HomeMy WebLinkAboutMemo - Mail Packet - 2/20/2024 - Memorandum From Diana Schmidt Re: 2023 Fall Water Quality Update – Upper Cache La Poudre Watershed (3)Utilities
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700 Wood Street
PO Box 580, Fort Collins, CO 80522
970-221-6700
utilities@fcgov.com
CC: Jason Graham, Director of Water Utilities
Jill Oropeza, Senior Director of Water Planning and Sciences, Utilities
Leslie Hill, Director of Water Quality Services Division, Utilities
Richard Thorp, Watershed Program Manager, Utilities
Water Commission
MEMORANDUM
Date: January 25, 2024
To: Mayor Arndt and City Councilmembers
Through: Kelly DiMartino, City Manager
Tyler Marr, Acting Utilities Executive Director
From: Diana Schmidt, Watershed Specialist
Subject: 2023 Fall Water Quality Update – Upper Cache la Poudre Watershed
BOTTOM LINE
The Upper Cache la Poudre (CLP) Watershed Collaborative Water Quality Monitoring Program
is a partnership between the cities of Fort Collins, Greeley, Thornton, and Soldier Canyon Water
Treatment Authority. The goal of this monitoring effort is to assist program participants with
meeting current and future drinking water treatment goals by reporting current water quality
conditions and trends within the Upper CLP Watershed. The attached water quality update
provides a summary of weather, drought, streamflow, and water quality conditions observed in
the Upper CLP watershed during the 2023 fall season.
BACKGROUND
Seasonal reporting for this program is published for the spring, summer, and fall seasons. The
seasonal water quality updates are designed to inform the Upper CLP Watershed Collaborative
Monitoring Program partners, their customers, and other community stakeholders about the
condition of our source watershed and the quality of the raw drinking water supply. In-depth
water quality trend reporting is done through annual and five-year technical reports. Water
quality reports and seasonal updates are made publicly available on the Fort Collins Utilities’
website, https://www.fcgov.com/utilities/what-we-do/water/water-quality/source-water-
monitoring/upper-poudre-quality-monitoring.
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FALL 2023 WATER QUALITY UPDATE HIGHLIGHTS
Fall is a season when streamflow on the Poudre River transitions to baseflow levels (or low
flow). Water quality during this time of the year is generally stable throughout the Upper CLP
Watershed. However, water releases from high elevation water storage reservoirs may cause
changes in streamflow and water quality during September and early October, although these
events are temporary.
The Upper CLP Watershed experienced temperatures above the historic average, while both
precipitation and streamflow were below average. Water quality indicators measured at key
long-term monitoring sites were within expected ranges. However, average water temperature,
pH, and conductivity at several sites were somewhat elevated, which can likely be attributed to
the hot and dry conditions observed during the 2023 Fall Season.
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Upper Cache la Poudre Watershed Collaborative Monitoring Program
FALL 2023 WATER QUALITY UPDATE
Source Water Monitoring
The Upper Cache la Poudre (CLP) Watershed Collaborative Water Quality Monitoring
Program was established in 2008 between the cities of Fort Collins, Greeley and Soldier
Canyon Water Treatment Authority, to help meet present and future drinking water
treatment goals. The City of Thornton joined the collaborative as a full partner in 2022.
Water quality monitoring of our raw, CLP River drinking water supply is conducted from
April through November. Monitoring sites are strategically located throughout the Upper CLP
watershed. Water quality data provide valuable information about the health of our source
watershed and quality of the CLP raw water supply.
The Fall 2023 Water Quality Update provides a seasonal summary of watershed conditions
in the Upper CLP watershed by highlighting weather, drought, streamflow, and water quality
conditions over the fall season (September – November).
Routine water quality monitoring results are reported for six key monitoring sites located
throughout the Upper CLP watershed, which capture water quality conditions above and
below major tributaries and near water supply intake structures (Figure 1). Fall 2023 water
quality data are compared to baseline water quality data, collected between 2008 to 2012.
