Hypolimnetic Injection - 1994-95

The Students: Jeff Newberry (Senior) and Ed Cimbalik (Junior)

The Teacher: Clinton A. Kennedy

Awards: Awarded $6,500 from the Idaho Department of Environmental Quality for implementation of project - The Fish Saving Proposal - Hypolimnetic Injection


The anoxic conditions (lack of oxygen) prevalent in Cascade Reservoir have caused great concern among the towns people, the local businesses, and the Fish and Game. During the now annual algae blooms of anabana and microsystis, types of cyano-bacteria, the hypolimnion (bottom) of our reservoir has been going anoxic, causing problems for the people who love to fish this wonderful reservoir as well as for those whose livelihood depends directly or indirectly on Cascade Reservoir. Our reservoir has been ranked as one of the leading fishing lakes in Idaho for quite a few years. But with the hypolimnion reaching anoxic conditions this past summer, over 3,000 fish had to be transplanted to a nearby reservoir and many more died. If the fish continue to die and/or are removed then our tourist based economy will suffer greatly.

We set out to find a way to provide a sanctuary for the fish when the dissolved oxygen levels in the hypolimnion drop below 1.5 ppm and threaten their lives. After hours of intense research and conversations we decided upon the Fish Saving Proposal. The Fish Saving Proposal deals with the complex equations of fluid dynamics in order to inject cold oxygenated water into the hypolimnion of our reservoir. It involves feeding water from the tributaries on nearby West Mountain into a head, then piping it to the bottom of the lake. Once on the bottom of the reservoir the pipe will be branched off into smaller pipes, letting the water slowly dissipate into the hypolimnion. With the addition of this cold, oxygenated water the dissolved oxygen levels will rise, thus providing an oxygenated sanctuary for the fish to live in when the lake goes anoxic.

We recently received letters of commendation from the local Division of Environmental Quality and the Fish and Game. Both stated that our project was a very practical idea and would provide an oxygenated sanctuary that the fish can live in. A paper received from Janice Burke, a technologist with Dr. Ellie Prepas at the University of Alberta, stated the usefulness of injecting oxygen into the hypolimnion of lakes.

"Injecting oxygen in our study lake is very effective at reducing nutrient input to the water column from the sediments and at improving the water quality for fish. Oxygen is (obviously) not toxic and provides an immediate improvement in the oxygen conditions in the lake."


Over the years Cascade Reservoir has been known as one of the premier fishing spots in Idaho. Yet that honor is slipping out of our grasp, due to the bacterial algae known as microsystis and anabana. These two bacteria have been thriving in the ultra-eutrophic reservoir, causing anoxic conditions to occur. These anoxic conditions finally reached a climax last year when 3000 fish had to be transplanted to nearby Horsethief Reservoir while others simply died and dropped to the bottom. The Idaho Fish and Game documented that no usable trout habitat existed during these periods of extreme stratification in late summer. If these results continue to occur on a yearly basis, the city of Cascade will surely suffer, which is why we felt it was time to step in and do something for the reservoir and the town.

Cascade Reservoir is located in central Idaho, settled between the snowcapped peaks of West Mountain and the vast expanse of Long Valley, forming the core of the small community of Cascade, Idaho. Cascade sits at an elevation of approximately 4,000 feet and the mountains around it quickly rise to 9,000 feet. The reservoir covers 26,500 acres (approximately 17 miles long), while having an average depth of 26 feet. The main purpose of establishing the lake was agricultural. The water is used for irrigation all over central Idaho. Over time the reservoir created the tourist-based economy for the town on its shores and provided a home for a variety of life: trout, perch, bald eagles, deer, elk, and humans. With the lake's condition deteriorating year by year the lives of its animals and its citizens are being threatened.

The first step in tackling any of these problems is to identify what is going on inside the lake. Acquiring a basic understanding of limnology, the study of fresh water ecology, was a necessity. Our Advanced Biology class, directed by Mr. Kennedy, ran various tests on the reservoir using Hach and LaMotte kits, Colorimeter, fecal coliform, and the Spectrophotometer. These tests were intimidating and complex at first, but after time we were able to make sense out of the numbers. These numbers pointed toward the declining conditions that are prevalent in anoxic lakes. Low readings in tests such as dissolved oxygen, high readings in BOD, nitrate, and phosphate, and higher readings in tests such as fecal coliform assured us of the fact that we were not testing a healthy reservoir.

