Restoring Degraded River Systems

Sustainable river system management requires a broad view of the dynamic nature of freshwater resources and the short-and long-term benefits they provide. Hydrologists, engineers, and water managers, the people who design and manage water resource systems, need to consider the impacts of their management policies and practices on ecosystems.

Economists, developers, and politicians seldom project far enough into the future to fully account for the potential ecological costs of short-term plans. Few individuals are aware of the infrastructure that brings them pure tap water or carries their wastes away, and fewer still understand the ecological tradeoffs that were made to allow these conveniences. How can society extract and use the water resources it needs while not diminishing the important natural complexity and adaptive capacity of freshwater ecosystems?

The requirements of freshwater ecosystems are often at odds with human needs, although this need not always be the case. Our current understanding of how freshwater ecosystems function allows us to elaborate the freshwater ecosystems requirements for quantity, quality, and timing of water flow. Communication of these requirements to a broad community is a critical step for including freshwater ecosystem needs in future resource allocation decisions. The public, when given information about management alternatives, will likely support ecologically based management approaches, particularly toward freshwater.

Many aquatic resources in need of restoration have problems caused by past changes in channel form or changes in flow regimes and siltation. Stream channelization, ditching in wetlands, disconnection from adjacent ecosystems, and shoreline modifications are examples of adverse changes that can degrade habitiats. Scientific and technical measures found useful in the management of restoration activities in degraded stream or river systems apply from early planning to post-implementation monitoring. Restoration activities can include upland best-management practices for agriculture, stream channel restoration, removal of exotic species and increasing native plant cover, establishing windbreaks and shelterbelts, improving upland corridors and riparian habitat, and wetland enhancement for water quality improvements. As in all management activities, the presence or absence of public support for a restoration project can make the difference between success and failure.

Restoration should reestablish the ecological integrity of degraded aquatic ecosystems. Ecological integrity refers to the natural structure, composition, and processes of biotic communities and the physical environment. Key processes, such as nutrient cycles, succession, water levels, and flow patterns, and the dynamics of sediment erosion and deposition, function within the natural range of variability. Restoration strives toward ecological integrity by taking actions that favor the desired natural processes and communities that can be sustained through time. An ecosystem in good condition is more likely to have the ability to adapt to changes.

Every degraded watershed is unique and any combination of restoration techniques or efforts may not proceed exactly as planned. Adapting a restoration policy based on system responses and new information should be considered normal. Monitoring before, during, and after some policy decision is made is crucial for finding out whether goals are being achieved. If they are not, adjustments in that policy should be undertaken. Post-project monitoring will help determine whether additional actions or adjustments are needed, and can provide useful information for future restoration efforts. This process of monitoring and adjustment is known as adaptive implementation or adaptive management. Monitoring plans should be feasible in terms of costs and technology, and should provide information relevant to meeting the restoration goals.

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