Riparian Vegetation and Digitized Channel Variable Changes After Stream Impoundment

Following stream impoundment, rivers respond via changes in sediment dynamics, channel morphology, and vegetation distribution. Such changes have occurred along the Provo River, Utah, located within the Intermountain West of the U.S. Jordanelle Dam was built on the Provo River in 1992 after the majority of dam construction in the United States and therefore allows for a large-scale GIS analysis using aerial photographs, available before and after construction. To evaluate the effects of the dam, this study examines reach scale channel changes with respect to vegetation distribution and species richness. Post-impoundment, the authors find that channels downstream of the dam have become more stable, allowing for vegetation colonization, as exhibited in land cover changes from bare soil to grass. This results in greater species richness owing to colonization of a more stable riparian zone, ultimately changing habitat conditions. Identifying and understanding the impacts of the Jordanelle Dam on vegetation is necessary for protection of this valued ecosystem as rapid development continues.

Riparian Vegetation and Digitized Channel Variable Changes After Stream Impoundment

Following stream impoundment, rivers respond via changes in sediment dynamics, channel morphology, and vegetation distribution. Such changes have occurred along the Provo River, Utah, located within the Intermountain West of the U.S. Jordanelle Dam was built on the Provo River in 1992 after the majority of dam construction in the United States and therefore allows for a large-scale GIS analysis using aerial photographs, available before and after construction. To evaluate the effects of the dam, this study examines reach scale channel changes with respect to vegetation distribution and species richness. Post-impoundment, the authors find that channels downstream of the dam have become more stable, allowing for vegetation colonization, as exhibited in land cover changes from bare soil to grass. This results in greater species richness owing to colonization of a more stable riparian zone, ultimately changing habitat conditions. Identifying and understanding the impacts of the Jordanelle Dam on vegetation is necessary for protection of this valued ecosystem as rapid development continues.

Life history theory predicts long-term fish assemblage response to stream impoundment

Life history theory predictions for hydrologic filtering of fish assemblages are rarely tested with historical time series data. We retrospectively analyzed flow regime and fish assemblage data from the Sabine River, USA, to test relationships between life history strategies and hydrologic variability altered by impoundment construction. Downstream flow variability, but not magnitude, was altered by completion of Toledo Bend Reservoir (TBR) in 1966. Consistent with life history theory, occurrence of opportunistic strategists declined while equilibrium strategists increased as the fish assemblage was transformed between periods immediately after (1967–1973) and approximately one decade after (1979–1982) completion of TBR. Assemblage transformation was related to decline of opportunistic strategists throughout 250 km of river downstream of TBR. Temporal trajectories for opportunistic and intermediate strategist richness modelled as a function of flow variability converged 12 years postimpoundment. The spatiotemporal scaling of our study is novel among tests of life history theory, and results suggest impoundment-induced alteration to natural hydrologic filtering of fish assemblages can operate on the scale of hundreds of stream kilometres and manifest within approximately one decade.