three times as much runoff and sediment as 

 Watershed B. From 1924 to 1930 average 

 plant cover on both areas was about 40 per- 

 cent. Watershed A, though, continued to pro- 

 duce about twice as much runoff and erosion 

 as Watershed B, largely a result of a few bare 

 spots. Results of the first two decades of 

 study were published in 1931. (See Forsling 

 1931; Stewart and Forsling 1931). 



From 1946 through 1951, vegetal cover on 

 Watershed B was depleted to 16 percent by 

 heavy grazing, and the watershed became a 

 potential flood source. During this period 

 Watershed B produced more than four times 

 as much runoff and 12 times as much sedi- 

 ment as Watershed A. Late in 1952, Water- 

 shed B was artificially treated by disking, in- 

 stalling contour furrows on steeper slopes, 

 and seeding a mixture of adapted grasses and 

 some forbs. This restorative treatment com- 

 pletely transformed Watershed B. The disking 

 and furrowing broke up the gully system that 

 had formed when cover was sparse, and by 

 1954 an excellent stand of grass had become 

 established over most of the area. Two major 

 results of this artificial restoration of Water- 

 shed B have been: no summer storm runoff 

 since 1953; and improvement of vegetal cover 

 from a sparse stand of low-value broadleaf 

 herbs to a good stand of palatable grasses. 

 Sediment production on both Watersheds 

 now is negligible. 



Progress of the experiments on Watersheds 

 A and B was not as smooth as the preceding 

 narration may suggest. Director Sampson's re- 

 port for 1913 recounted several annoying de- 

 lays. For one thing, road conditions owing to 

 abnormal summer rainfall were such that 

 hauling a loaded wagon up Ephraim Canyon 

 could be accomplished only at long intervals. 

 Sand and cement for the bases of the steel 

 sediment catchment basins for the two Water- 

 sheds had to be hauled from Ephraim, more 

 than 10 miles away and approximately 5,000 

 feet lower. The first sediment catchment 

 basins were made from sheet steel and pro- 

 vided with weirs. They were roughly 12 feet 

 long, 5 feet wide, and 5 feet deep. Director 

 Sampson had assumed that these basins would 

 be large enough to allow the sediment in the 

 water caught on each watershed to settle suf- 

 ficiently to get a measure of the total silt. But 



he was in for a bad time. On September 1, 

 1913, just after the sediment basin on Area A 

 was installed, 0.17 inch of rain fell within a 

 very few minutes. The tank filled in approxi- 

 mately 2 minutes after the full stream reached 

 it, but the water kept pouring in for another 

 15 minutes; he reported, "It would have 

 taken at least eight tanks to have held the 

 water and silt which passed over the weir in 

 Erosion Area A." Another shower 2 days later 

 further demonstrated the inadequate size of 

 the tank; so substantially larger concrete sedi- 

 ment catchment tanks for both Areas were 

 built in 1914 (fig. 8). 



It is difficult for the uninitiated to 

 visualize what the sediment catchment tanks 

 revealed until reading a statement by Director 

 Sampson written in 1919. 



Seeing, of course, is believing, but if any- 

 one had told me that as much as a car 

 load, or approximately 50,000 pounds 

 of air dry dirt and rock would be de- 

 posited from a ten acre area from a 

 single storm I would probably be in- 

 clined to ask permission to examine the 

 figures for myself" Nevertheless air dry 

 sediment of from 20,000 to 50,000 

 pounds has been deposited several times 

 during the six years from a single 

 rainstorm. 



Figure 8. — Concrete sediment catchment tanks built 

 at low corner of Area A in 1914. 



11 



