From an ecological perspective, some of the most important environments in freshwater streams are "backwaters," which usually are found at sites where water decelerates, such as at the downstream end of a bar or in a partially filled side channel. The character of these backwaters as habitats for fish and other fauna are strongly influenced by the timing, duration, and magnitude of flows. Construction of dams and other flow- control devices along streams have serious impacts on flow regimes and therefore on sediment transport, rates and forms of channel adjustment, and growth of riparian vegetation. Some research has been conducted on how changes in flows affect the character of stream channels, but many important questions remain unanswered. This doctoral dissertation research project will examine a 53-km reach of the Colorado River in western Colorado to quantify changes over the last half century in the abundance and distribution of backwaters; to correlate these changes with changes in water-use, land-use, and precipitation patterns; to study flow and sediment transport in backwaters; and to develop a model of the evolution of backwaters. The study will consist of the analysis of information from aerial photographs, public records, and field measurements of flow and sediment transport. This project will contribute to more general knowledge about the processes operating within and along streams, thereby expanding understanding of how changes in flow affect other characteristics of a stream and river dynamics and improving capabilities for predicting how proposed changes in flow regimes will affect habitats downstream. Because a number of endangered species occupy backwaters in the study area, this project will provide important information to help protect the environments occupied by these fish. As a doctoral dissertation improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.
