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. . , \., 0762 water supply from the average existing supply of 65 percent to 95 percent, provided the ultimate plan is adopted as set forth in their report. The monthly reservoir operation study indicates that the reservoir would be empty about 5.7 percent of the time with water shortages occurring in 1934, 1935, 1936, 1937, 1939 and 1940. The longest period of consecutive monthly shortages occurred in 1940 for a 5-month period, June through October. The Bureau of Reclamation report on Trinidad Reservoir, and the reservoir oper'"tion studies for the period 1925-1949 are included in appendix D. 44. SediwG:1G sources. - The mountains are not an important source of sediment; but there are debris cones in the lower reaches of the tributaries and there is evidence of considerable lateral erosion. The entire stream sys'~e;n moves an appreciable bed load as evidenced by the wide, flat stream bed cOffiposed of sand and coarse material to cobble sizes. Degradation of the 'stream bed occurs during flood flows, but aggradation of the bed occurs during smaller flows. The steep slope of the river above Trinidad, lack of vegetative growth in the channel, and the abun- dance of bed material is also conducive to bed load movement. L6. Sediment sampling. - From 1940 to 1943, suspended sediment samples were obtained intermittently from the Purgatoire River at Trinidad, Colorado. Since 1943, sampling has been continued at the rate of about two samples per week at this station from 1 April to 30 September each year, and additional samples have been taken dl~ing flood stages. Only intermittent samples are obtained during the winter. Samples of bed load are not obtained; therefore, only a preliminary estimate of the bed load can be made. 46. Sediment volume at Trinidad. - Suspended sediment volume for the sampling period was computed by plotting the stream discharge from the recording gage; plotting the sampled sediment in percent by weight; 35 APPENDIX B .