Figure 1 – Upper Cache la Poudre
Watershed Collaborative Monitoring
Program water quality sampling
sites.
JWC - Joe Wright Creek above the
confluence with the Poudre River
PJW - Poudre River above the
confluence with Joe Wright Creek
PBR - Poudre River below Rustic
PSF - Poudre River below the
confluence with the Little South Fork
PNF - Poudre River above the
confluence with the North Fork at
the City of Fort Collins’ Intake
PBD - Poudre River below the
confluence with the North Fork at
the Bellvue Diversion
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Temperature
Air temperature measured at the Joe Wright Snowpack Telemetry (SNOTEL) station over the 2023 fall season was 2.6°F warmer than
the long-term average and ranked as the 8th warmest fall on record (out of 34 years). Monthly mean air temperature was above
average in September and October and well above average in November. The month of November was 4.1°F warmer than the long-
term average and ranked as the 10th warmest on record (Table 1).
Temperature
2023
(ºF)
Average
(ºF)
Departure
(ºF)2023 Rank
September 46.9 44.7 +2.2 14th (H)
October 36.5 34.7 +1.8 12th (H)
November 28.9 24.8 +4.1 10th (H)
Fall 37.4 34.9 +2.6 8th (H)
Precipitation
Precipitation measured at the Joe Wright SNOTEL over the 2023 fall season was below average and ranked as the 2nd driest fall on
record (out of 45 years). Precipitation was below average in all months. The month of November was particularly dry and ranked as
the fourth driest on record. Precipitation measured only 45% of the average in November (Table 2). Drought conditions returned to
the Upper CLP watershed over the fall season due to above average temperatures and below average precipitation measured from
September-November. Drought conditions intensified from no drought at the start of the fall season to abnormally dry conditions in
the northern portion of the CLP watershed by the end of the fall season (Figure 2).
Total Precipitation
2023
(inches)
Average
(inches)
% of
Average 2023 Rank
September 1.4 2.8 50%11th (D)
October 3.0 3.9 77%15th (D)
November 1.9 4.2 45%4th (D)
Fall 6.3 10.8 58%2nd (D)
Table 1 – Monthly mean air temperatures
measured at the Joe Wright SNOTEL over
the fall months of 2023 compared to the
long-term average (1991 – 2020)
Note: H = hottest and C = coldest
Table 2 – Monthly accumulated precipitation totals
measured at the Joe Wright SNOTEL over the 2023
fall season compared to the long-term average
(1991 – 2020).
Note: W = wettest and D = driest
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Figure 2 – Drought conditions for the state of Colorado as monitored by the United States Drought Monitor on August 29, 2023 (left) and
November 28, 2023 (right). (Map source: https://droughtmonitor.unl.edu/)
Streamflow Conditions
Streamflow at the Cache la Poudre River near the Canyon Mouth (CLAFTCCO) stream gage measured 11,458 acre-feet of water over
the fall season, which was 63% of the long-term average (calculated over the 1881 – 2022 measurement period). The total amount of
water measured near average in November, below average in October, and notably below average in September when streamflow
measured only 40% of average (Figure 3). The low September flows could be due to a combination of below average precipitation,
high temperatures leading to increased evapotranspiration, and changes in high elevation water storage within the Upper CLP.
Additionally, the monthly average flow varied by only ~200 acre-feet between the fall months, which is notably lower than the long-
term variation (Figure 3). This discrepancy alludes to changes in high elevation water storage and increased water demand. Stream
gages below each high elevation reservoir (LAPLODCO, JWCCHACO, CLANSECO) confirm that Long Draw Reservoir releases ceased
in October, Chambers Reservoir releases ramped down in October, and Seaman Reservoir releases remained constant through the
fall months. The demand for treated water was also high due to dry, hot conditions resulting in increased raw water diverted from
the Poudre River at Fort Collins and Greeley’s intakes located upstream of the Canyon Mouth gage.
Figure 3 –
Streamflow
conditions on
the Poudre River
over the 2023
fall season (left)
and monthly total
water volume
measured over the
summer season
(right).
