This research demonstrates the benefits of using fine-scale hydrodynamic modeling to evaluate environmental impacts of water management alternatives.
The hydrologic and geomorphic variability of rivers are both important drivers of ecological processes (citation not found: CITATION). Inter- and intra-annual flow characteristics drive many aquatic and riparian processes (citation not found: Poff1997), and alterations to a river's natural flow patterns can negatively impact many of these processes, including the timing of fish spawning (citation not found: Kiernan2012), success of riparian vegetation recruitment (citation not found: Nilsson2002), and benthic macroinvertebrate composition (citation not found: Bunn2002) (see (citation not found: Poff2010a) for a synthesis of ecological responses to altered flow).
Channel topography and composition also influence ecological processes by providing physical habitat structure (citation not found: Montgomery1999). For instance, riffle-pool-run habitat structures drive the trophic organization of aquatic species, including benthic macroinvertebrate assemblages (citation not found: Brown1991) and fish species compositions (citation not found: Schlosser1982). Floodplain soil composition and elevation are important components of the cottonwood and willow recruitment process (citation not found: Mahoney1998). And, channel type and bed composition influence fish spawning locations and abundance (citation not found: Montgomery1999a).
Although many ecological processes depend on the combined influence of hydrologic and geomorphic characteristics, environmental flow studies tend focus exclusively on assessing alterations to flow, or at a minimum consider geomorphic features as a secondary factor. And, the influence of spatial topographic variability on ecological integrity is seldom examined. This is understandable given
The hydrology and geomorphology features of a river are dynamically linked--- Flow characteristics are influenced by channel topography and composition, while
Recent environmental flow methodologies are targeted toward large-scale assessments or classifications of management impacts on riverine ecology. For instance, the Ecological Limits of Hydrologic Alterations method uses basin characteristics, climate data, and hydrology statistics to classify rivers within large geographic areas (citation not found: Poff2010). (citation not found: Arthington2006) proposed a methodology for setting regional environmental flow standards in altered systems based on comparing the frequencies of hydrologic patterns for reference rivers within a similar classification type.
Little attention has been given to the combined impacts of small to moderate hydrology alterations and landscape variability on ecological processes.