dead, dried perch littering the beach, waded into the warm, slimy water. At this point, they concluded that swimming was a futile effort. It was time to go home.

As they cruised home, they decided something had to be done if they ever wanted to swim in the lake again. After moments of pondering, they knew that a solution to the lakes problem lay only within the boundaries of science. Within hours of summer vacation, the four teenagers were faced with a project that would be worth far more than an A in Advanced Biology. Thus began the teen's environmental crusade.

Cascade Reservoir, located in central Idaho, forms the core of the small community of Cascade, which lies on the south end of the lake. The reservoir is a 26,500 acre (17 miles long) impoundment of the North Fork of the Payette River. It has an average depth of 27 feet and serves as part of a system of many rivers and reservoirs to meet agricultural, flood control and hydro-power needs. A southern Idaho irrigation district contracts out approximately 200-300 thousand acre-feet of water from Cascade Reservoir every year. This water serves the irrigation needs of many southern Idaho communities such as Emmett and Eagle. As one of the top fisheries in the state, this beautiful reservoir is used extensively by boaters and fisherman, as well as water skiers and swimmers. Besides its many human benefits, the reservoir provides a habitat for several species of wildlife such as trout, perch, waterfowl, deer, and elk. Most of the uses of the reservoir are dependent upon its water quality.

We realized that the first step to solving the lake's diminishing water quality and appearance was to specifically identify all aspects contributing to the reservoir many problems. The initial step in identifying these problems was acquiring a basic knowledge of limnology. Limnology, the study of fresh water ecology, informed us of the inter-relationship between the biological, chemical, and physical features of the lake's water system. During a period of classroom study, we researched the ecology of lake systems and learned specific information about our local reservoir. We discovered that Cascade Lake has several physical characteristics that add to its problems. For example, the lake's large surface area and shallow depth make it easy for the temperature of the water column to be increased. Much of the reservoir's watershed is surrounded by irrigated pasture (about 9.2%) and forest land (about 77%). These two types of land contribute large amounts of phosphates to the watershed, and in turn, to the lake. To determine how poor our water really was, we began to conduct our own field research.

To start with, we needed to discover what was already being done by biologists and environmental action groups to combat the ailments of the lake. We attended a Cascade Reservoir Association meeting, which included discussion of the uncontrolled growth of aquatic plant populations that posed threats to recreation and water quality. The meeting signified the eminent concern for the stability of the reservoir by local residents and conservationists. Not only did this meeting provide us with valuable information concerning the specific problems of the lake, but it gave us several helpful contacts from which we later gained knowledgeable information. One of these contacts, the Idaho Division of Environmental Quality, led us on a field trip the following Saturday morning. We discussed wetlands and their affect on water, macroinvertebrates in determining water quality, and best management practices (BMP's). We also collected macroinvertebrates and observed both a natural and constructed wetland. This information provided us with a beginning and motivation to conduct our own tests on the reservoir.

Along with our Advanced Biology class, we obtained various water tests which could be used in fieldwork and would give some indication of the overall water quality of Cascade Reservoir. We began these tests by first obtaining water samples from several locations along the lake, as well as from different depths. We tested for the presence of water quality parameters such as carbon dioxide, dissolved oxygen, nitrates, and phosphates. We also identified pH levels, temperature, and turbidity. (Appendix I) By finding the different temperatures and dissolved oxygen levels at shallow and benthic depths, we could determine the amount of thermos/ratification (the division of the water column into non-mixing levels due to temperature and density) taking place in the reservoir. By reading pH levels, we could identify the acidity of the water column. Original phosphate reading on the Goldfork ranged from less than .1 ppm to .01 ppm. A reading as low as .02 ppm can indicate poor water quality, but as our readings were too low to be accurate we returned to the lab, to use a spectrophotometer to assist us in determining the concentration of phosphate found in the reservoir. After completing strenuous calculations for our water tests, we concluded that the overall water quality of Cascade Reservoir was of a medium to poor nature. Despite our extensive tests, we felt that more evidence was needed to accurately determine the actual water quality.

Along with chemical tests, we obtained biological samples to give a better indication of water quality. These biological specimens were collected during our excursions to the lake to conduct water tests. We gathered mud, rocks, sticks, and water that we felt contained the best representation of aquatic life in Cascade Reservoir. These samples were taken back to the lab and placed in a carefully monitored aquarium of lake water so that they would grow and develop as if they were in their natural habitat. After 15-18 days of growth, we observed organisms under light microscopes and dissecting scopes. (Appendix II, III) This information reinforced our hypothesis of relatively poor water quality.