In order to get precise readings of the phosphate in our lake's water, we had to learn how the highly complicated spectrophotometer worked. We learned that organic molecules absorb radiant energy because of the nature of their chemical bonds. Proteins and nucleic acids absorb ultraviolet light in the wavelength interval 240 to 300 nanometers (nm), pigments and dyes absorb visible light 320 to 660 nm and other organic compounds absorb infrared energy. Color is determined by the ability of molecules to absorb light energy. If an object appears to be red then the object is absorbing all of the colors in the light spectrum except red, which is being reflected, and thus the object appears red to the eye. A spectrophotometer is designed to detect the amount of radiant energy absorbed by molecules in solution. Simply put, the spectrophotometer works by detecting the difference of intensity of light through a blank tube and the intensity of light through the sample. If the transmission of light through the solution is low there is a high concentration of the substance being tested. When the transmission is high then there is a low amount being tested. The first lab that we ran was a practice lab that dealt with methylene blue. Once we understood this lab we moved on to a phosphate lab. Before we could start running the tests on the spectrophotometer we had to set up serial dilutions of the phosphate. In order to make a serial dilution you first start with a known concentration. Then calculate the amount of diluted solution that you want. The next step is to calculate the ratio of original concentration to distilled water in order to get the desired dilution. Once the amount of distilled water is known, you head back to the lab and very accurately measure out both the volume of the original concentration and the distilled water. Once these two volumes are mixed together you now have your serial dilution. In our lab we started with an original concentration of .02 milligrams/milliliter (mg/ml.) and had to obtain serial dilutions of .0175, .015, .0125, .01, .0075, .005, .0025, and .0 mg/ml.

Once we had the above dilutions we went back to the spectrophotometer and ran our tests. With the numbers that the spectrophotometer spit back at us we were able to make a Beer's Law plot of transmission versus concentration and absorbance versus concentration. Once all of the points were marked on the graph we drew a linear regression line ( a line that best fits through or by all of the points) We could then find an unknown concentration by plotting either its percent transmitted or the absorbance on our Beer's Law Graph (graphs showing these results can be found in the appendix). For our unknown concentrations we used water out of the lake and were able to determine more accurately the levels of phosphate present in our reservoir. The results ranged from .05 ppm to .07 ppm ; these low numbers indicate that the algae have been using up most of the phosphate as a source for food and nutrients. Meaning that the algae can multiply freely, creating large numbers of algae each year. When this algae dies it settles to the bottom as detritus where it decomposes, using up the oxygen that the fish need to survive. The results that were obtained from the phosphate tests were not surprising at all. Since the problems with the algae first began, we realized that there had to be an excessive amount of nutrients available in the reservoir.

The dissolved oxygen tests measure how much oxygen is dissolved in water and is measured in parts per million (ppm). A quality lake that supports many different life forms has a range between 6.0 ppm and 10.0 ppm, at which point supersaturation is occurring. When the dissolved oxygen levels drop into the 3.0 ppm range to the 2.0 ppm range then the fish run into problems. These levels of dissolved oxygen start to become hazardous to the fish's health. Once the readings reach levels of 1.0 ppm to 0.0 ppm (anoxic conditions) then the fish will die. When we ran our dissolved oxygen tests in Advanced Biology class we measured dissolved oxygen reading that ranged from 7.6 ppm to 8.5 ppm. These results seem to indicate that there is no shortage of oxygen in the lake. This is especially true during the day when the algae are producing their food by means of photosynthesis, thus giving off oxygen and keeping the levels high. The problems occur at night and on cloudy days, when there is no sunlight available for photosynthesis. At these times the plants have to rely heavily upon cellular respiration in order to live. This throws off the balance between oxygen that is being released and the oxygen the plants are using. This causes the oxygen levels to drop extremely low, creating anoxic conditions in the epilimnion (the top layer of the lake). With the epilimnion unhabitable the fish move to the hypolimnion to live. Here they meet with the same anoxic conditions. This time the anoxic conditions are due to the decomposition of detritus (mainly the dead algae that have fallen to the bottom). During decomposition extreme amounts of oxygen are used by the bacteria, causing the hypolimnion to go anoxic.

