Multi-scale Approach to Hydrological Classification Provides Insight to Flow Structure in Altered River System

Abstract

Rivers are hierarchical systems exhibiting processes and patterns across spatial and temporal scales principally driven by changes in flow. Hydrological indices estimated with mean or median daily flow data (i.e. daily scale) may be insensitive to anthropogenic alteration that imparts sub‐daily variation to flow. Therefore, indices developed at multiple temporal resolutions may provide additional insight into the presence of flow patterns masked by traditional techniques. We characterized the flow regime along the longitudinal gradient of the Platte River, a large Great Plains USA river, using hydrological indices derived with mean daily and sub‐daily flow data and a combination of multivariate statistical techniques. Three unique flow units were evident using daily scale flow data, whereas six unique flow units were evident at the sub‐daily scale. Flow units at both scales were not static, but rather the presence and extent of flow units across the riverscape depended on climate, tributary inflows and human influence. Anthropogenic alteration including hydropeaking was evident at the sub‐daily scale but not at the daily scale. The full complement of flow structure within regulated rivers, therefore, may not be captured using mean or median daily discharge values alone. Inductive river classification studies may benefit from assessing hydrological indices at multiple scales, particularly when investigating river systems with anthropogenic modification such as hydropeaking. Copyright © 2016 John Wiley & Sons, Ltd.

Juvenile growth of a macrohabitat generalist tied to hydrological character of large‐river system

“…Constricted foraging opportunities during critical life‐history periods may result in reduced growth and potentially limited fecundity if individuals reach sexual maturity at smaller sizes (Matthews & Marsh‐Matthews, ). In the Platte River, constraints on food availability may exist during extreme low‐flow periods as sections of river become dry and disconnected (Spurgeon et al ., ). Riverine fishes may possess the ability to consume alternative diet items between low‐ and high‐flow periods (Balcombe et al ., ), but our results suggest growth trajectories may not be similar between these periods with potential implications for population level responses.…”

“…), is undammed with limited channelisation or bank armouring (Hamel et al ., ). Nevertheless, within the LPR, daily hydropeaking does occur as a result of the Loup River power canal system that diverts water from the Loup River and returns daily oscillations in flow to the LPR not commensurate with historical flow patterns (Hamel et al ., ; Spurgeon, Pegg & Hamel, ). Base flows are largely maintained through flow contributions from two large tributaries including the Loup River (combined with Loup power canal flows) and Elkhorn River.…”

“…Base flows are largely maintained through flow contributions from two large tributaries including the Loup River (combined with Loup power canal flows) and Elkhorn River. Hydrological modelling has suggested similar hydrological character throughout the LPR with respect to hydrological indices assessed at annual time‐steps (Spurgeon et al ., ). Mean annual discharge at the downstream most gauge location within the LPR is 204 m 3 s −1 (range = 82–459 m 3 s −1 ).…”

Assessment of a channel catfish population in a large open river system

“…Despite the connectedness throughout the lower Platte River, Barada and Pegg () suggested that population abundance and dynamics varied among sampling sites; particularly between river segments above and below the Elkhorn River confluence with the Platte River (Figure ). The Elkhorn River strongly influences hydrological differences between these sites (Spurgeon, Hamel & Pegg, ). As such, two 10‐km‐long sampling sites were selected in the lower Platte River near Louisville (rkm 26; below the Elkhorn River confluence) and Fremont (rkm 90; above the Elkhorn River confluence).…”

“…Angler distribution and exploitation data are limited for much of the Platte River system, but fishing effort is thought to be concentrated near these two urban areas that provide two of only three public access locations to the lower Platte River. The Fremont location is subject to lower water quantity and extreme diel fluctuations in the hydrograph as a result of hydropeaking from a hydroelectric dam on the Loup River power canal that diverts water from the Loup River prior to flowing into the Platte River (Hamel et al., ; Spurgeon et al., ). The Louisville site has a more stable hydrograph and greater discharge due to flow from the Elkhorn River.…”