Laserfiche WebLink
<br />I- <br /> <br />i <br /> <br />I' <br />I <br /> <br />is either grass or grass mixed with yucca bushes. Two rainfall-simulation <br />plots were established in the upper watershed; three plots were established <br />in the lower watershed (fig. 1). Boundaries of lawn edging were installed <br />around each plot. Size of the plots ranged from 2,099 to 2,720 ft2. All <br />plots were equipped with I-in throat Parshall flumes, and digital recorders <br />with a 5-min punch interval. A pressure transducer was installed in each <br />flume and connected to a data logger that records stage at I-min intervals, <br />and activates a pumping sampler, at predetermined stage, for determination <br />of sediment load. Data loggers also record rainfall at I-min intervals, <br />from O.Ol-in tipping-bucket rain gages, located near plots 1-2 and near <br />plots 3-5. <br /> <br />Several well-defined drainage basins exist within the watershed. Meas- <br />uring sites were established on four of these tributaries (fig. 1):' Super- <br />critical 3-ft concrete flumes were constructed at the South Fork (303 acres) <br />and North Fork (149 acres); Parshall flumes with 4-ft throats were installed <br />at the West Fork (61 acres), and East Fork (53 acres). All flumes were <br />equipped with digital recorders with 5-min punch intervals. The previously <br />operated gaging station at the mouth of the basin is on the natural channel, <br />which was rated by the step-backwater method and slope-area measurements. <br />Dual digital punch recorders with 5-min interval measured rainfall and water <br />stage at this location from 1970 to 1979 and 1981, 1982. <br /> <br />Development of Runoff Data from Rainfall Simulator <br /> <br />During 1981 and 1982, a total of 23 rainfall-simulation runs lasting <br />from 30 to 60 min were made on the study plots (fig. 4). In July and August <br /> <br /> <br />Figure 4.--Rainfall simulator in operation, <br />plot 2, Willow Gulch study watershed. <br /> <br />7 <br />