Surface-Water Hydrodynamics and Regimes of a Small Mountain Stream-Lake Ecosystem

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Journal of Hydrology







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The hydrology of streams and lakes has been well studied as separate ecosystems; however, the behavior and implications of hydrologic linkages between these ecosystems have been little considered. We analyzed the surface-water hydrodynamics of a stream–lake ecosystem for 3 years in the Sawtooth Mountains, Idaho, USA to understand how this coupled aquatic ecosystem behaved hydrologically. This analysis included quantifying streamflow regimes above and below the lake, the expansion and contraction of the lake, stream, and floodplain, and downstream responses to snowmelt and rainstorm events. Our results showed that flow regime metrics from both hydrology and ecology were similar between above and below-lake reaches, but analysis that considered channel capacity and overbank flooding showed 2× more frequent and >5× longer duration floods below the lake compared to upstream reaches. The lake surface area expanded by as much as 19% during snowmelt runoff because of a 0.5 m rise in the lake level, and the littoral zone expanded by an even greater proportion. The lake had little influence on peakflows during spring snowmelt, though the inlet stream in the delta had a reduced flood magnitude compared to upstream stations. However, during large summer rainstorms when potential storage capacity was maximized, the lake strongly attenuated peakflows downstream from the lake. Water level changes at seven other stream–lake ecosystems in the region showed a similar range of variation. Our results provide a case study of how coupled aquatic ecosystems behave hydrodynamically and underscore the need to consider the hydrologic connections and interactions that drive aquatic ecosystems.


Originally published by Elsevier. Publisher's PDF and HTML fulltext available through remote link.