Cooperative Fish and Wildlife Research Units Program: all
Education, Research and Technical Assistance for Managing Our Natural Resources

Considering reservoirs as linear fragments in a basin's river network could improveunderstanding, predictability, and management efficiency. We looked for general cascading spatial patternsacross five categories of reservoir attributes: land cover, morphology and hydrology, fish habitat, fishassemblages, and fisheries. Attributes were pulled from various databases for large reservoirs (>100 ha) locatedin the United States. 16 widely distributed river basins, each including a minimum of 15 large reservoirs, wereselected for analysis. Using analysis of covariance with basin as the class variable, we tested each attribute as alinear function of catchment area, which is an index of reservoir position in the basin. The majority of reservoirattributes displayed log-linear patterns as catchment area increased, indicating that reservoirs act as membersof a larger network just as river reaches do. Several patterns were detected including attributes with no apparentlengthwise arrangement along the basin; cascading spatial patterns in which attributes increase or decreasefrom upstream to downstream within a basin; and attributes that increase with catchment area in some basins,decrease in others, or may simply remain constant throughout the basin. We conclude that each pattern mayhave different implications for management, and that the effectiveness with which most management activitiesinfluence reservoirs is likely to increase or decrease along river basins.