Time-lapse imagery to monitor ephemeral and intermittent streams

While the interest in ephemeral and intermittent streams increased in the last few decades, monitoring such watercourses remains a major challenge in hydrology. Direct field observations are best to detect spatial patterns of flow persistence, but they are time and labour intensive and may be impractical in difficult-to-access environments. Moreover, instrumentation deployed in the riverbed can provide information about the presence/absence of water, nevertheless these methods lack in streamflow quantification. Motivated by latest advancements in computer vision hardware and software, we proposed the development and application of a stage-camera system to monitor the water level in ungauged headwater streams. This system encompasses a camera with near infrared (NIR) night vision capabilities and a pole that serves as reference object in the collected images. To evaluate the efficacy of this system in the detection of river dynamics, a set of 22 stage-camera stations was installed along the entire river network at the 4 km² Montecalvello catchment, near Viterbo (VT, Italy). Time-lapse imagery was processed through a computationally inexpensive algorithm featuring simple image-based operations. The feasibility of this approach is demonstrated through a set of benchmark measurements obtained from a supervised procedure. Preliminary evaluations are encouraging and support the usability of this approach in monitoring ephemeral and intermittent streams dynamics.