Five species of Pacific salmon (Oncorhynchus spp.) were radio-tagged and tracked in the mainstem Susitna River in 2012 as part of a multi-objective study to describe salmon migration behavior, identify salmon spawning locations, and evaluate techniques for future studies of salmon in turbid water. The study was conducted to support the licensing process for the proposed Susitna-Watana Hydroelectric Project. The study design allowed for comparisons to salmon distribution and habitat use in the 1980s, when similar studies were conducted for the Alaska Power Authority Hydroelectric Project. The 2012 study focused on the mainstem Susitna River due to possible effects both above and below the Project dam site where the river was separated into lower (river mile [RM] 0-98), middle (RM 98-184), and upper (upstream of RM-184) river segments.

The objective of this report is to summarize the available contemporary and historical fish and aquatic studies to support the development and implementation of studies needed to understand the potential effects of the proposed Susitna-Watana Hydroelectric Project. Because the number of studies is voluminous, the focus of this report is on the Alaska Department of Fish and Game studies conducted during the 1980s, but pertinent studies from the 1970s, late-1990s, and 2000s are also presented. The emphasis is on Pacific salmon, but a small portion covers other fishes.

The objectives of this study were as follows: (1) begin documenting the available information on mercury concentrations in various media (soil, water, fish tissue) in the Susitna drainage by other studies, and; (2) collection of fish tissue samples from the Upper Susitna basing for analyses. The 2012 study represents the first phase of this investigation. Additional phases of this work in 2013 will include sampling of soil, vegetation, water, sediment, and other media, in addition to fish tissue, to establish background mercury concentrations.

The objectives of this study are as follows: (1) provide the geomorphology team with on-the-ground preliminary observations of the role and function of wood debris in the Susitna River; (2) document and photograph occurrence and distribution of wood debris and wood debris accumulations both in-channel and on the floodplain; and (3) provide observations concerning wood debris recruitment, transport, types of accumulations, and function.

The primary goals of this study were to perform reconnaissance-level sampling to characterize local-scale riparian ecosystems (riparian ecotypes) downstream from the proposed Watana Dam site and to begin the process of mapping riparian ecotypes, wetlands, and wildlife habitats in the study area.

The specific objective of the effort presented in this technical memorandum is to perform an initial assessment of anticipated Project effects on the lower Susitna River segment channel type and morphology. The assessment was performed using the data developed for the pre- and post-Project flood frequency, flow duration, and sediment load analyses to predict the geomorphic response of the Susitna River in an analytic framework proposed by Grant et al. (2003) along the longitudinal profile of the river system from the middle Susitna River segment downstream through the lower Susitna River segment, with particular emphasis on the effects of the Chulitna and Talkeetna rivers at and downstream from the Three Rivers Confluence. This work performed for this technical memorandum integrates the results of several earlier tasks in the 2012 Reconnaissance-Level Geomorphic and Aquatic Habitat Assessment of Project Effects on Lower River Channel Study.

The objective of this analysis is to quantify the relative change in river stage at two locations in the lower Susitna River segment between the pre-Project hydrologic condition and the maximum load following OS-1 hydrologic condition. The results of the analysis provide a preliminary assessment of the change in hydraulic conditions in the lower Susitna River segment. The results will also provide a basis for interpreting how hydraulic responses to changes in hydrologic conditions can affect habitats and access to tributaries in the lower Susitna River.

The overall objective of this study is to make preliminary estimates of the overall sediment balance in the middle and lower river segments under pre-project conditions and the potential magnitude of the changes that will occur under maximum load following OS-1 hydrologic conditions, including the specific assessments of the following, interrelated topics: (1) determination of the suitability of previously published sediment transport relationships between discharge and sediment load and update the relationships if necessary; (2) selection of the most appropriate sediment transport relationships for use in the preliminary sediment balance; (3) use the selected sediment transport relationships to estimate the pre-project and maximum load following OS-1 annual loads. The sediment loads will be divided into wash load (silt and clay), sand load and gravel load; (4) comparison of estimated annual sediment loads at the three mainstem Susitna River gages to characterize the overall sediment balance under pre-project conditions and the potential changes under maximum load following OS-1 conditions.

The objective of this study is to delineate large-scale geomorphic river reaches with relatively homogeneous characteristics (e.g., channel width, lateral confinement by terraces, entrenchment ratio, sinuosity, slope, bed material, single/multiple channel, hydrology) for the purposes of stratifying the river into study segments. More specific objectives of the geomorphic reach delineation tasks are as follows: (1) develop a geomorphic classification system for the Susitna River that considers both form and process; (2) apply the classification system to delineation of geomorphic reaches in both the middle and lower Susitna River segments; (3) determine geomorphic parameters for each of the identified geomorphic reaches.