EFFECTS OF EUTROPHIC STORMWATER PONDS ON CLEAR CREEK
WATER QUALITY IN WHEAT RIDGE, COLORADO
Lisa Eagle, Ethan Newman, Clif Burt, Andrew Keiswetter, & Isaiah Sleeger
12/7/2012
For:
ENV4970
Dr. Janke
Metropolitan State University of Denver
Fall 2012
EFFECTS OF EUTROPHIC STORMWATER PONDS ON CLEAR CREEK
WATER QUALITY IN WHEAT RIDGE, COLORADO
Lisa Eagle, Ethan Newman, Clif Burt, Andrew Keiswetter, & Isaiah Sleeger
Abstract
Polluted stormwater runoff is one of the leading causes of decreased water quality
to water bodies across the country. Nutrients such as nitrogen and phosphorus, normally found
in stormwater runoff, can lead to degraded conditions within water bodies affected. Retention, or
wet ponds, are commonly used in developed areas for a number of purposes including
detainment and improvement of water quality through filtering of pollutants. These ponds hold
stormwater indefinitely, releasing excess as needed into nearby receiving water bodies. Prospect
Park in Wheat Ridge, Colorado contains four such ponds, two of which, Prospect Lake and Bass
Lake, discharge directly into Clear Creek, a major watershed. Prospect Lake was observed to be
experiencing eutrophic conditions, while Bass Lake was not. Data was collected upstream and
downstream of the discharge points to determine if the ponds were creating water quality issues,
and for comparison of the two water bodies. The type of data collected included levels of nitrates
and phosphates, and aquatic invertebrates as they are an indicator of water quality. The data
obtained was used in forming a conclusion of whether the wet ponds in Prospect Park are
designed and maintained properly to ensure water quality of Clear Creek.
Key words: Stormwater, Eutrophication, Nutrient Pollution, Retention ponds, Wet ponds, Water
Quality, Aquatic Invertebrates
Introduction
Eutrophication is a very slow process involving the natural aging of lakes and ponds that
begins with the addition of nutrients into the system which promote the growth of phytoplankton
such as algae (The Open University, 2012). However, human activity such as agriculture, use of
fertilizers, and changes in land surrounding aquatic environments speed up the growth of
phytoplankton (USGS, 2011). Rivers, streams, and stormwater discharge are mostly responsible
for the loading of nutrients to aquatic environments through point and non point sources. Point
source pollution originates mainly from industrial sources and wastewater treatment plants.
1
Nonpoint source pollution mainly stems from urban and rural land uses, varying from lawns, golf
courses, surface runoff, agricultural fields, and atmospheric deposition. (Mueller and Spahr,
2006).
Nitrogen and phosphorus are two of the most important nutrients involved in the process
of eutrophication. In freshwater environments such as lakes and ponds, phosphorus is most often
the nutrient in the lowest concentration and thus usually limits the growth of phytoplankton
(Schindler, 1977). In coastal marine environments nitrogen, being the nutrient in lowest
concentration, normally limits the growth of phytoplankton (Howarth & Marino 2006).
Although, recent studies have indicated this to be a generalization making it difficult to take
steps in improving eutrophic environments because existing models may not provide correct
insight into the true role of these nutrients in differing ecosystems (Elser 2007). Nitrogen is
commonly found in aquatic environments as nitrate (NO3-) or ammonia (NH4+ or NH3). Human
activity affecting the concentration of nitrogen in aquatic environments includes fertilizer runoff,
animal waste, wastewater and septic system effluent, fossil fuel, and industrial discharge
(Bernhard, 2012). Phosphorus is commonly found in aquatic environments as phosphate (PO4-3)
(Lee, 1978). Human factors affecting the concentration of phosphorus in aquatic environments
include detergents, fertilizer runoff, animal waste, wastewater and septic system effluent,
development/paved surfaces, industrial discharge, phosphate mining, drinking water treatment,
forest fires, and synthetic material (Khan & Ansari, 2005).
Excess nutrients promote phytoplankton such as cyanobacteria and dinoflagellates which
are responsible for surface scum, oxygen depletion, and resulting fish kills (Smith, Tilman, &
2
Nekola, 1999). Low dissolved oxygen concentrations can result from the decomposition of
phytoplankton. As bacteria decompose phytoplankton, they take up dissolved oxygen which is
essential to many organisms living in aquatic environments. Therefore a decrease in dissolved
oxygen concentrations could affect the ecosystem as a whole (Rushforth, 2009). Also, changes in
the abundance and species composition of phytoplankton can change the quality of food
available to higher trophic level organisms (Zimmerman). Additionally, blooms of
phytoplankton can reduce the amount of light available to organisms and plants beneath the
surface layer through turbidity and light attenuation which is the decrease in light intensity as a
result of absorption of energy and of scattering due to particles in the water. Submerged Aquatic
Vegetation (SAV) can be very sensitive to changes in water clarity, and if affected by severe
eutrophic conditions, may cause a change in species composition (SERC, 2005).
Many state and federal agencies monitor surface and groundwater quality with the goal of
preventing severe eutrophication. Dissolved oxygen, pH (Janke, 2012), nutrients (nitrates and
