New field method to determine streamflow timing using electrical resistance sensors

Electrical resistance (ER) sensors were constructed to monitor streambed saturation to infer ephemeral streamflow timing. The sensors were evaluated in an ephemeral stream through comparison with temperature-based methods, a stream gauge, and soil water content sensors. The ER sensors were more accurate at estimating streamflow timing and the resultant data required less interpretation than data from temperature-based methods. Accuracy was equivalent to timing methods using stream gauge and soil water content measurements. The ER sensors are advantageous for use in ephemeral stream channels because they are inexpensive, deployable above or below the sediment surface, insensitive to depth, and do not require connecting wires to an external datalogger or power source. On the basis of these results, we conclude that ER sensors may be used to monitor changes in soil water content within the vadose zone. Additionally, the sensors can be used to infer the presence of surface water in diversion canals, storm-water sewers, and in the form of overland runoff.