Muskoka watershed management model

Abstract

The Muskoka River Basin in central Ontario covers an area of approximately 4,700 km. The water resources of this basin are important not only for the year-round residents of the area, but also for many thousands of summer residents and tourists who take advantage of available recreational activities and facilities. The watershed extends from the western portion of Algonquin Park to Georgian Bay and drops approximately 1,300 feet in elevation. Water resources management within the basin is particularly complex. There are 34 control structures operated by four agencies, two locks for pleasure craft, 26 major lakes and nine hydro power stations operated by three utilities. Competing water use interests include recreation (including sportfishing), navigation, hydro power, flood control, and water supply. The responsibility for wrater allocation and management of almost alI control structures lies with the Ministry of Natural Resources. Significant efforts have been made by all interests to resolve possible conflict in water allocation, and present Ministry policies have been successful in satisfying most water allocation demands. However, population and recreation pressures, rising energy costs, and sensitivity to fisheries and other environmental constraints, have increased pressure to further improve the basin management. The preparation of a major mathematical model of basin operations has been commissioned in order to review past policies in the allocation of water, and to improve floodhandling and other specific concerns. The model selected for this purpose is a modification of the Trent River system operating model, which has been in use for a number of years. Major modifications were required to adapt this model to the complexity of the Muskoka Basin, to allow detailed specifications of various competing interests, and to produce the most convenient output for Ministry staff. In addition to easing the day-to-day operational planning for the basin, it is anticipated that, by tests examining different operating priorities, improved methods of allocation will result in overall optimization of watershed resources. The- mathematical model is now largely completed and undergoing testing and calibration. Major components of the background study include the following: - physical data base compilation - historical basin ooerations description - model structure development - subbasin hydrologic modeling - model calibration. Each of the above components is described in the paper, along with sample results from the hydrologic studies and basin simulation calibration which have been carried out. The present status of model development is explained, along with a description of the projected work program for the coming summer season. Specific difficulties which have been encountered due to the complexity of the model, and the strict operation rules which must be followed, are outlined. The basin is presently being managed by the Ministry of Natural Resources using traditional operating rules and resource allocation priorities. In parallel with this manual system, Ministry staff are operating the mathematical model in order to compare results, suggest operations and to assist in the development and calibration of specific model routines. It is expected that by the end of 1982 model development will be completed to the extent that day-to-day operation of the basin can be performed according to model output instructions, with only extreme events requiring manual intervention. Future improvements for the model are also planned. These may include storm handling, detailed studies of the effects of alternative rule curves, examination of the priorities assigned to various water uses, and the implementation of possible structural works to assist in flood control and power generation optimization. © 1982 Taylor & Francis Group, LLC.