phosphorus), and chlorophyll are just a few of the water quality parameters that are often
monitored (Kenney, Reckhow, & Arhonditsis, 2007). Because nutrients can come from many
sources, wide-ranging strategies through watershed management are required to control
eutrophication. A range of watershed programs have generated success, but they cannot keep up
due to the increasing number of lakes and rivers experiencing these conditions (Stednick &
Hall).
Stormwater is a broad term that refers to all water running off of the land’s surface after a
rainfall or snowmelt event. Naturally it is a small part of the annual water balance, but as
3
development increases, impervious surfaces such as parking lots, roads, shopping centers, and
residential areas contribute to less water soaking into the ground and increased water runoff
along with pollutants that are carried from these surfaces (EPA, 2009). Starting in the late 1990s,
the Environmental Protection Agency (EPA) began to enforce requirements for stormwater
runoff containment and treatment through the Clean Water Act (CWA) where those responsible
are to follow set construction, maintenance, and design conditions (EPA, 2009). Stormwater
ponds (retention or wet ponds) and wetlands should be designed and constructed to contain and
filter pollutants that flush off of the landscape. Without proper maintenance, nutrients such as
nitrogen and phosphorus collect creating water quality issues such as algae blooms, low
dissolved oxygen, high pH, impacts to aquatic habitat, and unpleasant odors. When these excess
nutrients are discharged to a receiving water body, water quality issues can be created (EPA,
2009 February).
Prospect Park in Wheat Ridge, Colorado contains four stormwater retention (wet) ponds.
Tabor Lake and West Lake discharge directly into Prospect Lake and Bass Lake respectively,
and Prospect Lake and Bass Lake discharge directly into Clear Creek. Prospect Lake was
observed to be discharging large amounts of algae into Clear Creek in the fall of 2012. As stated,
Bass Lake also discharges directly into Clear Creek, but appears to contain minimal amounts of
algae. Clear Creek, which originates at the Continental Divide in the Rocky Mountains of
Colorado, and extends to the South Platte River, is a body of water that provides municipal water
for many communities along its course. All of these wet ponds appear to be sufficient for their
holding capacities, but a question was raised as to whether they are being monitored, or had been
designed sufficiently for filtering capabilities, per EPA and Clear Creek Watershed Foundation
4
standards (Clear Creek Watershed Foundation, 2007). Also, what are the effects of the observed
discharge to Clear Creek water quality, specifically nutrient levels associated with
eutrophication? These questions and others may be answered through upstream and downstream
sampling of water quality parameters such as nitrates, phosphates, pH, and aquatic invertebrates
within Clear Creek at either side of the points of discharge. A comparison between the two
ponds may also help to draw conclusions about how Prospect Lake compares to Bass Lake, and
what design implementations can be made to improve the efficiency of their filtering capabilities.
Literature Review
Storm water retention/wet ponds
Storm water retention ponds, or wet ponds, are designed and constructed to contain and
filter pollutants that flush off the landscape. Without proper maintenance, common nutrients such
as nitrogen and phosphorus found in storm-water can cause problems such as eutrophication.
Humans are often directly responsible as the sources of excess nutrients present in storm-water
runoff. Anthropogenic sources such as wastewater treatment, agriculture, and urbanization all
contribute to the problem. These and other natural sources such as erosion and precipitation
contribute nutrients that are all eventually washed into the watershed system and end up in lakes,
reservoirs, and ponds(Gelder et al 2003). These bodies of water can become the sources of water
quality issues and then become problems for other connected downstream waters.
Humans can also help the watershed ecosystem in a number of ways through remediation
practices. Some examples of this include creating phosphorus sinks, aeration, dredging,
introduction of aquatic plants, reduction of waterfowl, and diverting storm water inflows
elsewhere. Most of these examples have both benefits and drawbacks, and are usually expensive
5
to do. Phosphorous sinks are used when eutrophication is caused by internal loading of the body
of water. Essentially, ferric oxide is dumped into the water and it chemically binds to the
phosphorous to create reduced version of phosphorus that doesn’t contribute to the eutrophic
conditions anymore. Dredging is employed sometimes in problem areas where internal loading
issues have become critical and waters become unable to support most life. It requires
excavating the top layer of sediment from the bottom of the lake and it can be very expensive.
Aeration is used to oxygenate the water and in turn, reduce the anoxic conditions that contribute
to eutrophication problems. Introducing more aquatic fauna and plants is somewhat effective in
certain cases. They use and absorb the nutrients in the water to sustain their own life and in turn
filter out some of the excess nutrients that become problematic over time. Reductions in
waterfowl, particularly loafing species such as Canadian Geese and Mallards can reduce nutrient
