Recent Variations in Temperature, Precipitation, and Streamflow in the Rio Grande and Pecos River Basins of New Mexico and Colorado

摘要

Trends in climatic and hydrologic data from the Rio Grande and Pecos River basin are analyzed over an approximately 40-year period (1960 to 2000). Mann-Whitney tests for changes between halves of the record and between more recent decades, and Mann-Kendall tests for trend over the 40 years of record, are applied to monthly averages from 35 temperature stations and 63 precipitation stations. Similarly, the 15 hydrometric stations meeting the criteria of the Hydro-Climatic Data Network are examined using Mann-Whitney and Mann-Kendall tests to 5-day averages of daily mean streamflow. To distinguish regions that exhibit similar patterns of climatic variation, temperature and precipitation results from the Mann-Kendall test are used as inputs to a cluster analysis. Climatic variations in the region are consistent neither through time nor across space. Some areas have demonstrated recent increases in temperature or precipitation while others have displayed decreases in these same elements. In addition, many areas reveal climatic shifts in specific periods of the year that are in marked contj-ast with the trends observed in other periods and other places. Hydrologic variations are also not spatially homogeneous, but generally indicate higher streamflow,earlier onset to freshet, and generally larger freshet volumes in more recent decades.