The use of Streambed Temperature to Characterize the Spatial and Temporal Patterns of Ephemeral Streamflow in the Southwest

Estimates of streamflow patterns in ephemeral channels are important in predicting the upper limits of potential recharge throughout the American Southwest. Quantitative information on the frequency and duration of ephemeral stream flows is often prohibitively difficult to obtain. Conventional streamgaging techniques and analysis tools are frequently unsuccessful in these stream channels, due to the flashy nature of the streamflows. In contrast, temperature has proven to be an inexpensive, robust parameter to measure in the field. The presence or absence of streamflow within the channel may be identified by studying the diurnal signal recorded at both the streambed surface and at depth because the presence of streamflow significantly alters these diurnal temperature patterns. Longitudinal arrays of single channel recording thermistors were installed in three dry streambed channels in the American Southwest; Abo Arroyo and Isleta Arroyo, New Mexico, and the Amargosa River, Nevada, to determine the utility of the technique. Results show that a variety of analysis methods are necessary to interpret the thermal records. A suite of techniques have been developed to better understand the data and to determine the presence or absence of streamflow at given locations within the arroyos. The most promising techniques include time series analysis of multiple thermal records, and comparisons of short term thermal variance to average variances.