Comparison of wet/dry mapping and electrical resistivity sensors to characterize patterns of intermittency

Abstract:

Intermittent rivers are those that cease to flow at some point(s) in space and time along their course and are present in all climates and terrestrial biomes. The prevalence of drying is increasing, even in temperate biomes that we typically do not associate with river drying or dry climates. There have been several techniques employed to characterize patterns of intermittency but field mapping and use of electrical resistivity (ER) sensors are the most common. Field mapping has long been used to study intermittency, but this method is limited by its inability to capture the rapidly changing configuration of intermittent streams that often occur during wetting and drying events. ER sensors enable researchers to remotely record channel-water presence at fine spatiotemporal scales which will better capture seasonal dynamics in transient lotic systems. Here, we compare field mapping and ER sensor recordings of stream intermittency for 10 forested headwater streams in northeastern Ohio. Field mapping occurred approximately biweekly while the ER sensors recorded at 30-minute intervals from April through November 2014. Although ER sensors offer many advantages to stream mapping, our study revealed several limitations of ER sensors including requiring re-securing after flows moved sensors, burial in sediment that results them in recording subsurface water, and the small spatial scale the sensors are representative of. Nevertheless, ER sensors provide a low cost, high performance, and method that requires minimal data interpretation to monitor the presence and absence of water in channels at a specific location. The latest generation of ER sensors also record temperature, which can help in differentiate standing and flowing water. Aspects other than timing, duration, and frequency of flow such as the resumption (advancing) and recession (retreating) rates or magnitudes can be characterized with ER sensor arrays.