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<br />,1J~:? . ,) 7 <br />J _,.J <br /> <br />evaluate the sensitivity of color and color-infrared phorographs to changes <br />in turbidity and further to determine if turbidity could be indirectly <br />measured (quantitatively) using the photographs. If a correlation between <br />reflectance and turbidity does exist, then only a few selected ground- <br />sampling points should be required to calibrate the reflectance levels <br />appearing on the aerial photographs with measured turbidity values. <br /> <br />This investigation was planned so that the aerial photographs and the <br />ground information would be acquired during the period of peak snowmelt <br />runoff, in order to insure a wide range of turbidity values. Approximately <br />30 ground-sampling sites initially were selected in mid-May for collection of <br />turbidity and suspended-sediment samples to coincide with rhe acquisition of <br />aerial photographs. <br /> <br />However, due to scheduling conflicts and limited manpower, turbidity and <br />suspended-sediment samples were collected at only eight stations on rhree <br />streams at approximately the same time as the overflight during which the <br />color and color-infrared photographs were acquired. Sampl ing-station <br />locations are depicted on figure 17. Individual sampling stations and the <br />turbidity and suspended-sediment values obtained during the ground sampiing <br />are presented in table 5. <br /> <br />Tab I e 5. --Turbidity and suspended-sediment measw'emerlts obtained <br />May 31 and June 1, 1977 <br /> <br /> Turbidity, Suspended-sediment <br /> Date S i tel in Formazin concentration, <br /> turbidity units in milligrams per liter <br /> 1977 <br />May 31------ Y-47 4 29 <br />May 31------ Y-64 4 16 <br />May 31------ Y-71 3 68 <br />June 1------ Y-OA 8 34 <br />June 1------ Y-l 48 402 <br />June 1------ y-17 9 51 <br />June 1---- -- Y-39 4 42 <br />June 1------ Y-40 II 23 <br /> lSee figure 17. <br /> <br />Positive-color and color-infrared transparencies were <br />ison of spectral reflectance and measured turbidity values. <br />television camera associated with the Image-100 System <br />digitize the parts of the transparencies depicting the <br /> <br />used for compar- <br />The aux i 1 i ary <br />was employed to <br />segments of the <br /> <br />35 <br />