loading as well. It both reduces the amount of grazing on the important aquatic plants, and
reduces the amount of their excrement waste that ends up in the water and causes problems (EPA
2009). In all cases, it is beneficial to catch the problem before it becomes out of control and use
the simple and more inexpensive remediation efforts to correct the problem quickly.
Aquatic Invertebrates
An interesting statement was made about sampling methods entailing that it is best to keep
them quick. Over sampling that produces a large mass of material, becomes a waste of time to
sift through, and does not help with the overall results. A technique used when there was an
extensive amount sampled, was to put the container in the hot sun and cover one side. In the
exposed side they placed the algae/moss, and on the other side, they kept it open and placed a
shade cover over that half. It was found that in the hot sun the invertebrates quickly removed
6
themselves from the algae/moss and swam to the cooler, darker covered side, making them easy
to separate and quantify (R Chadd 2010).
Collecting in mid depths such as less than a meter is the ideal method. Collecting at depths
great than a meter pose issues for collection and does not provide any improved results.
Collecting at the end of summer and into mid fall is said to be the best for results both in species
abundance and in maximum effects of stressors. At this time of year aquatic invertebrates are
found both in adult and larval stages and have gone through their most active time of year
allowing for maximum uptake of contaminates (Malmqvist 2002).
To assess toxicology, substrate samples were taken back to the lab and dried out for
examination. These samples were sealed and kept safe from atmospheric contamination. Once
dried, the samples were run for various compounds. Once these compounds were identified, the
samples were compared to those of other part of the river system. By doing so they were able to
get an idea of where certain compounds were leaching into this aquatic system (Chau 2007).
Acute toxicity of a troubled water system was assessed through the examination of fish and
invertebrates in the lab. Specimens were collected along the troubled river and marked for each
location. At the lab, each specimen was examined and screened for various toxins, particularly
heavy metal pollution. Both fish and invertebrates take up these toxins in their environment.
Through the examination and location markers, the team of scientists were able to pinpoint
specific location of pollutions along the waterway. This study was a great example of how you
can assess water quality through the examination of a water systems local fauna (Buckler, et el
2005).
7
Pharmaceutical pollution is a major concern to city water systems. Pharmaceuticals are
difficult to test for and react with other molecules in the water to form different compounds, thus
making it even more difficult. In a study done on several water ways along the east coast, aquatic
invertebrates were collected and tested in the lab. The focus of the study was to see how aquatic
invertebrate up took pharmaceutical pollution in their environment and how it affected them.
Challenges with the study were that there are hundreds of pharmaceuticals that could be tested
for, and once they react with water become other compounds, making it difficult to pinpoint.
This study did indicate that through assessment of aquatic invertebrates, much can be deciphered
about the quality of their water system (Williams, et el 2011).
Objectives
The main objective of this project is to determine how nearby storm-water retention ponds
affect water quality of Clear Creek near Prospect Park in Wheat Ridge, CO. It is important to
determine the sources of excess nutrients that cause harmful algal blooms in storm-water
retention ponds that discharge into the creek. It would be most beneficial to get a snapshot of
water quality in the creek before and after an algal bloom. Also, it will be helpful to assess the
macro-invertebrate populations in the area as indicators of water quality. Further, was the
eutrophication from the lakes and other surrounding ponds spreading into the Clear Creek basin?
8
Study Area
The study area was within Clear Creek near Prospect Park in Wheat Ridge, CO. The outlets
of two storm water retention lakes were chosen as sampling sites because of their proximity to
the Creek, and because the outlets were discharging directly into the creek. These lakes are
called Prospect Lake and Bass Lake. See provided maps for details.
Figure 1 - Denver Metropolitan Area
9
Figure 2 - Study Area, including labelled discharge canals
MATERIALS AND METHODS
On September 28, 2012 and November 2, 2012, our group collected data on water quality
and invertebrate life from Clear Creek in the Prospect Park area in Wheat Ridge, Colorado. Data
collection was carried out by using the proper materials, ideal sampling locations, and with the
utilization of optimal on and off-site sampling procedures. Water quality parameters that could
not be collected on-site were determined as soon as possible off-site. Statistical Analysis was
also conducted off-site. A snapshot of Clear Creek water quality up and downstream of
10
stormwater retention pond discharges is described herein as a result of our methods and use of
available materials.
Materials
The following materials were necessary for us to properly collect data:

