WATER LOSSES FROM WET AREAS 121 



A-B. However, the imderljing rock is granite and it has apparently 

 been weathered to considerable depth. The rock was found to be 

 weathered and seamed to depths of 30 feet and more in the road cuts 

 along the new Arrowhead high-gear road opposite the entrance to 

 Arrowhead Springs one mile west of the area. Hoots of chamise were 

 found in seams along the faces of the road cuts as deep as 29 feet 

 below the top of the cut. 



The capaeit}' of the soil mantle to hold moisture on the slope of a 

 mountain depends, among other things, on the soil depth. If the 

 average thickness of the soil mantle on a 45-degree slope were 2 feet, 

 the equivalent depth for the same volume of soil on a horizontal plane 

 would be 2.8 feet. Rainfall is measured by the amount falling on a 

 horizontal plane and if equivalent depth of the soil mantle on the same 

 plane be considered, it is apparent that the capacity for the storage 

 of water from rainfall as soil moisture on a slope is relatively large. 

 Water from rainfall in its movement downhill after penetrating to 

 bedrock may be intercepted and held in the pockets of deeper soil that 

 lie in the depressions through which the water moves in its progress 

 towards lower elevations. In the canyon bottom, though the rate of 

 loss is high, the area of the canyon bottom fill is but a small portion of 

 the watershed and the actual loss by evaporation and transpiration 

 from the canyon bottom vegetation is less than 2 per cent of the 

 seasonal precipitation falling on the watershed. The larger portion of 

 the precipitation must be accounted for on the drained slopes. 



Most of the steady spring flow that feeds Coldwater Creek comes 

 from the higher reaches of the canyon above an elevation of 3500 feet 

 where the seasonal precipitation is high. The source of all of the 

 steady summer flow was found to come from within an area of 0.2 

 square mile between elevations of 3100 and 4250 feet in the stream bed. 

 The area contributing to the surface drainage back of the stream bed 

 elevation of 3100 feet is 1.3 square miles and the elevation of the 

 divide ranges from 5200 to 5800 feet. The first steady stream flow in 

 Coldwater Canyon is found at an elevation of 4250 feet, yet a precipi- 

 tation of 53.66 inches was recorded at Alpine during the 1931-32 season. 

 Alpine is at an elevation of 5750 feet. There is a considerable area 

 over the divide that lies above an elevation of 4250 feet from which the 

 surface drainage waters flow northward. The close proximity of the 

 larger springs to this area of high elevation that receives a relatively 

 large amount of precipitation suggests that a considerable amount of 

 deep seepage must be occurring over this upland area. The results of 

 this investigation point to deep seepage from these upland areas above 

 an elevation of about 3500 feet as the source of most of the summer flow. 

 A more complete study should be made of this problem by tracing the 

 source of all of the summer flow coming from all of the drainage systems 

 radiating from Strawberry Peak. 



