Glen Canyon Dam Adaptive Management Program Administrative History

This brief article, written for a symposium on "Collaboration and the Colorado River," evaluates the U.S. Department of the Interior's Glen Canyon Dam Adaptive Management Program ("AMP"). The AMP has been advanced as a pioneering collaborative and adaptive approach for both decreasing scientific uncertainty in support of regulatory decision-making and helping manage contentious resource disputes -- in this case, the increasingly thorny conflict over the Colorado River's finite natural resources. Though encouraging in some respects, the AMP serves as a valuable illustration of the flaws of existing regulatory processes purporting to incorporate collaboration and regulatory adaptation into the decision-making process. Born in the shadow of the law and improvised with too little thought as to its structure, the AMP demonstrates the need to attend to the design of the regulatory process and integrate mechanisms that compel systematic program evaluation and adaptation. As such, the AMP provides vital information on how future collaborative experiments might be modified to enhance their prospects of success.

It is apparent that before emplacement of the dam gully degradation in terraces was restored by periodic alluvial deposition from river floods, but perhaps even more important is the redistribution of flood sands onto higher terraces by wind. Thus, we propose the term "restorative base-level hypothesis" to emphasize the dynamic equilibrium between gully erosion and renewed deposition, a process that remains active in Cataract Canyon but is disrupted in Grand Canyon by the presence and operation of the dam.

We developed type geomorphic settings to develop a conceptual process model for the diverse small-catchment geomorphic system in Grand Canyon. Research findings explain how streams are able to cross broad, flat terraces given a rainfall event and how they become progressively more integrated with the river. The primary channelization processes are ponding and overflow, alluvial fan progradation, and infiltration and piping, all of which contribute to nickpoint migration. An understanding of these processes was essential to building the geomorphic model.

The predictive mathematical model quantifies erosional vulnerability by applying a hypothetical rainfall event of 25 mm/hour onto a catchment above a "pristine" terrace sequence. The principal driving factor for erosion is basin area. The principal resisting factor for erosion is terrace diffusion capacity, which is a function of terrace sand cross-sectional area and infiltration capacity. Several important modifying factors are applied to the basic model to determine relative vulnerability of each terrace to gully erosion. Vulnerability of the top terrace at each catchment is plotted against the measured amount of gully erosion in that terrace, providing a base line against which progressive changes in gully depth can be easily monitored in the future.

Field studies and research show that: (1) gully erosion of terraces has been severe during the past 20 years in Grand Canyon due to unusually high precipitation; and (2) sediment deprivation coupled with the lack of large annual floods has caused a reduction in restorative (depositional) factors. Continued measurement and documentation of geomorphic processes in catchments, particularly at type geomorphic settings, will further refine and verify the predictability of the model. We conclude that beach-habitat-building flows are essential for initiating natural restorative processes and that one of the most important processes in gully mitigation may be eolian reworking of newly deposited flood sands onto higher terraces. Prior to the construction of Glen Canyon Dam, gully-deepening and river/wind depositional processes were in dynamic equilibrium, allowing the preservation of ancient cultural sites for the past several thousand years.

Vegetation changes in the canyon of the Colorado River between Glen Canyon Dam and Lake Mead were studied by comparing photo­ graphs taken prior to the completion of the Glen Canyon Dam in 1963 with those taken afterwards at the same sites. The old photo­ graphs, taken by J. K. Millers, T. H. O'Sullivan, William Bell, F. A. Nims, R. B. Stanton, N. W. Carkhuff, N. H. Darton, L. R. Freeman, E. C. LaRue, and others, document conditions as they were between 1872 and 1963. In general, the older pictures show an absence of riparian plants along the banks of the river. The new photographs of each pair were taken in 1972 through 1976. The most obvious vege­tation change revealed by the photograph comparison is the in­ creased density of many species. Exotic species, such as saltcedar and camelthorn, and native riparian plants, such as sandbar willow, arrowweed, desert broom, and cattail, now form a new riparian com­munity along much of the channel of the Colorado River between Glen Canyon Dam and the Grand Wash Cliffs.

The matched photographs also reveal that changes have occurred in the amount of sand and silt deposited along the banks. The photo­ graphs show that in some areas erosion has been significant since the time of the earlier photograph while at other locations sediment has accumulated on river bars and terraces. Detailed maps are presented showing distribution of 25 plant species. Some of these, such as Russian olive and elm, were unknown along the Grand Canyon reach of the Colorado River before 1976.

Relevant data are presented to show changes in the hydrologic regime since completion of Glen Canyon Dam. Flooding, as expressed by annual maximum stage, has decreased in amplitude, and its sea­ son of occurrence has changed from spring (May-June) to a longer period from April through October. Dam construction has had a moderating influence on several other hydrologic variables. Com­pared to the predam era, discharge through the year now varies within narrow limits, changing little from month to month or season to season; annual maximum discharges are now strikingly uniform, and sediment load has materially decreased. Increases have occurred in some characteristics, however, such as daily variation in river stage and median discharge.

The interaction of decreased flooding, decreased sediment load, and increased riparian plant coverage makes the future of existing river fans, bars, and terraces uncertain. The establishment of a new ecological equilibrium at the bottom of the Grand Canyon may re­ quire many decades.

The Glen Canyon Dam Adaptive Management Program (AMP) has been identified as a model for natural resource management. We challenge that assertion, citing the lack of progress toward a long-term management plan for the dam, sustained extra-programmatic conflict, and a downriver ecology that is still in jeopardy, despite over ten years of meetings and an expensive research program. We have examined the primary and secondary sources available on the AMP’s design and operation in light of best practices identified in the literature on adaptive management and collaborative decision-making. We have identified six shortcomings: (1) an inadequate approach to identifying stakeholders; (2) a failure to provide clear goals and involve stakeholders in establishing the operating procedures that guide the collaborative process; (3) inappropriate use of professional neutrals and a failure to cultivate consensus; (4) a failure to establish and follow clear joint fact-finding procedures; (5) a failure to produce functional written agreements; and (6) a failure to manage the AMP adaptively and cultivate long-term problem-solving capacity.

Adaptive management can be an effective approach for addressing complex ecosystem-related processes like the operation of the Glen Canyon Dam, particularly in the face of substantial complexity, uncertainty, and political contentiousness. However, the Glen Canyon Dam AMP shows that a stated commitment to collaboration and adaptive management is insufficient. Effective management of natural resources can only be realized through careful attention to the collaborative design and implementation of appropriate problem-solving and adaptive-management procedures. It also requires the development of an appropriate organizational infrastructure that promotes stakeholder dialogue and agency learning. Though the experimental Glen Canyon Dam AMP is far from a success of collaborative adaptive management, the lessons from its shortcomings can foster more effective collaborative adaptive management in the future by Congress, federal agencies, and local and state authorities.