After conducting our own field work, we again used classroom studies and books to guide our search for the specific cause of our lake's poor water. We found that two major problems act together to create a bad smell and disgusting appearance. First of all, Cascade Reservoir suffers from eutrophication. That is, the lake is "nutrient rich," as it has constantly been under the stress of the nutrient loading of nitrogen and phosphorous, two nutrients that plants and algae must have to grow. These extra nutrients provide energy for algae, which quickly use these to grow and develop. There will be a period of rapid algae growth until all of the nutrients have been used up. With no more "food" to eat, the algae die and float to the bottom as detritus. The bacteria on the bottom of the lake then decompose the detritus and use it for food. During this process the heterotrophic bacteria use up the oxygen on the bottom of the lake, making it anoxic. After the detritus has been decomposed, the original nitrates and phosphates are released back into the water column, and the cycle begins again. Also, Cascade Reservoir stratifies, or divides into non-mixing Layers of different temperatures and densities as the water column heats up. This is due to the large surface area and shallow depth of the lake. Together, the eutrophication and thermos/ratification limit the habitat for several species of aquatic life. For example, the trout can no longer live near the bottom of the lake due to lack of oxygen, and the top layers of the lake are too warm for the fish. Therefore, fish die, decay, and add to the complexity of the problem.

Because we did not want to rely on our information alone, we consulted Dennis Taggart, the proposer of a year round recreational resort on Cascade Reservoir. His colleague and chief engineer, Rick Orton, also accompanied him. During the presentation, a question was asked as to whether or not the new resort would further pollute the reservoir. Mr. Orton explained that any excess pollution caused by the resort would be removed by several systems, one of them being a number of constructed wetlands. These wetlands would be created to remove the nutrients from the water before it drained into the lake. Although these wetlands cannot be 100% effective, they would eliminate a large number of nutrients from contaminating the reservoir. It was this presentation that gave us the initial idea of constructing a wetland on the reservoir to aid in reducing nutrient loading. We felt that a constructed wetland on one of the major tributaries of the lake could effectively deplete nutrient loading, thus helping to solve the eutrophication of the lake and diminish the effect of stratification. After further field trips with our class we discovered what we felt would be a superior location for a constructed wetland; behind an abandoned railroad grade where the Gold Fork River flows into the reservoir. Not only was this area shallow enough to construct a wetland but the railroad grade already formed a partial dam stretching across the Gold Fork arm of the lake. (Appendix IV)

We began to contact several people whom we felt could provide us with any information pertaining to our project. Our first victim was Jim Messerli of the Bureau of Land Reclamation. During our meeting he produced a land ownership map of Cascade Reservoir, and our project hit a snag. The map accounted for approximately 80 acres of private land in the lake where the Gold Fork enters. Unless this land could be bought by the government or otherwise, we would be unable to restrict or maintain water levels over the private land. We later discovered that the possibility of negotiation by the landowners was favorable. With the prospect of buying the land now good, we began making contact with other sources that could provide valuable information concerning wetlands and their effectiveness in reducing nutrient loading.

Jim Messerli had a limited amount of information concerning a constructed wetland, so he advised us to contact Dewey Worth and Michael J. Ingham of the Division of Environment Quality (DEQ) to further our research. The results of one simple phone call to their office in Boise were gratifying. The two had been conducting studies on Cascade Reservoir's eutrophication problem for nearly a year, and were more than willing to bestow gobs of information upon us. David Blew of the Idaho Soil Conservation Commission sent us many lab reports that were studies on the effectiveness of constructed wetlands in removing phosphate, nitrogen, and other nutrients from an aquatic system. Also included in this package was a video dealing with the benefits and detriments of constructing a wetland as a means of solving water quality problems. On the whole, the information we received was extremely helpful to our project.

The potential of a reservoir to become eutrophic is greatly influenced by the land surrounding it, as it is usually the land and its uses that are the source of the nutrients that change a lake's condition. The loading of silt to the water column is signifigant, since this increases the area of shallow water and the amount of nutrient - rich sediments. This can cause algae and weed growth, which leads to eutrophication. As stated previously, these plants require both nitrates and phosphates to grow. The obvious solution to eliminate excess algae, then, is to remove their source of either phosphorus or nitrogen. Because many plants, specifically blue green algae, are able to extract nitrogen from not only the water, but from the air (which is 80% nitrogen), it would be virtually impossible to remove this source of food. Therefore, phosphorus is the limiting nutrient in regard to plant growth. As it can only be processed from the water (locked in organic matter and silts), it would be possible to remove this phosphorus and inhibit algae growth. But how could a wetland do all of this?