These problems are compounded even further by the fact that thermostratification, the density layering of water, according to temperature, is occurring. Water of different temperatures have different density. When the water is layered it doesn't allow any mixing to occur, and when an area goes anoxic it stays that way until either spring or fall turnover. At these times the water in the lake reaches the temperature of 4 degrees Celsius, and now mixing is able to occur. The fish experience problems when the water in the hypolimnion goes anoxic due to the decomposition and thermostratification.

The next test we ran was pH. A healthy reservoir should only fluctuate .5 to 1 units around the neutral mark (7). If the pH reading fluctuates much more than this it can be very harmful to the organisms that occupy the reservoir. The pH level also has an effect on nutrient recycling and how much oxygen is dissolved in the water. The pH readings in our lake range from 6.75 to 7.0. It doesn't appear that the pH levels in our lake are contributing to the problems the fish are experiencing.

Temperature is another important test because it determines what life forms can live in the lake and the amount of oxygen that can be dissolved in the water. Trout, for instance, prefer a cooler temperature, 4 to 12 degrees Celsius. Water at these temperatures can dissolve up to 12 ppm of oxygen. If the temperature rises above 12 degrees Celsius water can only dissolve around 7-8 ppm. Since this project wasn't underway during the summer months, when the fish kills took place, we went to the local Division of Environmental Quality for help. There we wore told by Dewey Worth that "due to the shallow depth of the reservoir, summer water temperatures in both the epilimnion and the hypolimnion frequently exceed the state standard for water temperature necessary to support cold water species such as trout and salmon". These statements were also verified to us by Don Anderson of the Idaho Fish and Game. Mr. Anderson also stated that the main time these problems occur is during the stratification period. The first signs of trouble were observed by concerned citizens who noticed unusual numbers of fish trying to swim up the small tributaries. On the other side of the lake quite a few dead fish were found floating in the lake and occupying the beaches. As soon as the Fish and Game heard this information they tried to save as many of the fish as possible by transplanting them to Horsethief Reservoir, 15 miles away. It is obvious that fish do benefit from the colder, oxygenated water in the tributaries as demonstrated by the behavior of the stressed fish during last summers' fish kills. With the epilimnion too warm for fish to inhabit, due to the fact that it receives all of the suns light, and the hypolimnion slowly achieving anoxic conditions, the fish are being squeezed into a smaller habitat day by day (a graph describing this can be found in the appendix). Finally the livable area vanishes and the fish are left trying to make it up the shallow tributaries. With such a great distance of warm water to get through that the voyage that the fish make in order to find cold oxygenated water is almost suicidal. If our proposed project were implemented the fish would not have to take on this extremely dangerous voyage; instead the water that they are seeking would be right where they could use it.

Don Anderson stated:

"Injecting cool, oxygenated water from the tributaries into the hypolimnion should result in areas of hypolimnion that could sustain cold-water fish species. These areas would act as important sanctuaries during periods of extreme stress. The "saved" fish would then distribute throughout the reservoir as the water quality conditions improved."

Dewey Worth stated:

"Your proposal could provide additional habitat during critical summer months when stream flows have fallen and fish can no longer navigate the shallow waters to escape the reservoir."

We realized that the fish needed an oxygenated sanctuary that they could retreat to during the lake's rough months. By injecting cold oxygenated water into the hypolimnion of our reservoir we can save the lives of thousands of fish before anoxic conditions set in and wipe them out. If the fish are not saved soon, our beautiful town of Cascade could become just another ghost town. For years many of the towns in Idaho, including Cascade, have relied heavily upon the lumber-industry. With nearby lumber mills going out of business and Cascade supporting more people, we can not afford to lose the income that the lake provides. Everyone in our small town benefits from the tourists the fish bring in: grocery stores, local tackle shops, realtors, land developers, R.V. and recreational parks, construction workers, and many others. If our plan is implemented soon, which is highly possible, the town will not need to worry about having to survive on the lumber mill alone. Our project will provide the rapidly declining conditions present in the hypolimnion a constant supply of cold oxygenated water to combat the warm anoxic water that resides there. The creeks flowing into the lake provide a perfect resource for the cold oxygenated water the fish need to survive. Yet, as mentioned earlier, the fish could not access this water due to the shallow water levels in most of the creeks. Many of the fish died in attempting to swim up the streams and we resolved to help out by bringing the water to them. The addition of this commodity will also aid in the spring and fall turnovers. With thermostratification present, forms of immobile micro-organisms are stranded in the stratified layers of the lake. These micro-organisms depend on the oxygen present the same as the fish do because of their inability to stay on the epilimnion where they can survive by photosynthesis. When the oxygen levels drop the bacteria die off and become detritus, adding to the already abundant supply of nutrients present, on the bottom of the lake. This not only detracts from the trouts diminishing survival zone but, through decomposition, releases all the phosphate that the bacteria used for food back into the water column. There it will be allocated for bacterial reproduction again in the spring, after the turnover. The mountain creek water that we inject into the reservoir will allow the bacteria to remain living, so the excess phosphate will not be released back into the reservoir, allowing for a clean and oxygenated epilimnion, which will result in high numbers of fish.

