Analysis of the potential impact of development alternatives is becoming very complex with the increasing number of constraints, many of them environmental, being imposed. As well, restricted planning budgets require that a rapid identification be made of the most promising alternatives to avoid unnecessary expenditures. A screening model to quickly isolate the most promising alternatives is thus becoming of considerable importance.A computer model that satisfies these concerns in applications involving a series of reservoirs is described in the paper. The model, with both hydrologic and water quality components, simulates and thereby indicates probable changes in downstream flows, reservoir surface fluctuations, and temperature and dissolved oxygen changes in the reservoirs and streams. Through easily adjusted operating policies, reservoir sizes, etc., the model can rapidly determine the potential impact of alternative possible developments. This information is then available to biologists, wildlife, forestry, and social disciplines as an aid in their determination of the environmental impact assessments.A case study application of the model that reflects eastern Canadian conditions is described.