Streamgage Summary

This study incorporated daily streamgage data for baseflow and flood-frequency modeling from four streamgages in the study area (table 1). The conductivity mass balance method used to estimate baseflow requires daily streamflow and SC data which are available at three streamgages above East Canyon Reservoir on East Canyon Creek (fig. 2): (1) USGS streamgage 10133650, E Canyon CR BL I-80 Rest Stop NR Park City, UT; (2) USGS streamgage 10133800 East Canyon Creek Near Jeremy Ranch, UT; and (3) USGS streamgage 10133980 East Canyon Creek AB East Cyn Res NR Morgan, Utah (U.S. Geological Survey, 2024). Effluent data from the ECWRF (Root, 2025), including monthly TDS and daily discharge, also were incorporated into the calculation at downstream USGS streamgages 10133800 and 10133980. The method used to determine flood frequency, namely the Expected Moments Algorithm (England and others, 2018), requires only discharge monitoring, allowing for the streamgage on McLeod Creek to be included in the analysis (USGS streamgage 10133600, Mcleod Creek Near Park City, UT).

The most upstream streamgage in the reach with daily discharge and SC is USGS streamgage 10133650 (E Canyon CR BL I-80 Rest Stop NR Park City, UT). The streamgage is located immediately downstream from where I-80 crosses over McLeod Creek and below the confluence with Kimball Creek and represents a drainage area of 42.1 square miles (mi²). The site was established on October 31, 2002, for continuous discharge monitoring and discrete data collection, which began on November 7, 2002. The streamgage was updated in May 2010 to continuously measure SC, pH, and dissolved oxygen. The streambed comprises cobbles and gravel at the location of the streamgage, and the channel emerges from two 8-foot (ft) culverts approximately 100 ft upstream. A thick growth of riparian vegetation and other aquatic plants typically develops along the streambank during the late summer and early fall months before moderate to heavy ice builds over the stream during the winter. Because McLeod and Kimball Creeks join just upstream and may not be fully mixed at the streamgage, SC values may be skewed during high-flow events. This streamgage is likely exposed to anthropogenic contaminants including road salt from I-80 (Brooks and others, 1998).

U.S. Geological Survey streamgage 10133800 (East Canyon Creek Near Jeremy Ranch, UT) is approximately 4 miles (mi) downstream from USGS streamgage 10133650 and has a drainage area of 57.2 mi². The streamgage is located on the Jeremy Ranch Golf and Country Club property just downstream from a culvert and the ECWRF. This streamgage records continuous discharge, SC, pH, water temperature, and dissolved oxygen. The streamgage was moved approximately 100 yards downstream in April 2016 due to poor mixing between ECWRF releases and natural streamflow at the site. The streambed comprises mostly cobbles, and the channel is straight above and below the streamgage as the stream flows from an 8-ft culvert. The streambanks are steep and covered with large rocks and vegetation including willows. Ice does not typically build during the winter due to constant warm-water releases from the ECWRF.

U.S. Geological Survey streamgage 10133980 (East Canyon Creek AB East Cyn Res NR Morgan, Utah) is approximately 10 mi downstream from USGS streamgage 10133800. This streamgage records continuous discharge, SC, pH, dissolved oxygen, and water temperature and is immediately upstream from East Canyon Reservoir on East Canyon Resort property and represents a 107 mi² drainage area. The streambed comprises cobbles at the site of the streamgage, with a channel that is straight above and below. A bridge is immediately upstream and constricts flow at the site of the streamgage. The banks are steep and covered with large rocks, willows, and other vegetation. Considerable ice builds along the shore during the winter months, typically between December and February.

U.S. Geological Survey streamgage 10133600 (Mcleod Creek Near Park City, UT) is the most upstream streamgage in the watershed and is approximately 4 mi upstream from USGS streamgage 10133650. The streamgage has measured daily discharge since October 1990 but is not used for baseflow estimation in this study because SC is not measured at this site. The streambed consists of gravel and small- to medium-sized cobbles, and the channels are heavily vegetated with small willows that can constrict the channel and inhibit flow at the streamgage.

