No abstract

This paper reports the results of a six‐year study to determine interception loss in a fully stocked 65‐ to 75‐year‐old second‐growth ponderosa pine stand situated near Bass Lake, California. Interception loss was computed as the difference between measured precipitation and the sum of measured throughfall and stemflow. The average annual precipitation was 47 inches, of which about 84 pct reached the forest floor as throughfall and four per cent as stemflow. Twelve per cent was interception loss. Throughfall, stemflow, and interception loss were directly related to storm size. Regression graphs and equations based upon this relation are given, which permit estimates of interception loss from storm precipitation. An average of four per cent more precipitation reached the forest floor during snow than during rainstorms. However, estimates of annual interception loss are not appreciably improved by use of separate regressions for snowstorms and rainstorms. The interception process is illustrated by rate graphs showing when and how interception loss occurred during a typical storm. Interception loss consisted principally of the water retained by the vegetation during its initial wetting plus that lost by evaporation from the vegetation during storm intervals without precipitation.

The purpose of this paper is to discuss briefly some factors of the hydrology in the Sierra Nevada foothills of the San Joaquin Basin. The data presented are primarily concerned with the hydrologic phases of a study started by the Forest Service at North Fork, California, in 1929 to determine the influence of the woodland‐chaparral vegetation on water‐yield, surface‐runoff, and erosion. [A complete discussion of the experimental results of the North Fork study is contained in a manuscript by P. B. Rowe, “influence of woodland‐chaparral vegetation on soil‐water relations,” submitted March 1940 for publication as a U.S. Dept. Agric Tech. Bull.]

This paper presents an outline of a method of hydrologic analysis in watershed‐management. The procedure described entails the detailed accounting and evaluation of the effects of present and predicted watershed‐conditions on the course of precipitation from its occurrence to its final disposition in the watershed. The approach requires not only determination of character and extend of effects of watershed‐conditions on floods, water‐conservation, and stream‐flow, but also knowledge of physical elements and processes controlling these effects.

No abstract