Water depth fluctuations and water chemistry in five ephemeral rock pools (tinajas), Clark County, Nevada, 2021–23

Southern Nevada is characterized by an arid climate with limited perennial water resources. In this environment, rock pools (tinajas) are both a habitat and drinking water source for wildlife. In this reconnaissance-level project, the U.S. Geological Survey studied the water depth and water chemistry at five tinajas in Clark County, Nevada. The tinaja sites in this study are representative of the dominant plunge pool morphology and the sandstone or carbonate bedrock substrates that characterize tinajas in the region. Continuous water depth measurements at four tinajas between December 2021 and December 2023 indicated that tinajas may contain water for weeks to months after being recharged but are not a permanent drinking water source for wildlife. Tinajas were driest between April and August 2022, before the beginning of the monsoon season. Chemical analysis of select nutrients, major ions, metals, and trace elements from five tinajas detected concentrations below limits established by the U.S. Environmental Protection Agency for aquatic life and drinking water.