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<br />..&:>. <br />o <br />CJl <br />0'0 <br /> <br />Mead by Anderson and Pritchard [6J and <br />Harbeck et al. [4J using monthly data <br />from October 1977 - September 1978 <br />k. unit conversion factors <br />1 <br /> <br />Total evaporative water loss from Lake Mead was then <br />determined by extrapolation from volume curves [8], <br />Using USGS data collected during the period from Octo- <br />ber 1977-September 1978 as initial model conditions (Table <br />I), the effects of decreased evaporation on salinity in Lake <br />Mead were determined by Equation 3. <br /> <br />SCt = <br />where Sc <br /> Ss <br /> Si <br /> a <br /> So <br /> V <br /> Ev <br /> t <br /> k. <br /> 1 <br />Table 1. <br /> <br />SSt_l + (Sita - SOt) <br />V t + Ev t <br /> <br />k ---k <br />i n <br /> <br />(3) <br /> <br /> sal t concentration in Lake Mead (mg!l) <br /> salt storage in Lake Mead (kg) <br /> salt inputs to Lake Mead (kg) <br />= salt retention coefficient <br />= salt output at Hoover Dam (kg) <br />= Lake Mead volume (m3) <br /> evaporation reductions (m3) <br /> time interval (yr) <br /> unit conversion factors <br /> <br />Parameters and Data Used in the Salinity Model for <br />Lake Mead. Data Collected Oct. 1977 - Sept. 1978. <br /> <br />Parameter Symbol Average Units <br />Lake Mead Volume V 25.48 m3 x 109 <br />Colorado River Inflow I 10.43 m3 x 109 <br />Hoover Dam Discharge 0 9.48 m3 x 109 <br />Salt Input Si 73.714 kg x 10B <br />Salt Retention a 0.8693 <br />Salt Storage Ss 172.76 kg x 10B <br />Salt Output So Variable kg x 10B <br />Evaporation Ev <br />Red uc tion IUnimum 1.48 mg x 10B <br /> 1'-laximum 2.63 m3 x 10B <br /> <br />Evaporation reductions of 120,000 acre-feet (1,48 x <br />10Bm3) and 213,000 acre-feet (2.63 x 108m3) ;rere used in the <br />salini ty model. These evaporation reductions were added to <br />the 1978 ;rater year average vollli~e in Lake Mead (25.48 x <br />109m3) during the first year of modeling. In subsequent <br />years, these evaporation reductions ;rere added to the annual <br />discharges from Hoover Dam, using the 1978 water year (9.48 <br /> <br />5 <br />