Our project is a follow up on Tom Lance's February 8, 1994 Preliminary Feasibility Report, dealing with hypolimnetic injection. In his report Mr. Lance proposed to use 8" to 12" metal pipe in order to circulate the lake and ward off the algae blooms. Yet his project cost more than the people were willing to spend. So we focused on trying to save the fish. This resulted in an idea that seemed to be very practical. The hard part was that this was a relatively new idea; thus gathering information was very difficult. When we first introduced our project to most people, we were met with responses such as: 'I'm sorry, I have never heard of this. . ", with the exception of Mr. Lance himself who was regrettably unavailable due to the development of his Masters Thesis. So we were left with an idea, but no sources.

In order to learn more about hypolimnetic injection we decided to contact the local DEQ, Fish and Game, Soil Conservation, Forest Service, and various other professionals through a combination of telephone, mail, internet and E-Mail, and library searches. Our first step in learning more about hypolimnetic injection was to gain access to Tom Lance's Preliminary Feasibility Report. Even though this report was only a page long it provided us with enough basic knowledge to begin our own research. Now that we had a basic idea of hypolimnetic injection we contacted Dewey Worth of the DEQ, Don Anderson of the Fish and Game, and Jenny Fischer of the Forest Service. These three supplied valuable information pertaining to our project. Mr. Anderson supplied stats on the fish kills and the transplants to Horsethief reservoir. The stats included numbers on fish moved and the areas in which the fish experienced the most problems. Mrs. Fischer buried us with information about the names of the creeks, flow rates, volumes, water rights, and a fresh perspective on the location at which to inject the water into the lake (the pipe needs to extend far enough out so that it is never above the low water mark). Mr. Worth informed us about artificial circulation, aeration of stratified lakes and hypolimnetic injection. More recently he provided several transacts of the reservoir, where temperatures and dissolved oxygen readings were taken. With all of this information we attempted to model our Fish Saving Proposal with the computer program STELLA. Through further contact with teachers in Oregon, professors in Washington, and a computer scientist we determined that STELLA could not provide us with the information we needed: how far the water would diffuse throughout the lake, what size of pipes and holes would handle the pressure, the volume of water that would travel through the pipe in order to maintain a constant pressure, and the length of pipe that would work best. Without the help of the computer program, we had to use pencil and paper and the help of a couple of engineers. With their expertise and our persistence we were able to determine most of the answers to our questions. The answers were as follows: the pipe should be 3" to 4" in diameter, this could handle the pressure that the creeks exert and is also very economical, the pipe length should be long enough to get it out past the low water marks. We have come up with 5 different options for pipe structure that only test sites or computer programs can determine which is the best choice. We also came up with 3 proposed test sites. We will describe the options and test site below and put pictures of both in. the appendix.


  1. A - run a 3" - 4" main line along the bottom and then branch off the end of it with 2" - 3" hose, that loops around with a few holes This is in order to keep the pressure consistent.
    B - branch out of the main line with a "U" shaped pattern of 2"- 3" pipe, then drill holes in the back side. This would help to keep the pressure out of the holes constant.
  2. run a 3" - 4" main line out into the reservoir and then branch off with 1 " pipe that has holes drilled in it, in order to release the water.
  3. run a 3" - 4" main line along the bottom and put holes in it in order to release the water.
  4. run a 3" - 4" main line along the bottom and then branch off of it with a 2" - 3" line that has an open end, releasing the water.
  5. run a 3" - 4" main line along the bottom and leave the end open for the water to flow out.

