Summertime stream flow represents groundwater discharge, while the spring flows result primarily from snowmelt at higher elevations. Not all of the groundwater originating from upper elevation sources enters the stream before its leaves the canyon. Tracing the possible sources of water into stream, and therefore that water which is available to plants, is possible by analyzing the stable isotopic composition of that water. The hydrogen (d2H) and oxygengen (d18O) ratios of stream waters have been measured at the U.S.G.S. Benchmark station and at the mouth of Parleys Fork by the Stable Isotope Ratio Facility for Environmental Research at the University of Utah since June 1988.
These naturally occurring stable isotopes of hydrogen provide long-term data that are useful in addressing both long-term regional climatic patterns and the specific water sources used by plants for growth. Since 1988, hydrogen isotope ratios of stream waters have averaged near -122 ‰, with the only seasonal changes being more negative values occurring during spring snowmelt. Typically the hydrogen isotope ratio of winter storm events (snow) are more negative than that of summer storms. The hydrogen isotope ratios of wells and springs near Pinecrest (immediately east of Red Butte Canyon) are -132 ‰, which is slightly more negative than Red Butte Creek (Dawson and Ehleringer, 1991), and suggest that a fraction of the groundwater originating from the upper portions of the canyon may persist as underflow and does not enter the creek before leaving the watershed. Hely et al. (1971) indicated that substantial fracturing occurs in the bedrock of Red Butte Canyon, which would have the effect of increasing groundwater loss from the canyon through these layers and not via stream discharge.