Tagline

Vernier meter

Vernier probes

Non-Vernier temperature probe

Aquarium sampling kit

Catch net

Collection trays

Sample Collection Churn

Sample collection bottle

Sample bottles

Cooler

Waders

GPS

Lamotte Water Test Kit

YSI Meter
The materials that were most vital to our study are shown in Figure 1 below:
11
USGS Water Sampling Supplies
Vernier Meter and Probes
YSI Meter
LaMotte Water Analysis Kit
Figure 3 - Water Sampling Equipment used
Water Sampling Locations
The sample locations, or cross-sections, were carefully chosen at points in which there
was uniformity throughout the water column; mostly consistent depths; fewer riffles in the
water-flow; no obstructions in the cross-section; and away from split channels. These locations
are marked in Figure 2, and the criteria for choosing these locations are described below.
12
Figure 4 - Sampling Locations
For collection on September 28, samples were collected approximately 200 ft
downstream and 300 ft upstream of a discharge into the Creek from Prospect Lake. The Lake
was highly eutrophic, and the sampling point downstream of the discharge was saturated with
algae as a result. Samples were first collected downstream around latitude 39.77415, and
longitude -105.12679. The downstream collection was at latitude 39.77419, longitude 105.12873. These locations are seen in Figure 2 as “Downstream 1” and “Upstream 1”.
Photographs from the site locations are shown in Figure 3.
13
Downstream 1
Upstream 1
Figure 5 - Downstream and Upstream of Prospect Lake discharge into Clear Creek
For collection on November 2, samples were collected further west because the water
level in Prospect Lake was too low and there was no resultant discharge into Clear Creek (see
Figure 5). We moved further west and identified a discharge into Clear Creek from Bass Lake.
This discharge was clear, unlike the discharge noted earlier from Prospect Lake. Samples were
first collected approximately 400 ft downstream and 100 ft upstream of the lake discharge. The
sampling coordinates are approximately 39.77355,-105.13103 for the downstream location and
39.77386, -105.13298 for the upstream location. These locations are seen in Figure 2 as
“Downstream 2” and “Upstream 2”. Photographs from the site locations are shown in Figure 4.
14
Downstream 2
Upstream 2
Figure 6 - Downstream and Upstream of Bass Lake discharge into Clear Creek
15
Figure 7 - Comparison of water levels at the Prospect Lake discharge between sampling dates
Water Sampling and Invertebrate Identification Procedures On-Site
For the water sample collections, a tagline was drawn across from bank to bank at each
sampling location. Samples were then drawn into the sample collection bottle at 10 equally
measured intervals along the tagline. While drawing these samples, care was taken to ensure that
each interval was evenly sampled by descending and ascending the nozzle of the sample
collection bottle. Once the sampling bottle was full, it was carried to a partner on the bank with
clean gloves on, so they could dump it into the churn. After all sample water was collected in
the churn, it was agitated with the plunger and allowed to fill the sample bottles. These
16
techniques are illustrated in Figure 6 below. Four sample bottles were collected per location and
then immediately put on ice.
Setting up the Tagline
Collecting Water Samples
Use of Vernier Meter and Sample Collection
Churning Water Samples
Contents of kick screen into collection tray
Figure 8 - Sampling methods on-site
17
Meanwhile, the Vernier meter probes were placed into the water at each location to
measure pH, temperature, conductivity, and dissolved oxygen. After two minutes of adjustment
time, the data from the probes was recorded at 2 minute intervals for a total of 5 measurements.
In addition, a kick screen was used at each location to draw out aquatic invertebrates, which were
then placed into collection trays (Figure 6) and given an initial identification. Lastly, an
aquarium water sampling kit was used to determine pH, as well as levels of nitrites, nitrates,
ammonia/ammonium, copper, and calcium; by placing drops of water onto the testing strips.
Water Sampling and Invertebrate Identification Procedures Off-Site
Off-Site sampling procedures included the use of the Lamotte Water Test Kit, YSImultimeter, and aquatic invertebrate identification guides. The Lamotte Water Test Kit sample
procedure was carried out by placing 10 mL of a sample into the colorimeter bottle and ran as a
blank. After the blank, the samples were mixed with reagents and scanned again in the
colorimeter, which then outputted our nitrate as nitrogen or phosphate levels. This test was run
separately per indicator to test for phosphate and nitrite levels.
The YSI meter was used to test for dissolved oxygen, conductivity, nitrate levels, and
ammonia/ammonium levels. Sample water for each sampling location was placed into a clean
beaker and the YSI probe was placed into it, and then allowed to settle for a few minutes. Data
from the meter was recorded in 2 minute intervals for a total of 5 readings per sample.
Finally, aquatic invertebrates were identified via comparison to identification charts.
18
Aquatic Invertebrate Sampling
For sampling aquatic invertebrates, the process was simple and straight forward. We were