Snow Telemetry Stations

The Natural Resources Conservation Service operates two SNOTEL stations located within the study area above East Canyon Reservoir at Parleys Summit (site no. 684; 7,585 ft in altitude) and Thaynes Canyon (site no. 814; 9,230 ft in altitude; table 2). The Parleys Summit station has reported snow-water equivalent (SWE), daily precipitation, and cumulative precipitation since October 1, 1978; minimum, maximum, and mean daily temperature data were added on May 5, 2003. Thaynes Canyon has reported SWE, daily precipitation, and cumulative precipitation since October 1, 1987; minimum, maximum, and mean daily temperature data were added on June 21, 2004. The Parleys Summit and Thaynes Canyon SNOTEL station data may be accessed through the U.S. Department of Agriculture (USDA) Natural Resource Conservation Service (NRCS) National Water and Climate Center (NWCC) Air and Water Database website at https://wcc.sc.egov.usda.gov/nwcc/site?sitenum=684 and https://wcc.sc.egov.usda.gov/nwcc/site?sitenum=814, respectively (U.S. Department of Agriculture, National Water and Climate Center, 2025). A third site, the Hardscrabble SNOTEL station (site no. 896; 7,250 ft in altitude), drains into East Canyon Creek below East Canyon Reservoir and is not considered for this study.

Baseflow Estimation by Conductivity Mass Balance Hydrograph Separation

The baseflow component in East Canyon Creek was estimated at a daily timestep using a conductivity mass balance hydrograph separation approach. Streamflow (Q) and SC data required for hydrograph separation were obtained from the USGS National Water Information System (NWIS) online database (U.S. Geological Survey, 2024). Each respective streamgage record was truncated to the nearest complete water year (WY) on record to reduce seasonal bias. A water year is the 12-month period from October 1 through September 30 of the following year and is designated by the calendar year in which it ends. For sites 10133800 and 10133980, which are downstream from the ECWRF, the records are truncated from October 1, 2008, to September 15, 2022, to coincide with the earliest and last available effluent data.

The conductivity mass balance approach is best suited for sites that meet criteria outlined by Miller and others (2014) and Rumsey and others (2015). The summarized criteria that apply to this study include (1) an inverse relation between Q and SC as described by a power function; (2) annual peak discharge coinciding with snowmelt runoff during the spring–summer months, typically between March and June, and is an order of magnitude greater than low-flow conditions; (3) a wide range of SC values throughout the year, with the minimum approaching the runoff end-member; and (4) streamgages must be at least 2 kilometers (km) downstream from a reservoir. The streamgages used in this study did not fully satisfy the first criteria, so additional steps were taken to compensate. With respect to the first criteria, Q and SC showed an inverse relation only during the summer (May–August) and fall–winter months (September–January), with an early spring runoff (February–April) deviation (fig. 3) that may be related to anthropogenic contaminants, including road salt. Data during this spring runoff interval were excluded from the baseflow estimation to reduce the potential anthropogenic influence on the model during expected periods of runoff and characterize a more natural representation of East Canyon Creek.

Daily baseflow was estimated for the period of record at each streamgage using a two-component mass balance approach (Pinder and Jones, 1969):

The USGS streamgage below I-80 (10133650) uses only streamgage Q and SC data. Effluent from the ECWRF impacts both the Q and SC records at downstream USGS streamgages (10133800 and 10133980) and is accounted for by a nested mass balance of effluent Q and SC. Monthly total effluent volumes were converted to daily mean effluent Q (in ft³/s) by linear interpolation. Monthly mean effluent TDS (in mg/L) were linearly interpolated to daily mean effluent TDS and were then converted to SC (in µS/cm at 25 °C) using the ratio of TDS to SC, which is typically between 0.5 and 0.9 (Hem, 1985; U.S. Geological Survey, 2019). Due to the proximity of USGS station 10133800 and the ECWRF, the ratio between TDS to SC was established by comparing days where the effluent discharge was nearly equal to the measured discharge of East Canyon Creek. The ratio of TDS to SC on those days was approximately 0.7; this ratio was used to estimate SC for the remainder of the TDS record. Streamgage Q and SC data from the two East Canyon Creek stations (USGS streamgages 10133800 and 10133980), downstream from the ECWRF, were corrected for effluent Q and SC by mass balance using the equations below:

By accounting for effluent in the streamgage record, the modified conductivity mass balance was used for baseflow estimation at USGS streamgages 10133800 and 10133980:

The runoff end-member (SC_RO) represents an estimate of the low-SC surface or near-surface waters that flow into East Canyon Creek and has not been measured in the Wasatch Mountains. Another study in the Upper Colorado River Basin estimated the SC_RO in snowmelt-dominated hydrological systems at 33 µS/cm at 25 °C (Miller and others, 2014). Because Miller and others (2014) was based on high-elevation catchments that drain small watersheds during runoff analogous to the Snyderville Basin, 33 µS/cm at 25 °C runoff was used in this study as the SC_RO.

