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Show HYDROGRAPHY. 25 No systematic data have been collected below the head of North Jordan canal, but in December, 1904, the following measurements were made by Mr. Caleb Tanner and the writer: Discharge of Jordan River and tributaries between Little Cottonwood Creek and the ford, in sec. 4, T. 1 N., R. 1 W., December C- 7, 1904. Second- feet. Jordan River above mouth of Little Cottonwood Creek 61.38 Little Cottonwood Creek - 8.14 Flume at Taylorville roller mill - 39.0 Big Cottonwood Creek i 51.2 Ditch south of Mill Creek ; 2.12 Mill Creek 23.94 Ditch, outlet of Decker Lake 2.93 Parleys Creek, north and south ditches 8.78 Eighth South street ditch -.. 6.09 Total 203.58 Jordan River below North Temple Street Bridge 190.22 190.22 Loss between mouth of Little Cottonwood Creek and North Temple street 13.36 Outlet of Hot Springs Lake 7.64 Sewer ditch ( estimate) : ". : 7.50 Jordan River at ford, sec. 4, T. 1 N., R. 1 W 214.00 Total .. 205.36 205.36 Gain between North Temple Street Bridge and ford 8.64 Loss in the flow of Jordan River, instead of expected gain, is thus shown between the mouth of Little Cottonwood Creek and North Temple Street Bridge at the time the measurements were made, while a slight gain is shown between the bridge and the ford in sec. 4, T. 1 N., R. 1 W. It appears t h a t the seepage drains into the tributaries rather t h a n directly into Jordan River in the area where the tributary streams are numerous and t h a t farther north, where there are fewer tributaries, a small amount of seepage drains directly into the river. How far these figures represent conditions the year round remains to be determined. GREAT SALT LAKE. Except during a lapse from 1893 to 1896, instrumental records of the surface fluctuation of Great Salt Lake have been kept since 1875, and there is evidence less exact dating back to the survey of the lake by Stansbury in 1849- 50. When that survey was made the level of the lake was extremely low, and since then it has varied considerably. In 1869 the water surface was approximately 11 feet higher than it was in 1850; a comparatively low stage was reached in 1873, after which the lake rose about 4 feet to a maximum in 1876, about equal to t h a t attained in 1869. In 1883 the lake was about 7 feet below the maximum; then it rose 4 feet until 1886, since when it has gradually fallen until now it is at an extremely low stage, about 15 feet lower than the maxima of 1869 and 1876. Fig. 4 illustrates the changes since 1875. Besides the irregular fluctuations there is a regular annual variation ranging between 1 and 2 feet, the maximum occurring in June and the minimum in the winter This annual variation is due to the changing relations of precipitation, inflow, and evaporation, high water occurring after the spring floods, and low water during the season of feeble stream discharge and after the period of excessive evaporation. The irregular variation of the past can be accounted for chiefly by changes in rainfall, the earlier maxima being associated with unusually large amounts of precipitation. The gradual decrease of late years in the volume of the lake, after allowing for recent dry seasons, is apparently due to largely increased irrigation, by which the inflow of surface streams has been checked |