not continuing research already completed, nor were we comparing our research to that of
another study. For those reasons, we chose an inventory approach rather than a quantitative
approach.
Our inventory approach was to gather invertebrates without limiting the time we
roughed up the substrate, or how long we kept our net in the water. Our primary goal was to see
what species were present in general numbers, not what was present in each sample in exact
numbers to compare to another study on the same area.
We used a 6” x 12” fine mesh net purchased at an aquarium store. To observe the
invertebrates we used a 4” x 8” rectangle flat bottomed Tupperware container.
To sample, we chose shallow spots on decent flow and surface agitation. We sampled
several times in three zones: downstream, point source, and upstream. The net was held
perpendicular to the river bottom and roughed up the substrate up flow from the net for
approximately one minute. We filled our container with about an inch of water. We then dipped
the net into the container. Tweezers were used to remove any excess debris and algae that were
obstructing view. The container was left to settle for a couple of minutes before viewing. Upon
viewing we noted each species observed and made an approximate count of their numbers.
Statistical Analysis Off-Site
For those samples with multiple observations, statistical analysis was conducted with
MiniTab statistical software. This analysis is to determine whether or not the tested parameters
are statistically different downstream from upstream. The data is run through a two sample t-test
because there are not enough observations to run a z-test for normal distrib
19
RESULTS
Sampling Site 1 – Prospect Lake discharge into Clear Creek (9/28/2012)
Downstream
Results from sampling downstream of the Prospect Lake discharge into Clear Creek are
listed in Tables 1 – 3 below, and are separated by sample testing methods (on-site, YSI meter
readings, and Lamotte Water Testing kit).
Table 1 - On-site Vernier meter readings downstream of Prospect Lake
Time
1140
1145
1148
1150
1152
Average
St. Dev.
Temp
(°C)
19.4
19.2
19.3
19.4
19.4
19.34
0.09
pH
10.2
11.3
11.05
10.82
10.45
10.76
0.44
DO
Conductivity
(mg/L)
(uS/cm)
1.9
763
1.9
780
1.8
790
1.8
783
1.8
784
1.84
780.00
0.05
10.17
Table 2 - YSI meter readings from downstream of Prospect Lake
Time
1215
1218
1220
1222
1224
Average
St. Dev.
Temp Pressure
DO
Conductivity
(°C)
(mmHg) (mg/L)
(uS/cm)
17.9
627.7
5.21
693
17.9
627.9
4.84
694
18
627.9
4.8
695
18.1
627.9
4.71
697
18.2
627.9
4.63
700
18.02
627.86
4.84
695.80
0.13
0.09
0.22
2.77
20
NO3-N
NO3(mg/L) (mg/L)
11.59 51.30
11.25 49.79
11.52 50.99
11.79 52.18
12.1 53.56
11.65 51.56
0.32
1.40
Table 3 - Lamotte water test results from downstream of Prospect Lake
NO2-N (mg/L) NO2- (mg/L) PO43- (mg/L)
0.38
1.25
1.86
Upstream
Results from sampling upstream of the Prospect Lake discharge into Clear Creek are
listed in Tables 4 – 6 below.
Table 4 - On-site Vernier meter readings upstream of Prospect Lake
Time
1259
1301
1303
1305
1307
Average
St. Dev.
Temp
(°C)
20.2
20.2
20.3
20.3
20.3
20.26
0.05
pH
3.1
3.7
3.4
3.47
3.31
3.40
0.22
DO
Conductivity
(mg/L)
(uS/cm)
1.9
857
1.9
860
1.9
863
2.1
865
1.1
869
1.78
862.80
0.39
4.60
Table 5 - YSI meter readings from upstream of Prospect Lake
Time
1205
1208
1210
1212
1214
Average
St. Dev.
Temp Pressure
DO
Conductivity NO3-N
NO3(°C)
(mmHg) (mg/L)
(uS/cm)
(mg/L) (mg/L)
6.5
663
3.73 16.51
16.2
5.85
668
3.9 17.26
16.4
6.01
674
4.86 21.51
16.6
627.9
5.95
679
6.15 27.22
16.7
627.9
5.8
682
6.87 30.41
16.48
627.90
6.02
673.20
5.10 22.58
0.22
0.00
0.28
7.79
1.38
6.10
21
Table 6 - Lamotte water test results from upstream of Prospect Lake
NO2-N
(mg/L)
0.48
NO2(mg/L)
1.58
PO43(mg/L)
2.05
Notice that the results from Ammonia/Ammonium testing with the YSI meter are not
listed. These results are absent because the YSI meter consistently read “++++”, which indicates
over-range. Therefore, the only results for ammonia/ammonium are found with the aquarium
test strip results as indicated in Table 7 below. These test strips are intended to give the
aquarium maintainer a general idea of nutrient concentrations, and are not very precise for
scientific applications. The YSI meter may have been out of range, but it is also possible that it
was not calibrated or configured properly.
Also notice that the results for on-site pH and conductivity are significantly different
from downstream to upstream. It has been noted by peers and instructors that these particular
Vernier probes can be unreliable. For statistical analysis, the YSI meter readings for
conductivity were used instead. Also, the results from the aquarium test strips in Table 7 appear
to give a more realistic picture of the pH levels at Sample Site 1. These aquarium test strip
results are used in the results summary for Sample Site 1.
Alternative Water Quality Testing
Results from testing the water quality with an aquarium water testing kit on-site are listed
in Table 7 below.
22
Table 7 – On-site aquarium test kit results from Prospect Lake area
Sample Site
pH
Location
Up Stream
8.2
Point Source
Down Stream >8.8
NH3/NH4+
(mg/L)
4
4
4
NO2NO3(mg/L) (mg/L)
1
20
1
20
1
20
Aquatic Invertebrate Testing
Upon arrival and visual inspection of the river, we hypothesized that the aquatic
invertebrate count would be low as well as the species diversity. We did a preliminary
