System Impact Assessment Model (SIAM)

The USGS Fort Collins Science Center has recently completed Version 3.4 of the Systems Impact Assessment Model (SIAM) for the Klamath River. SIAM is an integrated set of models used to address significant interrelationships among selected physical (temperature, microhabitat), chemical (dissolved oxygen, water temperature) and biological variables (young-of-year chinook salmon production), and stream flow. SIAM has been developed for the Lower Klamath River between Upper Klamath Lake, Oregon, and its outlet at the ocean in northern California, and covers a period from 1961 to near the present. These models and data have been assembled to evaluate and compare potential impacts of alternative water management alternatives from an ecological perspective.

SIAM's goal is to further the process of reaching a consensus on the management of water resources in order to stabilize and restore riverine ecosystems. SIAM should be used in the context of the Instream Flow Incremental Methodology (IFIM). As such, water management implies direct or indirect control of the quality, magnitude, duration, frequency, timing, or rate of change in river flows under man's influence. SIAM is a planning and management model rather than a research or operations model. Management models integrate the best available knowledge to provide managers with the predicted results of potential actions -- a what-if model. SIAM may be used in a planning mode by portraying the simulated effects of actions against the long-term historical backdrop. Planning models are descriptive, fostering the development of robust and non-arbitrary policies; in contrast, operational models are prescriptive and generally used to fine tune near-future actions.

SIAM starts with a water quantity model, MODSIM, to predict river flows and track reservoir volumes in the Klamath River system downstream from the U.S. Bureau of Reclamation's Klamath Project and through the reservoir complex managed by PacifiCorp. MODSIM employs a prioritization scheme to model flows throughout this system under different water management alternatives consisting of reservoir operating rules and constraints, instream flow requirements, and out-of-stream demands.

Flows simulated by MODSIM are passed to a water quality model, HEC-5Q, to predict selected water quality constituents throughout the river. For the Klamath River, the important constituents simulated are water temperature and dissolved oxygen. Fish production is dependent on micro and macro aquatic habitat, as well as the number of adult spawners. SIAM employs a fish production model, SALMOD, to predict the relative number and weight of juvenile anadromous salmonids successfully exiting the study area. It also identifies the relative magnitude of various sources of mortality (including water temperature, movement, and nesting superimposition) throughout the early life history of the species under consideration.

Collectively, SIAM's output metrics are used to characterize ecosystem health. Though not represented by a single numeric quantity, ecosystem health is embodied in the output by tallying the number of occurrences of the various metrics falling outside of user-prescribed bounds, and the physical extent of those deviations. For example, dissolved oxygen falling below 5.0 mg/l on a daily basis would be flagged as unacceptable. One of SIAM's outputs for ecosystem health is a set of "red flag" displays that capture the encroachment of standards through time and space.

Binding the models and data is the user interface for SIAM which tracks the options that the user wants to simulate, passes data and simulation results as necessary to the appropriate models, and summarizes the output for convenient display. The user interface is responsible for the almost endless bookkeeping that is required to link models together that may work off of different spatial and temporal scales, different input and output units, and different computer file formats.

Version 3.4 (August 2002) contains enhancements in several areas, most importantly a full implementation of the chinook salmon production model with parameters representative of the Klamath River. It also includes context sensitive help and easy display of mortality partitioned across lifestages and causes. As always, numerous small bugs were found and corrected.

System Impact Assessment Model (SIAM)

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