Local subbasin characteristics are determinants of streamflow intermittency in the Huachuca Mountains, Arizona, USA

Abstract:

Intermittent and ephemeral streams account for over half of the total discharge of the global river network and their extent is expected to increase as a result of forecasted changes in climate and water resource development. Recognizing the importance of stream flow as the master variable driving physical, chemical, and biological processes in fluvial systems there is inherent utility in predicting which regions of the landscape support varying degrees of flow permanence (e.g., perennial, intermittent, and ephemeral flow). Easily derivable landscape characteristics and readily available climate data may be useful for identifying streamflow permanence. We use local precipitation records and GIS-derived geologic and topographic descriptors to identify potential determinants of flow permanence in streams draining the Huachuca Mountains, Arizona, USA. Flow permanence is based on 2- to 4-year time series for 43 electrical resistance sensors installed across 10 canyons in stream reaches that support a range of hydrologic flow conditions. Multivariate NMDS analysis identifie separation between stream reaches of different flow permanence classes based on subbasin-scale, GIS-derived landscape metrics. In particular, separation between perennial and ephemeral reaches is driven by steep surface slopes and small drainage areas that support perennial flow and which correspond to the location of specific geologic units. Ephemeral and intermittent reaches are also highly responsive to precipitation events, specifically, late summer convective thunderstorms with spatial extents limited to individual canyons or portions of a canyon. Further separation of landscape and precipitation characteristics is expected between flow classes that account for refined flow permanence metrics including seasonal timing and duration of flow. Our results demonstrate that for this system, easily derivable metrics and available climate data serve as useful metrics for prediction of flow permanence.