Precipitation-Frequency Relations on the Paj arito Plateau and in the Eastern Jemez Mountains, New Mexico, and Examples of Extreme or Flood-Producing Storms

Reneau, Steven; Kuyumjian, Gregory; Malmon, Daniel; Tardiff, Mark

An analysis of annual maximum precipitation amounts for durations of 15 min to 24 hr was used to revise precipitation- frequency relations on the Pajarito Plateau and in the eastern Jemez Mountains, New Mexico, using a longer period o€record and more stations than were available in previous studies. This analysis indicates that annual maximum precipitation amounts for durations of 2 hr to 24 hr and return periods of 2 yr to 100 yr increase gradually from east to west across the study area. No sharp increase in precipitation occurs where the topography steepens in the eastern Jemez Mountains, and precipitation-distance regressions provide better predictive tools than precipitation-elevation regressions. Little or no east-to-west increase was found for 15-min and 30-rnin precipitation amounts, suggesting that the annual probability of exceeding specific 15-min or 30-min rainfall amounts is similar across the study area regardless of elevation or proximity to the range crest. The contrast in precipitation-frequency relations between durations of 1 hr is explainable by an increasing probability of multiple rainfall cells occurring in a 2-hr to 24-hr period to the west. The precipitation-frequency relations developed in this study are generally similar to published relations based on data from a larger region, although they differ from some previous local studies. Specifically, the results of this study indicate that precipitation amounts for a range of durations and return periods have been underestimated in the eastern part of the study area and overestimated in the western part in some previous studies, in turn affecting modeled estimates of runoff, erosion, and sediment transport.