With such volumes of erosion occurring 

 year after year, it is no wonder that the range 

 on the crest of the Wasatch Plateau was seri- 

 ously depleted, that areas of bare rock ap- 

 peared frequently, or that floods to the valley 

 had been growing progressively more 

 destructive. 



The studies on Watersheds A and B have 

 shown conclusively that summer floods are a 

 direct result of reducing plant cover below 

 minimum amounts required to prevent exces- 

 sive runoff from high- in tensity summer 

 storms. Where vegetal cover has been severely 

 depleted, it is often necessary to resort to 

 contour trenching and seeding to restore satis- 

 factory watershed conditions. Because of the 

 success of this early work, few persons in val- 

 ley towns today can remember any destruc- 

 tive summer flood roaring down from the 

 mountaintop. 



Little active watershed research is current- 

 ly being carried out at the Great Basin Sta- 

 tion. A few climatic stations and rain gages 

 still collect records of physical factors, and 

 the sediment basins and weirs on Watersheds 

 A and B are being maintained. These records 

 will provide the necessary background for any 

 future watershed work that may be done on 

 the area. 



■ Infiltrometer 

 Research 



The treatments applied to Watersheds A 

 and B produced significant information about 

 the cause-and-effect relations of vegetative 

 cover to storm runoff and soil erosion. How- 

 ever, Sampson and others recognized that 

 treating instrumented watersheds was not the 

 only useful way to study problems of the 

 hydrology of rangelands. Several investigations 

 at the Great Basin Station used rainfall- 

 simulating infiltrometers, devices to apply 

 artificial "rain" to plots at predetermined 

 rates. Water and soil washed from the plots 

 are collected and the amounts of water re- 

 tained by the soil are calculated. In this way 

 the hydrologic effects of a wide range of soil 



and vegetative cover conditions can be 

 studied, as well as their effects on runoff and 

 erosion from different intensities and 

 amounts of rain. 



The major infiltrometer studies were con- 

 ducted on an area seeded to introduced 

 grasses in 1952 at the head of Manti Canyon 

 and on adjacent unseeded areas. Three years 

 after seeding there were no differences in soil 

 stability, infiltration capacity, and soil bulk 

 density between seeded and unseeded areas 

 (Orr 1957). However, 7 years after seeding, 

 differences were significant (Meeuwig 1965). 

 The seeded areas had less capillary pore space 

 and greater bulk density in the surface layers 

 of soil. This indicated that, while disking and 

 seeding effectively increased growth of forage 

 on deteriorated subalpine ranges, these treat- 

 ments should be used cautiously on areas that 

 are in good condition because they can, at 

 least temporarily, detrimentally affect infiltra- 

 tion and soil stability by reducing cover, soil 

 organic matter, and soil porosity. 



Meeuwig also found that grazing signifi- 

 cantly affected relations between plant cover, 

 soil, runoff, and erosion. The grazed plots had 

 significantly less protective soil cover, less 

 noncapillary pore space, more capillary pore 

 space, and more runoff and soil erosion than 

 the ungrazed plots. Conditions needed for 

 high water retention and soil stability under 

 heavy rainfall were found to be one or more 

 of the following: (1) bulk density of surface 4 

 inches less than 0.97, (2) protective cover of 

 litter and vegetation at least 85%, or (3) non- 

 capillary porosity of the surface 4 inches of 

 soil of at least 22 percent. If all of these con- 

 ditions are considered, then the protection re- 

 quirements in terms of each factor become 

 somewhat less stringent. 



■ Shrub 

 Plantings 



A second experiment that was part of the 

 early watershed story was a project for plant- 

 ing cuttings and sprouts of aspen (Populus 



12 