assessment of water quality using test kits from an aquarium store. Our results showed a
surprisingly high level of ammonia, 4 ppm mg/l. This result furthered our assumption.
Upon the first sample observed it was clear that a diverse group of aquatic invertebrate
inhabited this river. Once species were identified, it was clear that the river was indeed a good
habitat for aquatic invertebrate fauna. Sensitive invertebrates such as stoneflies and may flies
were present in large numbers as indicated in Table 8. These indicator species were present in
each sample taken in each of the three zones showing good consistency for their populations.
Excessively high numbers of aquatic planaria were present as well. These results indicate that the
river has abundant nutrients and food sources to support these populations and that water quality
is void of harmful amounts of pollutants and other toxins.
Results from the aquatic invertebrate counts upstream, downstream, and at the point of
the Prospect Lake discharge into Clear Creek, are listed below in table 8.
23
Table 8 – Aquatic Invertebrate counts in Prospect Lake area
Aquatic Invertebrates
Stone fly nymph
May fly nymph
Caddis Fly
Crane fly
Crayfish
Midge larva
Scud
Leach
Unidentified minnow
Planaria
Upstream
Point source Down Stream
42
36
32
14
7
12
12
8
9
0
0
1
1
0
0
7
12
6
13
15
11
1
1
0
3
1
0
56
43
61
Sampling Site 2 - Bass Lake discharge into Clear Creek (11/2/2012)
Downstream
Results from sampling downstream of the Bass Lake discharge into Clear Creek are listed
in Tables 9 – 11 below, and are separated by sample testing methods.
Table 9 - On-site Vernier meter readings downstream of Bass Lake
Time
1404
1406
1408
1410
1412
Average
St. Dev.
Temp
(°C)
17
17.1
17.1
17.1
17.2
17.10
0.07
24
pH
7.5
7.96
8.12
8.18
8.23
8.00
0.30
Table 10 - YSI meter readings from downstream of Bass Lake
Time
1600
1602
1604
1606
1608
Average
St. Dev.
Temp Pressure
DO
Conductivity
(°C)
(mmHg) (mg/L)
(uS/cm)
7.8
631.3
8.9
654
7.9
631.3
8.8
656
8
631.3
8.8
659
8.2
631.3
8.8
662
8.4
631.3
8.7
665
8.06
631.30
8.80
659.20
0.24
0.00
0.07
4.44
NO3-N
(mg/L)
46.3
49.64
30.11
28.84
30.9
37.16
9.97
NO3(mg/L)
204.93
219.71
133.27
127.65
136.77
164.47
44.12
Table 11 - Lamotte water test results from downstream of Bass Lake
NO2-N
(mg/L)
0.36
NO2(mg/L)
1.18
PO43(mg/L)
2.15
Upstream
Results from sampling upstream of the Bass Lake discharge into Clear Creek are listed in
Tables 12 – 14 below.
Table 12 - On-site Vernier meter readings upstream of Bass Lake
Time
1442
1444
1446
1448
1450
Average
St. Dev.
Temp pH
(°C)
17.7
7.91
17.7
8.11
17.7
8.17
17.7
8.23
17.7
8.24
17.70
8.13
0.00
0.13
25
Table 13 - YSI meter readings from upstream of Bass Lake (taken
Time
1612
1614
1616
1618
1620
Average
St. Dev.
Temp Pressure
(°C)
(mmHg)
7.5
631.2
7.6
631.2
7.8
631.2
8
631.1
8.2
631.1
7.82
631.16
0.29
0.05
DO
Conductivity
(mg/L)
(uS/cm)
8.1
650
7.8
651
7.7
656
7.7
659
7.7
664
7.80
656.00
0.17
5.79
NO3-N
(mg/L)
21.43
20.37
19.85
21.03
23.98
21.33
1.60
NO3(mg/L)
94.85
90.16
87.86
93.08
106.14
94.42
7.08
Table 14 - Lamotte water test results from upstream of Bass Lake
NO2-N
(mg/L)
0.28
NO2(mg/L)
0.92
PO43(mg/L)
2.23
For Sample Site 2, fewer Vernier probes were used due to unreliability. However, the
Vernier pH probe results did appear to be accurate this time.
DISCUSSION
Statistical Analysis
The data collection results, with the exception of those that were taken from the Lamotte
colorimeter, consisted of 5 observations for both upstream and downstream at both sample sites.
Since there were less than 30 observations each, a two sample t-test was performed using the
following hypothesis test and level of significance:
26
The t-value test statistic, p-value, and level of significance were collected for the pH,
nitrate, and conductivity observations, and are shown in Table 15 below.
Note that all
parameters are statistically significant during the first sample collection, where highly eutrophic
discharge was visibly evident.
Table 15 - Statistical Analysis of Water Sample Results
pH
NO3Conductivity
Sample Site 1 –
Prospect Lake discharge
tpsignificance
value value
Significant
-33.25 0.000
Difference
Significant
-10.34 0.000
Difference
Significant
-6.11
0.004
Difference
tvalue
1.01
Sample Site 2 –
Bass Lake discharge
psignificance
value
No Significant
0.371
Difference
-3.51
0.025
Significant Difference
-0.98
0.359
No Significant
Difference
Parameters noted in Table 15 for Sample Site 2 are not statistically significant with the
exception of nitrates. However, had we chosen a level of significance of 0.02, we could then be
98% sure that there was no statistically significant difference between the true means of pH,
nitrates, and conductivity at Sample Site 2 at the time of collection; with the opposite being true
for Sample Site 1.
Results Summary
The results of sample testing downstream and upstream at both sites are summarized
side-by-side in table 15 below.
27
Table 16 – Side-by-side results summary from both sites
pH
Conductivity
(uS/cm)
NO3- (mg/L)
NO2- (mg/L)
PO43- (mg/L)
Sample Site 1
Sample Site 2
Upstream Downstream Upstream Downstream
8.2
> 8.8
8.13
8.0
673.2
695.8
656
659.2
22.58
1.58
2.05
51.56
1.25
1.86
94.42
0.92
2.23
164.47
1.18
2.15
The reported pH levels for Sample Site 1 are taken from the aquarium testing strip
