Quantifying Intermittent Flow Regimes in Ungauged Basins: Optimization of Remote Sensing Techniques for Ephemeral Channels Using a Flexible Statistical Classification

Abstract

Intermittent and ephemeral channels are a critical component of the global hydrologic network. The dominant feature in dryland environments, ephemeral channel transmission loss facilitates aquifer recharge. Characterizing flow intermittency improves groundwater storage estimates; however, limited gauging of intermittent systems impedes this understanding. This research develops an improved classification for surface flow, optimized for ephemeral systems using linear discriminant function analysis and remotely sensed imagery. It further applies this methodology to assess temporal and spatial flow patterns across the Souss channel, an ungauged, ephemeral system in central Morocco. Linear discriminant function analysis demonstrates high predictive accuracy for Landsat imagery, with significantly improved classification success as compared to the Modified Normalized Difference Water Index. Application to the Souss channel from 1984 to 2022 points to a decreasing trend in flow frequency. Despite this change, flow events remain concentrated within the wet season, critical for regional aquifer recharge. Spatial flow characteristics further support sustained infiltration, with the majority of events focused within the upstream channel section during both dry and wet seasons. Decreased occurrence moving downstream highlights the likely impact of additional factors such as transmission loss, evapotranspiration, and agricultural abstraction contributing to channel intermittency.

How well can people observe the flow state of temporary streams?

“…Low-cost sensors have been developed to investigate the high spatial variability in the flow states of temporary streams (Goulsbra et al, 2009;Bhamjee and Lindsay, 2011;Jaeger and Olden, 2012;Assendelft and van Meerveld, 2019;Kaplan et al, 2019) but their use is still restricted to experimental studies. The flow state of temporary streams can also be determined from aerial photographs (Spence and Mengistu, 2016;Borg Galea et al, 2019;Davidson et al, 2023). However, this method cannot be applied in forested areas, and its temporal resolution does not allow studying state changes during storm events (Jensen et al, 2019;Kaplan et al, 2019).…”