This report summarizes a workshop held to identify monitoring indices for ecosystem change in response to flow.

The Instream Flow Needs Technical Task Group (IFNTTG) of the Cumulative Environmental Management Association (CEMA) hosted a workshop in Calgary, Alberta on March 27-28, 2007 to assist in the development of this monitoring program. The primary objective of the workshop was to identify monitoring indices that provide an understanding of how the LAR ecosystem responds to changes in flow. The workshop focused on articulating the questions and scientific uncertainties to be addressed and resolved by the monitoring program, and identification of the ecosystem components that would be monitored. Thirteen experts from a variety of institutions across North America attended the workshop. A key feature of the workshop approach was to develop a conceptual model, which is simply a set of verbal descriptions of potential impacts of water withdrawals on key physical and biological indicators (e.g. fish population size or recruitment rate). Initial scoping discussions had suggested that the conceptual model should concentrate on prediction of possible impacts of winter flows on the mainstem Athabasca River, mainly in terms of changes in indicator fish populations. But comments from experts in the workshop soon made it apparent that such a narrow definition of the problem would lead to high risk of overlooking important potential impacts and separating effects of flow withdrawal from other, ongoing changes in the Athabasca River basin. Workshop participants articulated six main impact hypotheses describing the effects of reduced flow in the lower Athabasca River on physical and biological resources: 1) loss of connectivity between tributary and mainstem for spawning, rearing or overwintering of fishes; 2) loss of connectivity within the mainstem during winter; 3) loss of connectivity among delta features and between side channels and the mainstem; 4) reduced habitat availability in the mainstem; 5) reduced water quality; and 6) changes in water temperature. Confounding factors that need to be considered by a monitoring program aimed at assessing effects of flow change included changes in: dissolved oxygen levels in tributaries; long-term water yield; tributary hydrology and habitat; toxicity; and, fishing pressure. Final recommendations and conclusions from invited experts were provided at the end of the workshop and are summarized in Section 4.0.