A water year in USGS hydrology records ends on Sept. 30, when rivers drop to their baseline flow. Here’s a summary of water year 2023 on the White River. It ran higher longer than in 2022. Good news in that regard. Overall climate trends in the basin, however, remain alarming.
Following are summary data tracking climate and river discharge in the White River Basin. You can find the full data sets in the USGS and Snotel data summaries. (See link at the end of this article.) Climate data come from the snotels at Trappers Lake, Burro Mountain, and Ripple Creek, each with records spanning water years 1987 to present. Flow data comes from the USGS continuous real-time gauging station near Meeker (station 09304500) which has the longest continuous record along the White River, from 1910 through present.
Here, in brief, are salient results:
Total precipitation at the headwaters, mostly snowpack, hit records in 2023. As a consequence, mean daily runoff exceeded the historical median flow from April through July. It hovered around the historical median the rest of the year.
Mean daily temperatures on the Flat Tops in recent years are significantly higher than when data collection began 37 years ago (Figures 1 and 2). These observations are consistent with larger climate studies. Other data (not shown) document rising average daily mean temperatures at all three snotels in each successive five-year interval since 1987. The greatest increases in temperature occur in mid-winter and late summer.
Precipitation on the Flat Tops is decreasing (Figure 3). There is less water available for runoff into the headwaters of the White River. These trends have become more pronounced in recent years.
Total yearly runoff in the White River is decreasing (Figure 4), down by about 65,000 acre feet average over the period of record. That represents roughly a 14% loss in available water volume. Downward trend is particularly evident in late summer as the river returns to base flow (Figure 5).
Peak flow is decreasing, now roughly 500 cfs lower on average than it was in 1910. Peak runoff also occurs earlier in the Spring. (Data available online. See link in References.) Among other consequences, low peak flow scours algae off the stream bed less effectively. Decreased flow also changes sediment transport and fish habitat along the river. Longer periods of low flow in the summer provide favorable conditions for algae growth, increase stress on fish, and decrease available irrigation and municipal water supplies.
The data presented here are consistent with global and regional trends toward a hotter, drier world. Updated climate models predict that climate conditions in the White River Basin 30 or 40 years from now will resemble the present brush and sandstone regime of southeastern Utah (Talsma et al, 2022; NCA 2023).
On a positive note: we haven’t seen a big algae bloom for the past couple years. It’s not clear what happened to stifle the algae. The final report from USGS on White River algae identified low water and higher water temperatures as probable contributing factors. Nutrients from fertilizers and septic systems also encourage algae growth. A brief bloom in mid-July this year faded rapidly. Its cause and rapid disappearance remain a mystery.
These data from the headwaters of the White River clearly show the signature of a changing climate. Temperatures are rising. Precipitation is decreasing. Discharge in the river is decreasing. The trends toward a hotter, drier climate persist. Extrapolating the trend lines, September flows may disappear early next century. Picture a dry riverbed, or maybe a trickle. Storage buffer in the Agency and Powell Park aquifers may extend time until worst case, and, as already evident around the world, we may experience wild fluctuations in weather, including floods. But people need to start planning. Best available evidence to date indicates that the White River is drying up.
Figure 1: Mean daily temperatures at Burro Mountain snotel, average of water years 1987-1991 (blue) vs. 2019-2023 (red). The most recent five-year average daily temperature is significantly greater than the 1987-97 average; t stat = 13.1, , paired t-test, n = 365. Plot is smoothed using a 10-day running mean. Mid-winter temperatures at Burro Mtn now average three to four degrees Centigrade (about 5.4 to 7.2 degrees Fahrenheit) warmer than thirty years ago. Summer temperatures are two to three degrees Centigrade (about 3.6 to 5.4 degrees Fahrenheit) warmer. Mean daily temperatures at Trappers and Ripple Creek snotels show similar trends.
Figure 2. Mean daily temperatures in January at Burro Mtn, 1986 – 2023. Upward trend is significant; Mann-Kendall S = 270, Z = 3.52, Zcritical = 1.96, n = 35. Trend line is best linear fit by least squares analysis. Trend line for August daily mean temperature is also increasing significantly. Ripple Creek and Trappers Lake show the same January and August temperature trends as at Burro Mtn, with similar statistically significant upward trends in daily temperature.
Figure 3. Cumulative yearly precipitation at Burro Mtn, water years 1986-2023. Trend is decreasing and significant. Mann-Kendall S = -221, Z = -2.32, Zcritical = -1.96, n = 35. Trappers Lake and Ripple Creek show similar trends and statistics.
Figure 4. Total runoff (acre feet) down the White River by year from 1910 to 2023. Trend is downward, trend line fit by least squares analysis. Mann-Kendall
Figure 5. Mean flow in the White River near the Town of Meeker in the month of September, water years 1950-2023. Mann-Kendall S = -2003, Z = -4.91, Zcritical = -1.96, n = 73. Trend line is best linear fit by least squares analysis.
References:
Fifth National Climate Assessment. 2023. National Academies of the United States. https://nca2018.globalchange.gov/
Talsma, Carl, Katrina Bennett and Velimir Vessilimov. 2022. Characterizing drought behavior in the Colorado River Basin using unsupervised machine learning. Earth and Space Science.
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2021EA002086
USGS and Snotel Data Summaries. 2023. http://dorsettedu.us/Climate/ClimateTrendsSummaryData_2022_PDF.pdf
BY BOB DORSETT, MD