The annual estimate of baseflow SC was estimated by calculating the 95th percentile of daily SC values (SC_GAGE for 10133650, eq. 1; SC_ECC for 10133800 and 10133980, eqs. 2, 4) for each water year on record. This annual baseflow SC omitted data from the spring runoff period (February–April) because that period deviates from the inverse relation of SC and Q. The annual 95th percentile estimates of SC_BF were linearly interpolated to derive a daily baseflow end-member (SC_BF; eq. 1) for the period of record, including during the spring runoff months. Mean daily values for baseflow and streamflow are the mean values of each day of the year from January 1 to December 31 over the period of record. The baseflow index (BFI) is the ratio of total baseflow to total streamflow and was calculated annually for each streamgage. Seasonal BFI also was determined in order to highlight the effect of varying hydrologic conditions on baseflow.

The conductivity mass balance method includes three assumptions: (1) no additional streamflow inputs beyond those described above contribute to streamflow; (2) SC_RO is a constant; and (3) SC_RO and SC_BF are significantly different (Sklash and Farvolden, 1979; Miller and others, 2014). For streamgages affected by effluent from the ECWRF, SC_RO, and SC_BF are further assumed to be significantly different than SC_EFF.

Trend and Correlation Analysis for SNOTEL and Streamflow Data

Daily data for WYs 2011–22 from SNOTEL and streamgage records were used to develop annual and monthly trends and correlations. Only datasets with years that include data for every month in a water year were considered. For SNOTEL data, daily metrics for SWE, precipitation, and temperature were used. Daily SNOTEL data were compiled using the snotelr package for R (Hufkens, 2022). Annual and monthly variables derived from streamgage data include mean discharge, mean baseflow, and mean BFI. These data are available as a data release at https://doi.org/10.5066/P14SJDMX (Root, 2025).

Flood Frequency

Flood frequency analyses were done on East Canyon Creek and McLeod Creek to estimate the Pearson Type III distribution parameters and determine flood frequency. The Expected Moments Algorithm provides a direct fit of the distribution using annual peak streamflow data (fig. 4) and adjustments for potentially influential low floods; these methods are detailed in USGS Bulletin 17C (England and others, 2018). The companion software program developed by the USGS (Flynn and others, 2006; Veilleux and others, 2014), PeakFQ (version 7.4.1), uses annual peak flows to calculate annual exceedance probabilities. Although the streamgage records on East Canyon Creek at USGS streamgages 10133650 (WY 2003), 10133800 (WY 2002), and 10133980 (WY 2008) are relatively short, they still exceed the minimum suggested record length of 10 years (U.S. Geological Survey, 2019) and produce recurrence intervals with adequate confidence. Data through WY 2022 were included in the analyses. The USGS streamgage on McLeod Creek (10133600) was established in 1991 and had a 7-year hiatus in monitoring between 1997 and 2002; all available complete WYs are incorporated into the analysis. Annual peak discharge has typically occurred in the late spring or early summer during the period of record. Kenney and others (2007) provided additional work on flood frequency for streams and rivers in Utah including East Canyon Creek.

Annual exceedance probability indicates the probability that measured streamflow will be equaled or exceeded in a given year, whereas a flood recurrence interval is the number of years before a flood of a given magnitude is statistically likely to recur. The AEP is used in this study. The flood recurrence interval (for example, a 100-year flood) has become a less commonly used indicator of flood frequency because it can be misleading with respect to the imminence or absence of flooding.