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Fall monitoring captures water quality as streamflow on the Poudre River transitions to baseflow (or low flow) conditions. During
this time of the year water quality is generally stable throughout the watershed. Water releases from high elevation water storage
reservoirs and storm events may cause changes in streamflow and water quality through September and early October, although
these events are temporary. Substantial water releases in the Upper CLP watershed typically cease (depending on demand) in
October, and storm events this time of year are more uncommon, as precipitation in the Upper CLP shifts from rain to snow. Most
water quality constituents begin to concentrate under baseflow conditions and water temperature decreases, especially in the higher
elevations of the watershed.
Water Quality Indicators
The Upper CLP Collaborative Water Quality Monitoring Program uses several key water quality indicators, including pH, conductivity,
temperature, and turbidity, which act as surrogates for other parameters (Table 3). These indicators provide a snapshot of water quality
conditions and are useful for identifying trends or changes in water quality. Significant changes in these water quality indicators may
provide an early warning of potential water pollution.
Water Quality Indicator Explanation
Temperature
Water temperature influences other water quality parameters and is a
major driver of biological activity and algal growth in rivers, including
certain phytoplankton species that produce the taste and odor
compounds, geosmin and 2-methlyisoborneol.
pH
pH is an important water quality parameter to monitor, because
it influences the solubility and biological availability of chemical
constituents, including nutrients and heavy metals. pH near 7 is
considered neutral, with more acidic conditions occurring below 7 and
more basic, or alkaline, conditions occurring above 7.
Specific Conductivity
Conductivity is an index of dissolved ionic solids in water. Conductivity
is used as a general measure of water quality. Significant increases in
conductivity can be used as an indicator of increased pollution.
Turbidity
Turbidity is monitored to track changes in water clarity. Clarity
is influenced by the presence of algae and/or suspended solids
introduced to surface waters through various land use activities,
including runoff and erosion, urban stormwater runoff and drainage
from agricultural lands. For water treatment, turbidity is an important
indicator of the amount of suspended material that is available
to harbor pollutants, such as heavy metals, bacteria, pathogens,
nutrients and organic matter.
Table 3 – Water
quality indicators
measured as part of
the Upper Cache la
Poudre Collaborative
Water Quality
Monitoring Program.
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Joe Wright Creek Canyon Mouth
Over the fall months of 2023, all water quality indicators at
key sites along the CLP River were within the baseline range
of values (Figure 4). Water temperature was above normal
at all key monitoring sites – normal is defined as the median
value over the baseline period of record. pH was at or slight-
ly below normal at higher elevation monitoring sites on Joe
Wright Creek (JWC) and the Poudre River above Joe Wright
Creek (PJW). pH measured slightly above normal from
the Poudre below Rustic (PBR) downstream to the City of
Greeley’s raw water intake (PBD). Specific conductivity was
higher than normal at all key sites. Turbidity measured within
the baseline range of values at all monitoring sites. Lower
than average flow conditions in September and October
likely contributed to the increase in water temperature, pH,
and conductivity observed in the fall months.
Diana Schmidt, Watershed Specialist with the City of Fort
Collins, collects water samples from the mainstem Cache
la Poudre River (PNF).
Figure 4– Water quality
indicator data collected
at key monitoring
sites over the 2023
fall monitoring season
(September, October,
and November)
compared to baseline
fall water quality
conditions.
Fall 2023
Median
Maximum
Median
Minimum
Graphic Explanation
Baseline data
range based
on long-term
data record
2008-2012
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Summary
The Upper CLP experienced hotter and drier than average conditions during the fall months of 2023. Combined with high elevation
water storage and increased treated water demand, these conditions likely exacerbated the low flow conditions observed at the
Poudre Canyon mouth during September and October. During all fall months, water quality indicators at key sites along the CLP River
were within the baseline range of values. Though within the baseline, increases in water temperature, conductivity, and pH (at lower
elevation sites) were observed across the Upper CLP. This departure from the baseline is likely due to the observed low flow conditions.
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