HISTORICAL RAINFALL PATTERNS AND ARROYO ACTIVITY WITHIN THE ZUNI RIVER DRAINAGE-BASIN, NEW-MEXICO

Climate change, grazing practices, timbering activities, and erosional thresholds have been proposed to explain widespread accelerated arroyo erosion near the turn of the century in the southwestern United States. We analyze the morphology and potential causes of arroyo activity in the Zuni River drainage basin of New Mexico; our analyses illustrate the linkage between arroyos and changes that occurred through time in local precipitation patterns. Substantial archival and geological evidence confirms dominant downcutting in the intermediate and small-size arroyos within the basin for a 20- to 30-year period beginning near 1905. Historical climatic records reveal a long and severe drought from 1898-1904; this drought ended abruptly with three years dominated by unusually frequent high-intensity summer rainfall events. Daily weather records show the following two to three decades had a high number of intense summer storms, large rainfall totals, and few precipitation days. The results add support for the climate change explanation of periods dominated by arroyo incision and infilling in the southwestern U.S. © 1990 Taylor & Francis Group All right reserved.