Baseflow Estimation by Conductivity Mass Balance Hydrograph Separation

Baseflow was estimated at three USGS streamgages (10133650, 10133800, and 10133980) on East Canyon Creek. Daily baseflow (fig. 5), mean daily baseflow (fig. 6), and annual and seasonal BFI (table 3) were calculated by conductivity mass balance hydrograph separation and associated calculations at each streamgage. The annual streamflow and baseflow volume delivered to East Canyon Reservoir at USGS streamgage 10133980 ranged from approximately 16,800 to 92,000 and 11,000 to 60,000 acre-feet (acre-ft), respectively. These values were based on the annual mean discharge at the streamgage according to annual statistics for the period of record (U.S. Geological Survey, 2024). Though streamflow and baseflow proportionally increased at streamgages downstream as East Canyon Creek gains from its tributaries, the contribution from baseflow to streamflow decreased by about 10 percent (table 3). The streamflow and baseflow volumes increased by a factor of approximately 3 from the most upstream USGS streamgage (10133650) to the most downstream USGS streamgage (10133980).

The annual BFI ranged between 0.592 and 0.697, and all sites demonstrated a consistent response to seasonal change in hydrology over the course of the water year. At the beginning of the water year (October 1), baseflow was the dominant component of streamflow through the winter (BFI=0.751–0.835; table 3). Streamflow and baseflow values then increased in parallel during spring runoff (BFI=0.712–0.814; table 3) until late spring–summer when baseflow values declined as runoff values continued to increase. While streamflow declined throughout the summer, baseflow decreased in parallel through the remainder of the water year (BFI=0.428–0.532; table 3). The annual variance, measured by standard deviation, of baseflow estimates ranged from 15 to 18 percent (table 3).

The mean daily streamflow and baseflow on East Canyon Creek represented the general relation between streamflow components throughout the water year (fig. 6). Though the actual mean daily streamflows or baseflows were dependent on annual snowpack and were highly variable in magnitude year-to-year (fig. 5), the relation (or BFI) between streamflow and baseflow largely remained constant during the winter but was more susceptible to fluctuation during the summer (fig. 7).

The effect of effluent on baseflow at the two downstream sites was not assessed by statistical means, though its cumulative impact was qualitatively determined to be minimal at annual timescales. However, low flows during the summer months may incorrectly underestimate the daily baseflow component of streamflow at the USGS streamgage upstream from East Canyon Reservoir (10133980). Because the daily SC of effluent was estimated by linear interpolation of a monthly value, which also was converted from TDS, the suitability of estimating daily SC decreases when the streamflow is nearly equal to the effluent discharge. These circumstances resulted in underestimating the BFI, down to nearly zero, on low flow days (fig. 7).

Trends in Annual and Seasonal Streamflow, Baseflow, and Climatological Data

The Mann–Kendall test for trends was done at annual timesteps for USGS streamgages and SNOTEL sites. Statistically significant trends on annual timesteps were not detected from streamgage or SNOTEL data (fig. 8). At the annual scale, the records were likely too short to develop statistically significant trends. Probability is represented by p-value and can be used to initially test for assessing statistical significance. A level of significance of 0.05 (α=0.05) was used to determine statistical significance for trend results; Mann-Kendall test results indicate that statistically significant annual trends were not detected. Corrections for autocorrelation did not appreciably change the results of the annual trend tests. Tabular test results are available at https://doi.org/10.5066/P14SJDMX (Root, 2025).

Monthly trend tests or Seasonal–Regional Kendall tests identified statistically significant trends, particularly with respect to streamflow and baseflow. Monthly mean streamflows and baseflows at USGS streamgages 10133650 (uncorrected p-values of 7.08E−4 and 2.71E−6, respectively) and 10133980 (uncorrected p-values of 0.011 and 0.015, respectively) had decreasing trends over the period of record (WYs 2011–22). U.S. Geological Survey streamgage 10133800 showed less likelihood of a trend in monthly mean streamflow and baseflow, with uncorrected p-values of 0.046 and 0.138, respectively. Monthly mean temperature at SNOTEL station 814 indicated a positive trend and was the only climate variable with a statistically significant trend (uncorrected p-value of 0.024). When SNOTEL attributes were tested with streamgage data as response covariables, only seven instances, including maximum precipitation recorded during each month at SNOTEL station 814 with baseflow as the response covariables at USGS streamgage 10133650 (fig. 9), indicated significant trends may be present. Only two of these instances had corrected p-values below 0.05: (1) mean temperature at SNOTEL station 814 with a response covariable of BFI at USGS streamgage 10133800 (corrected partial p-value of 0.049) and (2) total number of days in a month where SWE loss is recorded at SNOTEL station 684 with a response covariable of streamflow at USGS streamgage 10133650 (corrected partial p-value of 0.050). Other combinations of covariable pairs included streamgage-to-streamgage or streamgage-to-SNOTEL data (where SNOTEL data were the response covariable) that are intrinsically autocorrelated; these results were expected to produce the most statistically significant trends, thereby demonstrating the resiliency of the trend test. For example, monthly streamflow at USGS streamgage 10133650 tested for trend with a response covariable of streamflow at USGS streamgage 10133800 that resulted in an uncorrected partial p-value of 1.85E−4.