because the Vernier probe at the time was suspected of giving bad results. Regardless, the pH
downstream would have certainly been higher downstream than upstream, because algae is
known to increase pH levels (Bitton, 2011).
Finally, nutrient levels from both sampling locations/dates are illustrated in Figure 7
below, shown with a base 10 logarithmic scale.
Figure 9 - Graph of Sampling Site Nutrient Levels
28
Legal Compliance
Despite our summary of information, it is important to note that at the time of initial
sampling, the City of Wheat Ridge was in compliance with local and federal laws. The EPA’s
National Pollutant Discharge Elimination System (NPDES) permits, part of the EPA’s Clean
Water Act, do not require specific nutrient monitoring from point-source stormwater discharges
(EPA, 2012). The Phase II Stormwater Rule created by the EPA in 1999, also does not contain
such stipulations. These regulations generally include public education/outreach/involvement,
detecting and eliminating illicit discharges, construction and post construction run-off control,
and pollution prevention (City of Wheat Ridge, 2012). The purpose of these objectives is to
reduce polluted runoff, but not necessarily to monitor nutrients from a point-source stormwater
discharge into creeks.
Cladophora
It was determined that the algae being discharged from Prospect Lake is a filamentous type
of algae that is part of the phylum Ulvophyceae. It often dominates periphyton communities and
can produce nuisance growth problems during eutrophic conditions (AlgaeBase). The algae was
identified by visual inspection and it was noted that it had rather large filaments and
dichotomously branched makeup. Further microscopic investigation was required to identify the
species type, but unfortunately the samples sat for too long and the algae decomposed in the
sample bottle. Using the photographic evidence of the algal bloom, an educated guess would
pinpoint the species as Cladophora glomerata. This species has mainly been causing problems
in the Great Lakes region, but is widespread in many freshwater ecosystems including Colorado
streams and reservoirs (Young et al 2012). Uncontrolled blooms are caused by excessive
29
nutrients (such as phosphorus) present within the water and the high nutrients are often attributed
to anthropogenic sources such as urbanization, wastewater treatment, and agriculture. However,
this species is attributed be more of a nuisance to humans rather than harmful to the ecosystem as
a whole. There are even some beneficial aspects of the algae that include providing suitable
habitat for aquatic invertebrates, uses in ecological engineering, and production of biofuels
(Zulkifly et al 2012). Year round monitoring should be required in order to get a better
understanding of the impacts the algae is having on downstream communities.
Aquatic Invertebrates
As discussed in the results section, aquatic invertebrate work as an indicator species for
aquatic contaminates. Easily collected and observed, they make ideal specimens for research and
quick assessment in the field. Prospect Park may not appear visually to have the water quality to
support high levels of aquatic life but our sampling process proved otherwise. After assessing the
results, this section of Clear Creek is a good habitat for supporting a large number of aquatic
invertebrates and other aquatic life such as juvenile fish. More in depth studies would have to be
performed to detail why we found such an abundance of planaria compared to other invertebrates
and to pin point what nutrients and food are present that are supporting these large populations.
Further studies that would help to assess water quality might entail taking the invertebrates back
to a lab and assessing them for uptake of toxins. It is well studied that aquatic invertebrates
intake toxins present in their environment (Buckler, et el 2005).
30
CONCLUSION
The goal of our field study was to find out how much affect, if any, eutrophication of the
wet pond Prospect Lake in Prospect Park had on Clear Creek water quality. Data collection for
sample site 1 (Prospect Lake discharge) occurred on 9/28/12. After compiling data from this
field study, we ventured out and collected a second sampling from a differing site, sample site 2
(Bass Lake discharge) on 11/2/12, and used this data to compare findings about the area. There
were downstream and upstream samples for each point of discharge from Prospect Lake and
Bass Lake. This was done to see whether there was a significant amount of nutrients such as
nitrates and phosphorous, high pH, low levels of DO, and unhealthy temperature and
conductivity levels downstream from the point of discharge which would indicate whether the
eutrophication of Prospect Lake had an effect on water quality to Clear Creek. Bass Lake was
used as a comparison as it was not showing signs of eutrophication. Aquatic invertebrate
sampling was performed in the same manner as an indicator of water quality.
Although eutrophication is a natural process, we were concerned with how much
anthropogenic causes were contributing to this process in Prospect Lake. If the process is
occurring too rapidly, and is not being monitored and treated, then it can have a direct impact to
the habitat of the area and the water contained and flowing through it. In addition to taste and
