S. Leake (USGS)

A current concern is whether or not the San Pedro River is drying out. To complement the data currently available from existing stream gauges, the goal of this task is to use new techniques to determine the spatial temporal variation of in-stream flow.

Approach

• Forty temperature sensors were installed along the San Pedro River and in tributary washes from the headwaters below Cananea, Sonora, Mexico, to the mouth near Winkleman, Arizona, U.S.A.



• Data have been collected for over a year at many locations and thermographs have been constructed. The spatial and temporal distribution of stream flow was determined by statistical analysis of the temperature data.



• Because of the relation between temperature fluctuations and stream condition, it is possible to detect the presence and absence of stream flow by monitoring streambed temperature.

Results

The research activities for the current reporting period include further data collection and analysis geared towards ending the project. All temperature probes placed in the field during the initial reporting period were removed. Results indicate that streambed temperature sensors can be used to classify stream reaches as perennial, intermittent, or ephemeral. The presence or absence of water in a stream channel will affect streambed temperature in the same way regardless of the stream channel's classification. However, due to the different flow patterns associated with each type of flow, the differences in flow patterns can be recognized on streambed thermographs.

This project has shown that low-cost temperature sensors can be used to classify flowing and non-flowing stream reaches in the desert southwest. The method can also be used to monitor how a stream channel responds to stress, such as an extended drought. By being able to delimit what reaches can potentially dry out, it is possible to recognize areas that can potentially be impacted by changes brought about by human activities.