Correlations in Annual and Seasonal Streamflow, Baseflow, and Climatological Data

The Kendall’s tau test for correlation yielded results that indicated strong correlations between streamgage and climatological SNOTEL data were present at annual and monthly timesteps. Tabular results of the correlation tests were summarized in a data release at https://doi.org/10.5066/P14SJDMX (Root, 2025).

The strongest correlation was between annual streamflow at USGS streamgage 10133650 and annual peak SWE at SNOTEL station 814. This pair was the only test for annual data that indicated a strong linear correlation by Kendall’s tau (0.709), though there was strong evidence (p-values between 0.002 and 0.017) with a high probability of correlation for streamflow and baseflow at all streamgages with peak SWE and cumulative precipitation at SNOTEL station 814. These test statistics were used as a guide for correlations that may be statistically significant and do not substantiate a definite relation.

Correlation test results at monthly timesteps highlighted many statistically significant correlations between streamgage and climatological SNOTEL data. Among the strongest correlations were spring streamflow and baseflow with winter precipitation and SWE (fig. 10). This correlation was strongest between streamflow and baseflow at downstream USGS streamgages 10133800 and 10133980; USGS streamgage 10133650 had a comparatively weaker correlation between streamflow and baseflow in the late spring months (April–May) with maximum monthly precipitation and SWE at SNOTEL station 814 in the winter (January–March). Because all streamgage and SNOTEL attributes were tested against one another every month, some results indicated a false correlation between intrinsically unrelated measures such as spring streamflow and summer precipitation.

Flood Frequency

Table 4 summarizes estimates of flood frequency on East Canyon Creek. The results provide flood frequency data in terms of AEP and recurrence interval for East Canyon Creek and McLeod Creek above East Canyon Reservoir.

The highest annual peak streamflow in the period of record at all streamgages (figs. 4, 11) was 876 ft³/s, recorded on April 18, 2011, at USGS streamgage 10133980 (U.S. Geological Survey, 2024). This peak streamflow indicated a flood with an AEP of approximately 6.2 percent. Because this peak streamflow represented the upper end of recorded streamflows, the upper and lower confidence limits widened without additional data. For this event, the AEP may have been as high or low as approximately 11 or 0.4 percent, respectively. Further upstream on East Canyon Creek or McLeod Creek, the range of possible peak streamflows with low AEP narrowed.

Baseflow Estimation

The spatial distributions of streamflow and baseflow volumes varied downstream, whereas the drainage areas increased and East Canyon Creek gained flow from its tributaries. The median annual streamflow volume and annual baseflow volume at each streamgage did not linearly increase downstream. The streamflow volume (table 5) that entered East Canyon Reservoir (10133980) was approximately 28 percent greater than the streamflow volume below ECWRF (10133800) despite the drainage area nearly doubling from 57.2 to 107 mi². This relation is not strongly affected by year-to-year fluctuations in snowpack or precipitation because the ratio of annual streamflow and baseflow volume delivered to East Canyon Reservoir does not appreciably change with magnitude (table 5). However, patterns in baseflow at the lowermost USGS streamgage above East Canyon Reservoir (10133980) were often inconsistent with patterns in baseflow at the upper two USGS streamgages (10133650 and 10133800) during the summer months, particularly with respect to a decrease in BFI (fig. 7). This decrease was often associated with low flows.

