Chemical Characteristics of Emigration Creek

Kevin Whipple

Index:

     Introduction
     Dissolved Oxygen:
     Nitrates:
     pH:
     Phosphorous:
     Citations:

Introduction:

Emigration Creek is a system that has seen its share of human related disturbances.   As Salt Lake City has grown up into Emigration Canyon, there has been a lot of construction surrounding the creek including the building of roads, houses, and business establishments.   The creek has also been influenced by grazing during an earlier period. These factors all contribute to the chemical makeup of the creek.   Human populations give off waste products that leach directly into the creek from septic systems.     The water that flows into the creek travels through many storm drains. There are also natural compounds, or elements are important nutrients in the ecosystem of the creek.  Some of  these include dissolved oxygen, nitrates, and the pH level.

The following table is based on data collected by the Natural World class (Biol-104), by  Brandon Ornelo, at Westminster College of Salt Lake City Utah during the fall semester of  2000 using a commercial Hach limnology test kit.

Date

Dissolved oxygen

Nitrates

pH

10/1/00

10.10

1

7.4

10/11/00

10.05

0.8

7.6

10/21/00

10.00

0.6

7.9

10/31/00

10.20

1.7

7.3

11/10/00

10.00

1.6

7.7

11/20/00

10.10

1.5

7.5

Average

10.08

1.20

7.57

Dissolved Oxygen

The level of dissolved oxygen doesn't fluctuate that much. There is more oxygen dissolved in the creek in the fall, when these measurements were taken, than there is in the summer.  Cooler water dissolves more oxygen than warmer water. Dissolved oxygen is also high due to the rapid tumbling water descending over rocks as the creek passes over the Wasatch Fault that underlies Westminster campus below 1300 E.  Trout depend on the dissolved oxygen to breathe.  Some of the oxygen found in the stream comes from the filamentous green algae, specifically Cladophora. Since there is more of these in the fall , there is more dissolved oxygen in the water.  Since there is a good amount of oxygen dissolved in the creek it is a suitable habitat for trout

Nitrates

Nitrates (NO3-) are one of the most important inorganic compounds in any ecosystem.  Nitrogen is used by plants and animals  in nucleic acids and proteins.   Nitrates are very soluble in water and are transported to the creek from the watershed.    The concentration of nitrates is directly affected by the urbanization of the watershed.   Many people put fertilizers, which contain nitrogen compounds, on their lawns.   There are also a large number of people using septic tanks that leak human waste into the surrounding soil, which is then converted to nitrates by nitrifying bacteria.   The nitrates are washed from yards and streets into storm drains, then into the creek.

pH level

The pH levels in the creek are relatively constant, averaging at about 7.3. In looking at pH level from day to day, there is fluctuation between 6.5-8.0.   Many organisms are adapted to a specific pH range, and they cannot survive outside of that range.  There are diatoms in the creek that depend on a relatively stable pH range.   If the pH were too become overly acidic then these diatoms might not be able too survive which would affect the other animals that feed on the diatoms.  The pH level appears to be controlled by the large amount of limestone bedrock on the watershed.  In fact , a thick film of precipitated lime is secreted yearly by the biofilm which covers all rock surface of the stream bed.  Therefore the pH is probably stabilized by the amount of dissolved carbonate ions leached from the limestone rocks of the watershed and stream bed.

Phosphorous

Another very important  compound found in the creek is phosphorous (PO43-).   We don't have any quantitative data on the concentration of phosphorous in Emigration Creek, but this is an important nutrient for plants and algae.  This compound is also put into fertilizers and washed into the stream through the watershed and urban storm drains (Carpenter,pp.136).  

 There are approximately one-hundred-eight houses in the upper portion of the watershed in Emigration Canyon. Each one of these houses has a septic tank that invariably leaches phosphorous into the creek from drain fields. Fungi, and bacteria in the soil convert this human waste into phosphorous and nitrogen, which is then washed into the creek. 

At various times of year there are different levels of nutrients found in the creek. This affects the population growth of organisms found in the creek.   When the weather turns colder, leaves fall from the trees adding a lot of detritus to the creek which is rapidly decomposed by bacteria and fungi.  The resulting nutrient enrichment of nitrates and phosphates may be directly related to the population explosion of certain algal species in the creek in the fall, such as Cladophora (Smith pp.13-15) and diatoms.  These photosynthetic algae provide  food and an oxygen source for many other organisms in the creek. The roots of riparian cottonwood and willow trees, which anchor the banks of the stream may also play a role in absorbing excess nitrates and phosphates from the stream water (Peterjohn, et al. 1984).

Citations:

Carpenter,Stephen R. Professor of Limnology, Halverson. 1998. Ecosystem Ecology, Ecology, First Edition. Oxford University Press, New York.

Peterjohn, W.T. and Correll, D.L. 1984. Nutrient dynamics in an agricultural watershed: observations on the role of a riparian forest. Ecology, 65: 1466-1475. [cited on pp 99-100 of Ecology. Dodson et al. Oford University Press. 1998.]

Smith, Gilbert M. Professor of Botany, Stanford University. 1933. The Fresh-Water Algae of the United States, First Edition, Fourth Impression. Mcgraw-hill Book company,Inc., New York.

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