Flow of springs and small streams in the Tecolote Tunnel area of Santa Barbara County, California

Abstract

This report presents the results of an investigation to determine the effect of the construction of Tecolote Tunnel in southern Santa Barbara County, Calif., on the flow of springs and spring-fed streams in the tunnel area. A program of monthly measurement of discharge for this purpose began in late 1948 at 125 springs and streams; tunnel construction started in March 1950 and was completed in January 1956. By late 1951 an appreciable amount of seepage was entering the tunnel. Incidental to the primary objective of this study, but necessary to the investigation, were a study of the discharge pattern of the springs and streams of the region and an evaluation of the effect on flow of both the Arvin-Tehachapi earthquake of July 21, 1952 and the Refugio brush fire of early September 1955. The most striking characteristic of the flow regimen in the area is the rapid response of discharge to precipitation. An interesting effect was observed in July 1952 when the Arvin-Tehachapi earthquake abruptly increased the flow at 18 measuring sites. At 15 of these sites this effect was felt for only several months, but at three of the sites the effect remained for several years. As for the effects of the Refugio flre, there is some reason to believe that the summer flow of many springs and streams may have increased in succeeding years as a result of decreased evapotranspiration losses, but the evidence is inconclusive. The many complex and interrelated factors that influence the discharge of springs and spring-fed streams make it exceedingly dimcult to isolate the effect of Tecolote Tunnel on the flow. Another major difficulty in an evaluation of the effect of the tunnel stems from the fact that the calibration period for this study was only 3 years, lasting from late 1948 to late 1951, during which time the precipitation was uniformly deficient. Furthermore, these inadequacies of the calibration period in regard to short length of record and limited range in precipitation, cannot be overcome by the collection of additional discharge information in the years to come. From the data available, however, the following conclusions were reached concerning the effect of Tecolote Tunnel : 1. The failure of one spring can be attributed to construction of the tunnel. This spring, designated as site llOb, is the source of Hot Springs Creek. 2. There is no evidence that construction of the tunnel affected the flow of any other spring or stream. Bl R2 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES