STABLE ISOTOPES IN PRECIPITATION AND ASSOCIATED WATERS: RECORDING THE NORTH AMERICAN MONSOON IN THE FOUR CORNERS REGION, USA

The North American monsoon (NAM) is a significant summertime feature of climate in the southwestern United States (US); NAM is an eminent contributor to total annual precipitation in the Four Corners region of the US. Stable isotopic examination of precipitation, surface and ground waters is an opportunity for this under-studied region. This study characterizes the spatio-temporal changes of NAM based on stable isotopic results from 40 sites, located within the boundaries of the Navajo Nation, in Arizona, New Mexico, and Utah from 2014 to 2017. Sample collections were collected monthly at each site from May to October. Collections of surface and ground waters were collected less frequently. Investigation of temporal trends of precipitation revealed strong monthly and interannual changes; spatial analysis showed moderate large-scale relationships across the study area. Modern precipitation has an enriched stable isotopic signature, whereas, surface and ground waters show a distinct lighter isotopic signature. Analysis of stable isotopes in precipitation, surface, ground, and spring waters can be used to interpret the isotopic differences in the modern hydro-climate of the Navajo Nation and Colorado Plateau to help predict future hydro-climate changes and its implications on future water resources.