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OJ)\}379 . probably resulted in excessive stream losses because some of the phreato- phyte areas may not have been using water at the full potential rate. On the basis of the available data, stream losses in the reach between Johnson Canyon and Highway 666 were estimated to be about 2,400 acre- feet per year. Stream losses for the other reaches were calculated propor- tionately, based on the measured phreatophyte and water surface area in each reach. The adopted monthly stream losses used in the virgin flow analysis are shown on Table 12. . Short-Term Runoff Events The flow of the Mancos River during summer and fall is affected by short- term duration runoff events. Runoff from summer rainstorms is very sporadic, and in some years it is negligible. In other years such as 1970, it is estimated that short-term runoff from thunderstorms constitutes over 15 percent of the annual flow. Runoff from thunderstorms is characterized by a high-rate discharge that quickly peaks and then recedes within a period of approximately one week. The estimate of short-term runoff was calculated for the reach between the confluence of West, Middle, and East Mancos rivers and the USGS gage near the Highway 666 bridge, as described in Section A. Section B describes the estimation of short-term runoff for each specific reach of the Mancos River. Since runoff from short-term rainfall events in the summer and fall is ephemeral, it may be impractical to design irrigation or industrial diversion facilities to divert much of this flow. Therefore, separate monthly summaries of Mancos River virgin flow have been prepared both with and without the inclu- sion of short-term runoff. A. Calculation of Short-Term Runoff. The USGS gage records for the Mancos River near Towaoc, located near the Highway 666 bridge, were analyzed on a daily basis to determine the amount of incremental flow associated with short-term runoff events. . -33- !:.