Impact of flow regulation on stream morphology and habitat quality distribution.

The importance of interactions among stream hydrology, morphology, and biology is well recognized in studies of stream ecosystems. However, when quantifying the impacts of altered flow on aquatic habitat, results are often based either on combined changes in topography and flow, or with altered flow over static topography. Here, we study the potential beneficial effects of restoring unregulated flows on salmonid habitat and separate the relative influences of changes in flow vs.

Climate Change Shrinks and Fragments Salmon Habitats in a Snow-Dependent Region.

Climate change threatens biodiversity through global alteration of habitats, but efficient conservation responses are often hindered by imprecise downscaling of impacts. Besides thermal effects, warming also drives important ancillary environmental changes, such as when river hydrology evolves in response to climate forcing. Earlier snowmelt runoff and summer flow declines are broadly manifested in snow-dependent regions and relevant to socioeconomically important cold-water fishes.

Riparian vegetation model to predict seedling recruitment and restoration alternatives.

Native riparian vegetation communities have declined downstream of large water infrastructure like dams and diversions, owing to water management operations that prevent successful seedling colonization and recruitment. Altered timing and magnitude of reservoir releases to fulfill competing water demands often lead to reduced peak discharges and flow recession rates that do not support native riparian reproduction processes. To achieve short-term ecosystem function in highly regulated rivers an alternative method might be restoration planting, whereby success depends on identifying appropriate planting location and spatial extents.

Coupled reservoir-river systems: Lessons from an integrated aquatic ecosystem assessment.

Sustainable reservoir-river management requires balancing complex trade-offs and decision-making to support both human water demands and ecological function. Current numerical simulation and optimization algorithms can guide reservoir-river operations for optimal hydropower production, irrigation, nutrient management, and municipal consumption, yet much less is known about optimization of associated ecosystems. This ten-year study demonstrates an ecosystem assessment approach that links the environmental processes to an ecosystem response in order to evaluate the impact of climatic forcing and reservoir operations on the aquatic ecosystems of a coupled headwater reservoir-river system.

Dam operations may improve aquatic habitat and offset negative effects of climate change.

Dam operation impacts on stream hydraulics and ecological processes are well documented, but their effect depends on geographical regions and varies spatially and temporally. Many studies have quantified their effects on aquatic ecosystem based mostly on flow hydraulics overlooking stream water temperature and climatic conditions. Here, we used an integrated modeling framework, an ecohydraulics virtual watershed, that links catchment hydrology, hydraulics, stream water temperature and aquatic habitat models to test the hypothesis that reservoir management may help to mitigate some impacts caused by climate change on downstream flows and temperature.

Floodplain forest succession reveals fluvial processes: A hydrogeomorphic model for temperate riparian woodlands.

River valley floodplains are physically-dynamic environments where fluvial processes determine habitat gradients for riparian vegetation. These zones support trees and shrubs whose life stages are adapted to specific habitat types and consequently forest composition and successional stage reflect the underlying hydrogeomorphic processes and history. In this study we investigated woodland vegetation composition, successional stage and habitat properties, and compared these with physically-based indicators of hydraulic processes.

Development of a spatially-distributed hydroecological model to simulate cottonwood seedling recruitment along rivers.

Dam operations have altered flood and flow patterns and prevented successful cottonwood seedling recruitment along many rivers. To guide reservoir flow releases to meet cottonwood recruitment needs, we developed a spatially-distributed, GIS-based model that analyzes the hydrophysical requirements for cottonwood recruitment. These requirements are indicated by five physical parameters: (1) annual peak flow timing relative to the interval of seed dispersal, (2) shear stress, which characterizes disturbance, (3) local stage recession after seedling recruitment, (4) recruitment elevation above base flow stage, and (5) duration of winter flooding, which may contribute to seedling mortality.

Dynamic floodplain vegetation model development for the Kootenai River, USA.

The Kootenai River floodplain in Idaho, USA, is nearly disconnected from its main channel due to levee construction and the operation of Libby Dam since 1972. The decreases in flood frequency and magnitude combined with the river modification have changed the physical processes and the dynamics of floodplain vegetation. This research describes the concept, methodologies and simulated results of the rule-based dynamic floodplain vegetation model "CASiMiR-vegetation" that is used to simulate the effect of hydrological alteration on vegetation dynamics.