Although the annual effluent contribution from ECWRF is a small fraction of total streamflow volume in East Canyon Creek, it may be a substantial component of streamflow during seasonal periods with low flow. Baseflow estimation would be unquantifiable without accounting for effluent by mass balance during seasonal low-flow periods while streamflow decreases during the winter. The path of East Canyon Creek between the uppermost USGS streamgage (10133650) and East Canyon Reservoir does not pass through urban sources of contaminants, although this stretch has historically been used for ranching and subjected to water diversions (Brooks and others, 1998; Wilkowske, 2005). One such pumped diversion includes the Glenwild Golf Club (not shown on figures) which is north of East Canyon Creek between USGS streamgages 10133650 and 10133800. There is a housing development in the Jeremy Ranch community (not shown on figures) and a second golf course, Jeremy Ranch Golf and Country Club (not shown on figures), that East Canyon Creek runs through, though the contribution to salinity from irrigation on the golf course is not known. The primary source for contaminants likely remains I-80, where East Canyon Creek runs parallel to I-80 between USGS streamgages 10133650 and 10133800. Below Jeremy Ranch, much of these lands have been used for ranching dating back to the 19th century (Halverson, 2012), and no significant agricultural districts on East Canyon Creek are noted before reaching the USGS streamgage above East Canyon Reservoir.

The drainage areas represented by USGS streamgages that measure continuous SC on East Canyon Creek increase downstream from 42.1 (10133650) to 57.2 (10133800) to 107 mi² (10133980). Streamflow and baseflow volume do not linearly increase in proportion from one streamgage to the next. The most upstream USGS streamgage in the reach (10133650) represents approximately 39.3 percent of the drainage area of the most downstream USGS streamgage above East Canyon Reservoir (10133980); streamflow and baseflow volumes at the USGS streamgage below I-80 (10133650) account for 39.3 and 41.8 percent, respectively, of the total volume above East Canyon Reservoir (10133980). Approximately 53.5 percent of the total drainage area is represented by the USGS streamgage below the ECWRF (10133800) but accounts for 71.8 and 64.9 percent of streamflow volume and baseflow volume at East Canyon Reservoir (10133980), respectively. The error bounds for baseflow allow for this disparity to decrease, although streamflow is a measured value and does not have the same level of uncertainty. East Canyon Creek flows out of the greater Jeremy Ranch region and enters a more constricted canyon with numerous tributaries that directly drain off adjacent slopes. This may indicate less surface water runoff is delivered to East Canyon Creek in the section between the lower two USGS streamgages (10133800 and 10133980) or a significant volume of streamflow in East Canyon Creek is diverted.

Seepage studies were done on East Canyon Creek between USGS streamgages 10133650 and 10133800 between 1983 and 2004. The first was done in a year with greater-than-average precipitation and found this reach of East Canyon Creek had a seepage gain of 2.7 ft³/s or 19 percent (Holmes and others, 1986). A second study (Brooks and others, 1998) reported a seepage loss through Kimball Junction using measurements between 1994 and 1995 (Downhour and Brooks, 1996). The third study found this section of East Canyon Creek is a slightly losing reach, with total seepage losses ranging from −1.9 to 0.3 ft³/s or 8 to −27 percent of streamflow at USGS streamgage 10133650 (Wilkowske, 2005). Using data from the full period of record at SNOTEL station 684 (1979–2023), the median annual peak SWE was 450.1 inches (in.). Water years 1983, 1994, 1995, and 2004 had peak SWE values of 690.9, 332.7, 370.8, and 414.0 in., respectively. The seepage rates for each study, and whether East Canyon Creek was gaining or losing in the respective reaches, coincided with the snowpack for the respective year. Streamflow and estimated baseflow during WYs 2011–22 did exhibit a strong positive correlation with snowpack and precipitation over the period of record.

The BFI of East Canyon Creek indicates a baseflow-dominated hydrology, with upwards of 80 percent of total streamflow attributed to baseflow during the fall, winter, and spring (table 3); this characteristic is not regionally exclusive to East Canyon Creek and has been observed elsewhere in the Wasatch Mountains and nearby ranges (Rumsey and others, 2015). Trends in BFI were among the tested measures with the weakest statistical significance at annual or seasonal timescales, and those results may indicate the period of record was too short to characterize a trend if present. Because other streamgages on the eastern slopes of the Wasatch Mountains (which are partially located in the Upper Colorado River Basin) also indicate comparable BFI (0.55–0.92), the results from this study may further corroborate a regional hydrological characteristic (Rumsey and others, 2015). Overall, this study demonstrates that baseflow is a critical component of the regional hydrology on East Canyon Creek, and groundwater discharge represents a significant fraction of the total streamflow in the basin. The estimates of baseflow corroborate previous findings that higher elevation watersheds with greater total precipitation, steeper slopes, resilient snowpack, and sandy soils promote a greater baseflow component (Rumsey and others, 2015).

