Big Blue River rises at about 1,800 feet above mean sea level and joins the Kansas River at an elevation of 1,000 feet above m. s. l. The average gradient is 2.8 feet per mile. Little Blue River, originating at 2,200 feet, has an average gradient of 5.3 feet per mile, entering the Big Blue at 1,100 feet above mean sea level (Nebraska State Planning Board, 1936:628, 637). The Little Blue is the shallower stream, possibly because of the greater amount of sandy glacial deposits in its watershed and the swift flow that may cause lateral cutting, increased movement, and "drifting" of the sandy bottom. For approximately a 50-year period, stream-flow in the Big Blue River at its point of entry into Kansas (Barnston, Nebraska) averaged 603 cubic feet per second, with maximum and minimum instantaneous flows of 57,700 c. f. s. and one c. f. s. The Little Blue River at Waterville, Kansas, averaged a daily discharge of 601 c. f. s. (maximum 50,400, minimum 28). Below the confluence of the Big Blue and Little Blue rivers, at Randolph, Kansas, the average daily discharge was 1,690 c.f.s. (maximum 98,000, minimum 31) (Kansas Water Resources Fact-finding and Research Committee, 1955:27). The turbidity of the Big Blue River, as determined by use of a Jackson turbidimeter, varied from 27 parts per million in winter (January 10, 1958) to as high as 14,000 p.p.m. (July 12, 1958). The Little Blue River has similar turbidities, with high readings being frequent. In the summer of 1957, pH ranged from 7.2 to 8.4 in the Big Blue River Basin--values that correspond closely with those of Canfield and Wiebe (1931:3) who made 25 determinations ranging from 7.3 to 8.3 in the streams of the Nebraskan portion of this basin in July, 1930. Surface temperatures at various stations varied from 38 deg. F. on January 10, 1958, to 90 deg. F. in backwater-areas on July 19, 1957. The average surface temperature at mid-day in July and August, 1957, was approximately 86.5 deg. F. Chemical determinations were made on water-samples from my Station 4-S on the Big Blue River, and Station 50-S on the Little Blue (Table 1). These samples were taken from the surface in strong current. Determinations were made by methods described in _Standard Methods for the Examination of Water and Sewage_, 10th edition, 1955. TABLE 1.--CHEMICAL DETERMINATIONS IN MILLIGRAMS PER LITER AT FIVE STATIONS IN THE BIG BLUE RIVER BASIN, KANSAS, 1958. TABLE LEGEND: Column A: Phenolphthalein alkalinity Column B: Methyl-orange alkalinity Column C: Chlorides Column D: Sulphates Column E: Nitrates Column F: Nitrites Column G: Ammonia Column H: Phosphate