As the Gold Fork River runs into the reservoir, it carries many nutrient-rich sediments with it. If this heavy input of sediment rich water ran into a wetland, rather than directly into the lake, the silt would be allowed to settle to the bottom in the slow moving water. The phosphorus locked in this silt would also settle. Because a wetland maintains conditions suitable for growth of a dense stand of emergent aquatic, vascular plants (spaced 0.3 to 0.5 meters apart), the nutrient rich soil would be used as a contributor to plant life, eventually forming a new habitat for wildlife in the wetland area, while removing approximately 65%-85% of the total nutrients running into the reservoir at that location. These aquatic plants that soak up the nutrients could then be harvested to completely remove phosphorus from the wetland. If harvesting proves too expensive, there is still a high chance that the majority of the nutrients in the plants would be removed by the wildlife that uses them for shelter and food.

A riparian zone, a region near the shore of a lake that allows for the growth of dense plant life, would be effective in removing phosphorous from the lake. These zones act as a sort of sink for phosphorous because nutrient rich clays and soils are deposited in this zone. The plants then use the phosphorous, thus removing it from the water column. Yet, drawdown reservoirs, like Cascade Lake, eliminates the growth of the riparian zone. Because the water level fluctuates, a riparian zone may be able to start to grow, just in time to be flooded or left "high and dry" on the shore, where it would die. Therefore, a constructed wetland could replace the natural riparian areas that are unable to grow on Cascade Reservoir. In order to maintain a stable water level on the Gold Fork River entrance, we would have to build a small dam on a space in the railroad grad. With this dam, the water level inside the wetland could be manipulated and stabilized, even as the water level of the rest of the lake rises and falls.

The Gold Fork River contributes approximately 14% of the total phosphorous of Cascade Reservoir. An 80% efficient wetland placed where the Gold Fork enters the reservoir, therefore, could eliminate 11.2% of the total phosphorous. To achieve this efficiency our wetland must meet certain qualifications that distinguish a properly working wetland from an improperly working one. The water level must be maintained at an average of 18-26 inches year round to allow for maximum vascular plant development. The water would be held at this level by a dam on the railroad grade (Appendix V). Several types of plants serve as phosphate removes in a wetland system. Among the most effective of these vascular plants are cattails and bulrushes, which can thrive in any area of the wetland. Other plants include arrowheads, spike rushes, pickerel weeds, water lilies, and muskgrass. Elodea and nytella also contribute to remove phosphorus. When first planted, they should be spaced 0.3 to 0.5 meters apart, although they will later grow elsewhere naturally. Two to four years should be allowed for plant like to be firmly established, and it may be slightly longer before the wetland achieves it's highest possible phosphate out- take. This seemingly long growth period is relatively insignificant compared to the long- term effects the wetland will have concerning the improvement of water quality. There will be less nutrient loading, leading to a less eutrophic state. Algae growth will be significantly inhibited- leading to a healthier water system for a number of improved uses.

This wetland will not only produce chemical improvements for water, but will have vast effects on wildlife and recreation. With several floating nesting stations placed at various locations around the wetland, this marshy area will become the perfects habitat for many species of waterfowl including ducks, sandhill cranes, pelicans, loons, geese, and osprey. Already, bald eagles have chosen the Gold Fork site as a temporary home, and with the production of an increased food supply in the wetland, the eagles may find it a superior location to live. The wetland could even be make a national reserve to protect this endangered species. Not only birds will establish residence in, or near, our wetland. The wetland will provide an excellent place for fish to spawn, and the addition of a simple fish ladder on the dam will allow them to reach the wetland easily and quickly. The wetland will also provide a haven for frogs, salamanders, water snakes, mosquitos, dragonflies, and other insects, foxes, deer, elk, and other birds and animals. A new wildlife community will be formed around the wetland.

Finally, the wetland will improve the recreational value of the entire area surrounding recreational value of the entire area surrounding Cascade Reservoir. By improving the water quality of the reservoir, the lake will become more attractive to boaters, swimmers, water skiers and the like. Although the reservoir has become one of the state's best fisheries due to nutrient rich water, the recent nutrient overloading has caused fish kills. By removing some of the phosphates entering the lake, the fine line between being an excellent fishery and an ultra-eutrophic lake can be controlled, and fishing may improve. The introduction of a new wildlife community with deer, sandhill cranes, pelicans, and even endangered bald eagles will give tourists a unique glimpse of nature. Not only will this please the many tourists that visit the area, but it could possibly increase the amount of money earned through tourism annually. The wetland will most certainly increase the recreational value of the area as a whole.

