Image: Remote Sensing: "Quantifying Intermittent Flow Regimes in Ungauged Basins: Optimization of Remote Sensing Techniques for Ephemeral Channels Using a Flexible Statistical Classification" Authors: Lea J. Davis1 Adam M. Milewski1 Steven M. Holland2 1 - Water Resources & Remote Sensing Laboratory (WRRS), Department of Geology, University of Georgia, Athens, GA 30602, USA 2 - UGA Stratigraphy Laboratory, Department of Geology, University of Georgia, Athens, GA 30602, USA 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. Keywords: non-perennial channels; ephemeral; streamflow; remote sensing; discriminant function analysis; arid environments Description: This research combines remote sensing and discriminant function analysis to develop an improved classification for surface flow in ephemeral channels. Characterization of stream intermittency is crucial in dryland environments, where ephemeral channel transmission loss is the dominant form of aquifer recharge. This methodology was applied to assess temporal and spatial flow patterns across an ungauged, ephemeral system in central Morocco. From 1984 to 2022, a decreasing trend in flow frequency was identified. Flow characteristics however support continued aquifer recharge, with the majority of streamflow events concentrated during the wet season and spatially focused within the upstream channel. Decreased flow occurrence moving downstream highlights the potential impact of additional factors such as transmission loss, evapotranspiration, and agricultural abstraction contributing to channel intermittency. The application of this work further has the potential to improve management decision making in arid, data-scarce regions which lack sufficient monitoring networks. Type of News/Audience: Department News Tags: geology Research Areas: Environmental Geosciences Figure 1: The Souss channel, located in central Morocco. The channel is broken into three distinct sections based on basin morphology: upstream, midstream, and downstream. The final 16 km of the downstream section of the channel was excluded from analysis, as the reach from Drarga to the terminus at the Atlantic Ocean experiences rare surface flow and common saltwater intrusion. In the upper left, a DEM of the Souss–Massa basin displays variable elevation, ranging from 4144 m in the channel uplands to 0 m across the downstream section of the plain. Read More: MDPI - Remote Sensing
