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32 <br />thus the data can be compared to other areas in North America where • <br />erosion research has been done. <br />The plots were seeded and mulched on October 1, 1975. The seed- <br />bed was prepared by raking to loosen the soil and then the seed was <br />hand broadcast; a very light raking was used to cover the seed. The <br />alfalfa mulch '.vas spread by hand and a cotton netting was used to hold <br />it down. <br />11 ft. x 22 ft. Plots <br />In our work with vegetative stabilization of spent oil shales <br />at Anvil Points and the Piceance Basin near Rifle, Colorado, we have <br />Pstablished fifty-six 11 ft. x 22 ft. plots on a 4:1 slope. The <br />purpose of that same size plot on the same slope at the Colowyo site <br />is to compare runoff and sediment yield for the different climatic <br />regimes, vegetative covers, and soil conditions of northwestern <br />Colorado. <br />Only two treatments were used in this study. The two treatments <br />were selected as the extremes in management practices. The two <br />treatments are: <br />1. Shrubs seeded only (2 replications) <br />2. Shrubs, grasses, and fortis seeded - mulched <br />and fertilized (2 replications) <br />The seeding rates and the cultural practices are the same as <br />the larger runoff plots. The treatments are listed to the right of <br />each plot (figure 9). The plots were seeded and mulched October 1, 1975; <br />and the procedures for seeding and mulching are the same as those use <br />on the 11 ft. x 73 ft. plots. <br />Runoff and Sediment Yield Measurements <br />• <br />Measurements of runoff and sediment yield were made during the <br />spring snowmelt and after each intense sumr~er storm. Spring runoff, <br />Table 10, consists of all snowmelt and rain from November 1975 through <br />June 2, 1976: the amount of precipitation that fell during the period <br />was approximatley 184 mm. Table 10 also includes runoff and.sediment <br />yield data for the storm period ending on June 24. The runoff for this i <br />storm period is primarily from a thunderstorm on June 23; 11.5 mrn of _ <br />precipitation fell in this storm. Between June 2 and June 23, there <br />was an additional 6 mm of precipitation; this additional moisture also <br />contributed to the runoff and sediment yields in Table 10. The runoff <br />on June 24 was the last major runoff event of the summer. Light <br />thunderstorms did occur throughout the summer but increases in the <br />• <br />