City Creek Nature Notes – Salt Lake City

June 13, 2017

June 4th

End of the Snowmelt

7:00 p.m. Temperatures reach 97 degrees today; one degree short of a record. As a consequence, the SNOTEL station at Louis Meadows records that all of the snowpack at near mile 7.0 of the canyon is gone. This is a seasonal milestone, and from now to next October 1st, the stream will flow only from rainfall and water stored underground. This afternoon, clouds stream in from the west, but it is too hot for the rain, which falls in curtains from a thousand feet overhead, to reach the ground.

Birds are quiet in this later evening, but still a single Blacked-head grosbeak is seen and heard near mile 0.2. A single House sparrow and a Chirping sparrow are also heard along the first mile road. Later, returning down canyon, I am for the first time able to see and hear the grosbeak performing a call with three low notes followed by a trill. This is a common call heard in the first canyon mile, but it does not appear in my reference recordings for this grosbeak. Other songs and calls for this grosbeak are in the reference recording. Butterflies are also subdued in the evening. There are single instances of a Mourning cloak, a Cabbage white and a Western tiger swallowtail. Gnats are rising in the heat.

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In Thoreau’s “Journal” on June 4th, 1852, he hears birds singing at dawn and he sees that dandelions have gone to seed. On June 4th, 1853, crickets are singing at noon. He examines oak and chokeberry leaves. On June 4th, 1855, white and red clover are blossoming, and mosquitoes are rising. On June 4th, 1857, he notes “earth-song,” or the combination of the sounds of insects and birds as a sign of summer. On June 4th, 1860, he notes elm trees are in full foliage, and that warblers have left for the season. Buttercups are in bloom. He sees a cat bird.

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How much water is stored in the east and west halves of the Salt Lake salient (may 14th) that drain into the stream? Using the difference between stream flow data taken at the canyon’s water treatment plant from 1950 to the present and precipitation records from the Louis Meadow SNOTEL station for 2000 to the present, I am able to make a rough estimate of the lower bound of stream flow that comes solely from underground reservoirs. For two months each year – June and July, average stream flow exceeds average precipitation. In June, the average stream flow exceeds rainfall by about 318 acre feet, and in July, the stream flow exceeds rain by about 242 acre feet, for a mean underground flow into the stream of 280 acre feet per month. This 280 acre feet per month is the lower bound. Summer rainfall will evaporate and never reach the stream or recharge underground aquifers. Depending on underground geologic structures, all of the water that falls within the 19.2 square miles of the canyon may not flow towards the stream. The oak and fir forests and grasses consume considerable quantities of rain water, and those withdrawals are not included in the sum of the difference between inflows and outflows. Thus, the true amount flowing into the stream from underground aquifers could be two or three times the lower bound of 280 acre feet per month. The 280 acre feet of water each month is enough to flood 28 of the city’s 10 acres blocks with a foot of water. The volume of that water is about 12.2 million cubic feet of water (0.000083 cubic miles), or a cube about 230 feet on a side. In contrast, the Mormon Temple that sits at the heart of City Creek Canyon’s delta (March 10th and March 12th) is 288 feet tall.

The lower bound of 280 acre feet of underground storage is a reasonable estimate. Treating the 12 miles of the Salt Lake Salient as two inward facing right-triangles that are 1.25 miles from the stream to ridgeline, the volume of the salient that drains towards the stream is about 32.5 cubic miles. The 0.000083 cubic miles of underground water flow is only 9 of 10,000,000ths of the salient’s volume. That water can easily fit in the pores space between the salient’s rocks.

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On June 4th, 1934, University of Utah Engineering Professor F. W. Muir reported that tree rings taken from City Creek Canyon and near Brighton show that in the last 300 years, there have been many drought cycles (Salt Lake Telegram). On June 4th, 1914, the City acquired 80 acres of private land in City Creek (Salt Lake Telegram). On June 4th, 1910, Land and Water Commissioner Frank Mathews reported that green caterpillars, possibly one million, are moving down City Creek Canyon defoliating (“stripping bare”) the trees (Salt Lake Telegram). On June 4th, 1906, streets in Salt Lake City principally from 300 West to 800 West, were severely flooded (Salt Lake Telegram).

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