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<br />lG'j 1 <br /> <br />The EPA's most recent water quality criteria (EPA, 1976) recommend <br />that fecal coliforms be used as the standard for evaluating the sanitary <br />quality of water. The State's proposed drllft, standards would follow <br />this recommendation and drop the current standards for total coliforms <br />and fecal streptococci. On the basis of the draft standards, the <br />reservoir could be classified as being suitable for primary contact <br />recreation. <br /> <br />Temperature Simulation <br /> <br />Using the Corps of Engineers (1973) modification of the Water Resources <br />Engineers (WRE) Reservoir Temperature Simulation Model, the temperature <br />regime of the' reservoir was simulated. The simulation was run for <br />three years, comprising 1963, 1965, and 1967; these represent a "dry," <br />a "wet," and a typical year respectively on the basis of total annual <br />runoff. Input data were drawn from the National Weather Service <br />Climatological Data Record, the Geological Survey stream gaging <br />network, and the Bureau's Operations Study for the Narrows Unit. The <br />streamflow data were taken from the records at the Weldona gaging <br />station, while the daily inflow temperatures for the Julesburg <br />Irrigation Network Station were used. The Julesburg data were used <br />only after a statistical comparison with all available data for the <br />Weldona station verified the validity of superimposing them upstream. <br /> <br />The results of the simulation indicate that the reservoir will usually <br />follow the classic spring pattern of surface warming and have a period <br />of the establ ishment and disruption of near-surface, unstable strati- <br />fication. This period would last for one to two months. <br /> <br />'J <br /> <br />The duration of stratification and the ma~imum summer temperature were <br />ultimately dependent on the size of the reservoir pool at initial <br />sprin9 warming. Although 1965 was a "wet" year on the basis of runoff, <br />prior to the onset of the spring runoff, the reservoir was at its <br />lowest level of the three years, i.e. approximately 14 meters deep. <br />Under this condition, the above described pattern occurred during the <br />spring. This was followed by a rapid warming to the bottom and no <br />development of persistent stratification. During June, extreme <br />inflow raised the pool level by six meters. However, no ~lell- <br />defined stratification developed, and the reservoir continued warming <br />throughout the summer. The bottom temperature was in excess of 200 C <br />for a peri od of 60 consecu ti ve days. <br /> <br />19 <br />