odor concerns associated with excess algae production, elevated levels of total organic carbon
are an increasing concern because of the harmful and strictly regulated disinfection by-products
that result from chlorinating water high in TOC. As observed, Prospect Lake is surrounded by
concrete, an RV park, dog kennel, and a landscape that is treated with pesticides and fertilizers. It
does not contain much of a natural wetland environment. Alternately, Bass Lake which is
surrounded by a marshy area does not contain nearly as much algae, so it is more than likely
31
much better at filtering out pollutants and nutrients. Also, Bass Lake’s discharge is continually
and slowly released which helps in the filtering process, while Prospect Lake is discharged a
couple of times a year with large amounts at once. Taking this into account, Bass Lake could
potentially be used as a reference in improving Prospect Lakes’ filtering capabilities.
It can be concluded that although we received higher readings for nitrates from Bass Lake,
this was most likely due to algae in Prospect Lake consuming the nutrient. Also, there were
higher levels of phosphates downstream from both lakes, with Prospect Lake containing slightly
less than Bass Lake. A possible reason for the unexpected higher amount of phosphates
discharging from Bass Lake, considering its minimal amounts of algae, might correlate with the
sampling of this site being conducted a few weeks later from the date of sampling of the first
site. Furthermore, there had not been much precipitation and the temperatures were still
considerably warm, so what was accumulated in the lakes had been sitting for a while without
having been cycled.
In addition we also found a significant amount of aquatic invertebrates in this portion of
Clear Creek. This would imply that the water in the creek is not as polluted and toxic as we
initially thought. In fact, it can be concluded that water conditions are good for supporting
aquatic life. There appeared to be good food sources and plenty of nutrients for aquatic
invertebrates to consume. Studies have shown that aquatic invertebrates from the top tear can
handle a decent amount of pollution.
After completing our study and evaluating the results, it can be concluded that the
retentions ponds near clear creek need improvement of monitoring and design in order for them
to perform better in naturally filtering out these nutrients. Further study of the area can help in
32
solidifying this conclusion. As with any study, there was room for improvement within our
methods. Stricter and more precise lab methods for analysis and protocols for taking field
samples could have been employed for better results, but this would have cost more money than
we had available for our purposes. Also, the field equipment could have been better calibrated
for greater accuracy in field tests. Additionally, year round sample gathering would present a
better picture of cycling of nutrients through the system in the study area. The samples were
gathered in the fall, when algal bloom does normally occur with “fall overturn”, but it also
occurs, and normally to a greater degree, in the spring (Wright, 1993). Year round study could
produce more enhanced and well rounded results. There were definitely way to improve our
study, but with all things considered, we gathered sufficient enough data to obtain results and
conclusions for this study.
Interestingly enough, it seems we were not the only ones with an attitude toward
monitoring nutrient levels discharged into the creek by stormwater ponds. The Colorado
Department of Public Health and Environment introduced Regulation 85 effective September 30,
2012. This regulation affects localities with point-source stormwater discharges into streams, of
which, Wheat Ridge has a permit to do so. As outlined in Regulation 85.6 (3)(c), the State’s
Municipal Separate Storm Sewer System (MS4) permittees must submit a discharge assessment
report by October 31, 2014. This report shall; “Allow for the determination of representative
estimates that quantify MS4 discharge flows and associated concentrations, and loads of total
nitrogen and total phosphorus from the permittee’s MS4. This shall include representative annual
or seasonal information to define significant nutrient loads from different land uses due to
rainfall events, snowmelt events, and/or dry weather flows.” (CO Dept. of Public Health & Env,
2012). Note that both total nitrogen and phosphorus concentrations will be part of this
33
monitoring objective, which is just what we set out to do with our project. It is good to know
that the environmental consensus in our state is leaning in the right direction by going above and
beyond EPA standards.
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Acknowledgements
C. Burt – Figures, tables, and content from Materials, Methods, Results, and Discussion (except
for Aquatic Invertebrates and tables 6 and 7), plus Regulation 85 in Conclusion (last paragraph)
A. Keiswetter – All aquatic invertebrate writings contained within Literature Review, Methods,
Results, and Discussion.
L. Eagle – Title, Abstract, Keywords, and Introduction
E. Newman – Literature Review (wet ponds), Objectives, Study Area, Cladophora writing
contained within Discussion, and Poster
I. Sleeger – Conclusion
37