Proposed Test Sites:

We have devised several options concerning the dispersement of water in the hypolimnion and we plan on testing on three separate tributaries along the 17 miles of lake:

The creeks that will supply the cold oxygenated water needed to save the fish are located on the west side of the lake and have had an average flow rate of 7.18 cubic feet per second (cfs) over the last three summers. Pressure will not be a big issue since the lake lies along side West Mountain which rises almost 5,000 feet straight up. This will provide adequate pressure in order to run our project. The creeks that we plan on using and flow rates during the summer months are: Deer Creek - 7.5cfs, Silver Creek - 2.3 cfs, Hazard Creek - 6.2, cfs Campbell Creek - 11.5 cfs, Van Wyck Creek - 13.8 cfs, and Gibson Creek - 2.7 cfs. We have also been considering using some of the creeks further north such as Poison Creek, which was one of the sites where intense fish kills took place. The fish will congregate around the areas where the water is diffusing out of the pipes.

We have looked into water rights and it seems that our plan will not violate any of them. This is a big plus since there are so many homes occupying the west side of Cascade Reservoir and it would not be to our best interest to upset these people. Since we have also realized that politics play a major role in deciding what gets done.

In order for our project to work, we will lay the pipe along the stream extracting enough water to serve our purpose. The pipe will run down the base of the mountain, building up head velocity. The head velocity is required to provide the pressure necessary to maintain the outward flow into the reservoir. We will be using PVC pipe that is approximately 3"-4" in diameter. In order to keep the head clean we plan on constructing a filter that will fit on the pipe, keeping out leaves and other rubbish. Once this is in place we will run the pipe down the creek bed, covering it up until it reaches the lake. This is another one of those moves that is done purely for political reasons (we need to have many people on our side, and if the landowners can't see the pipe they will be happy campers). We will attach the pipe to cement blocks and drop them to the bottom of the lake by boat. The length of pipe will be site specific. We will judge the length by the volume of water that is available and by the depth of the reservoir. If there is a great deal of water, we will be able to extend the pipe or its tributaries further into the water. If there is a small volume of water the pipe and its tributaries will be shorter. The pipe length will probably not exceed 200-300 yards, due to the fact that all we need to do is get the oxygenated water out into the lake where it is more available to the fish.

We have been looking into the price of this project and it seems relatively small. The PVC piping will cost: $0.50 per foot for the 1" pipe, $0.62 per foot for the 2" pipe, and $0.48 per foot for the 4" pipe. The cinder blocks, used for holding the pipes down, cost approximately $1.25 a piece. Dewey Worth of the DEQ has said that the funding of our project is a possibility and we might be able to get people to volunteer to help us. The majority of the work will be done by Mr. Kennedy's Advanced Biology classes. The labor includes laying all of the pipe and maintenance. To lay the pipe out we will have to attach weights to the pipe in order to keep it on the bottom of the lake and then use boats in order to get into the lake to place the pipe. With the options that we are proposing it will not be necessary to remove the pipes during the winter months when the lake freezes over, for two reasons. If there is still any water flowing through the creeks, which there is usually, then the pipes will not freeze and crack.If there happens to be no water flowing in the creeks then we simply need to pull the source end of the pipe out of the water.

In order to see exactly how effective our project is we will set up a schedule in which we monitor the levels of dissolved oxygen, as mentioned earlier. The water quality tests will most likely be run by future Advanced Biology classes, DEQ, Fish and Game, and ourselves. With the tests we will be able to determine that amount of dissolved oxygen that our project put into the reservoir by subtracting the readings we get after the project is in from the readings we got before we put the project in.

While working on our project we were able to gain a better understanding of how our lake works and what needs to be done in order to save the fish. We learned that because of the annual algae blooms of cyano-bacteria the lake is experiencing very low levels of dissolved oxygen, even anoxia, and high temperatures, both of which contributed to the major fish kills that took place last summer in Cascade Reservoir. It is obvious that in order to save the fish and our town, cold oxygenated water needs to be injected into the hypolimnion. With hypolimnetic injection the fish will be provided with an oxygenated sanctuary in which they can live when the conditions in the lake become to harsh for them thus saving both the fish and the wonderful town of Cascade, which rely so heavily upon a healthy reservoir.


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