Despite these beneficial influences of the wetland, our proposal still has many problems to overcome before in can be implemented. the problem of paramount importance concerns the spring run-off of melting ice and snow into the Cascade basin. During this season the water level of the reservoir and all of it tributaries rapidly rises. When the Goldfork River accumulates this extra water, it will proceed to run directly into our wetland which, at all costs, must be maintained at a depth of approximately two feet in order to ensure the survival of the riparian zone. This means that a significantly higher amount of water must be released into the lake during the high water season. With the excess water moving quickly through the wetland, much of the sediments, and phosphates, would not be given enough time to settle out the system. Instead, these particles would drain directly into the reservoir. This could reduce the effectiveness of our wetland from 80% to 10%. Even worse, this reduction in phosphorus out take would occur at a season when an extremely high amount of nutrients are contained within the water. However, our wetland would be quite large, so it is entirely possible that the water would be given enough circulation time to allow most suspended sediments to settle. Our wetland would still lose some of its efficiency, but not as much as it would under worse circumstances.

Other problems of our wetland are embedded in politics, rather than actual physical problems. As mentioned earlier, 80 acres of our proposed site is private land, and our wetlands cannot be constructed unless the land is bought. Even though negotiation with the landowners is probable, there is still the concern of where the money would come from. Speaking of money, the actual cost of building a small dam and maintaining our wetland was estimated (by engineers) to be over $100,000. However, our group was not asked to participate in the cost estimation process, and we know some of the participants who did discuss the costs were rather unimpressed with the project as a whole (due to politics, we assume), so we feel that the high figures could be a result of this poor outlook. In simpler terms, we do not assume that these figures are accurate. Too add to this confusion, these "cost and construction persons" stated that the entire, mile long stretch of the railroad grade needed to be encased in six inches of concrete to build a dam. We have serious doubts as to the truth of this, mainly because the dam that secures the reservoir itself is not completely encased in concrete. These people estimated that the width of our dam would be 50 ft.. Our group visited our wetland area many times, and each time decided that estimating the width of the railroad grade at 25 ft. was generous. Due to these inconsistencies, we used many of our own estimated figures, primarily based on our knowledge of the area and previous wetland studies, to determine a proper cost/benefit proportion. Of less importance, irrigators in southern Idaho have rights to the majority of the water in the reservoir. Keeping our wetland at a stabilized water level would likely create political problems, even though the amount of water kept in the area compared to that of the lake is fairly insignificant. To sum things up, many of our problems were basically political riff-raff. Often, our group had some difficulties keeping a positive outlook and dispostion in the midst of this political strife.

All of these problems seem to be trivial when compared to the educational benefits of our project. While we were conduction our own water quality tests at the Goldfork River, the crew form the television program, Incredible Idaho, journeyed to Cascade to film us for the program. This was the perfect opportunity for us to direct the public's attention to the reservoir's problems, and, we must admit, to ask for one glorious moment in the limelight (the program airs in one Northwest and one southern state). The public was able to see us using lab equipment and some of our school studies to acutally solve an enviornmental problem close to home. Our community's response was overwhelming. For the first time since our project commenced we felt as if we were actually accomplishing something.

After hearing more about our determination to help the reservoir, developer Dennis Taggart made us a generous offer. There were a few acres of extra land located on the property he had bought of build Valbois, his four season resort. This land was in a prime area for constructed wetlands. Because Taggart was so impressed with our Advanced Biology class, he agreed to donate the land to the class and assist us in constructing a few wetlands there. The class would be in charge of maintaining the wetlands, and studying them for future information pertaining to their effect on water. Future Biology classes would assume responsibility for the wetlands at the beginning of each school year. Instead of merely high school students, we could practically consider ourselves field scientists! the fact that Taggart laid the responsibility for the land in our hands, students hand, exemplified his trust in education (school) and our abilities. This trust was one response to our project that we had not expected, but was accepted with many thanks.

Also in response to our hard work, a few teachers confronted us with the idea of forming a Student Enviornmental group based on our reservoir. With such a group, we would be given the opportunity to propose ideas for environmental care to Idaho's legislature, and we could also lobby for a bit of extra cash to aid in our environmental projects. Our school applied for a grant to get our action group started, and it is currently in the works. Now the entire school would be given the chance to help the lake!

Our project does have it's drawbacks, but the project itself is not the entire issue in our situation. We managed to raise public interest in the lake and it's problems, and also helped to educate many people on the problems of Cascade Reservoir. Now, due to our motivation to cure the lake, many others have come forth with their own concerns and suggestions. We are greatly responsible for new studies being conducted, and for the sudden interest in the lake and science. If nothing else, our project forced people to open their minds and think.

Therefore, we feel that even if our proposed plan is unable to be carried out the entire project has been a complete success, from start to finish. The amount of knowledge we gained from this experience is indescribable. We hope that the completion of this project will help to influence others into working for the protection of the environment, and that we have participated in paving the way for the replenishing of the earth.

This web site brought to you by the Advanced Biology Class at Cascade High School

Back to the top of this page
Advanced Biology Home Page