Trends and Correlations in Streamflow, Baseflow, and Climatological Data

Seasonal-trend testing indicated that streamflow and baseflow on East Canyon Creek above East Canyon Reservoir have declined over the period of record, with changes in snowpack likely having a prominent role in this change. The annual peak SWE for the years in which baseflow was estimated (WYs 2011–22) was below average in 9 of 12 years at SNOTEL stations 684 and 814. The first year in the study period (WY 2011) had the highest peak SWE; the remaining record and any detected trends may thus be skewed negatively in response. The poor distribution of data likely limits the effectiveness of the Mann–Kendall test for trends using annual data, which were inconclusive for all measures. A longer and more representative sample population of climate data, more so than streamflow, are necessary for more substantiated trend analysis. Similar trend studies that incorporate a longer record from SNOTEL stations provide meaningful insight into a changing climate in the Wasatch Mountains (Hu and Nolin, 2020; Hale and others, 2023). Most relevant to East Canyon Creek, earlier melting in the Great Salt Lake basin (Hall and others, 2021) and lower ratios of SWE to winter precipitation are linked to significantly lower maximum SWE in the Wasatch Mountains during the period from 1984 to 2009 (Harpold and others, 2012) as streamflows and baseflows during the spring may negatively correlate with the number of days that record a loss in SWE in the same or preceding month at the Thaynes Canyon SNOTEL station 814 (fig. 12; Root, 2025). In these examples, the relations between streamflow or baseflow and the number of days with recorded loss of SWE in April at SNOTEL station 814 are not well defined. The Kendall’s tau (all below 0.7) and p-values (0.027–0.097) are in opposition regarding the significance of correlation. Earlier declines in streamflow may lead to a less resilient baseflow contribution during the summer (fig. 7) and increased reliance on runoff below ECWRF to sustain East Canyon Creek and, ultimately, East Canyon Reservoir.

At seasonal timescales, changing climatic conditions in the Wasatch Mountains directly affect its tributaries including East Canyon Creek. This study aimed to characterize relations between streamflow and climate using robust statistical assessment limited to the period of record for baseflow estimation on East Canyon Creek. This timeframe (WYs 2011–22) constrains the long-term potential for trends in climatological data from SNOTEL stations and limits the strength of its results. Trends for all measures of climate, including precipitation and temperature, are inconclusive as single variable tests or in the presence of a covariable; however, the results here do not exclude possible trends in SNOTEL data for their full respective periods of record.

Predictive Models for Streamflow and Baseflow Using SNOTEL Data

Correlations of streamflow and baseflow with SNOTEL climatological data could be used to predict hydrological conditions. Though statistically significant trends are not well observed in this study, at least in part because of the length of instrumental record, strongly correlated pairs of streamflow or baseflow and SNOTEL data (particularly at monthly timesteps) provide a statistical framework that could support the development of flow forecasts on East Canyon Creek. Among the strongest correlations are those for winter snowpack and spring streamflow or baseflow (fig. 10). Results from the correlation tests provide all required inputs to build a regression using SNOTEL data to determine streamflow, baseflow, or BFI.

The Theil–Sen line slope and y-intercept are used to construct regressions for streamflow or SNOTEL conditions:

Using monthly data and Theil–Sen line results from the supplemental data release of this study as an example (fig. 13; Root, 2025), the January maximum SWE at the Parleys Summit SNOTEL station (684) strongly correlates (Kendall’s tau=0.901; p-value=6.70E−05) with the May baseflow at the streamgage nearest the ECWRF (USGS streamgage 10133800). The Theil–Sen line (for the pair mentioned above) has a slope of 0.145 with lower and upper 95-percent confidence interval slopes of 0.073 and 0.277, respectively, and a y-intercept of −15.9. The slope and intercept estimate of the Theil–Sen line may be used to predict streamflow given a SNOTEL variable. The median maximum SWE in January during WYs 2011–22 is 254 millimeters (mm); using this value in the equation above, the mean monthly baseflow for May at USGS streamgage 10133800 is estimated as 20.9 ft³/s with lower and upper 95-percent confidence interval bounds of 2.63 ft³/s and 54.5 ft³/s, respectively.