UNCERTAINTIES IN FLOW MODELING AND FORECASTING FOR NIAGARA RIVER
by
By Randy D. Crissman¹, and Chao-Lin Chiu², Members, ASCE, Weizu Yu³, Kazumasa Mizumura⁴, and Ion Corbu⁵

ABSTRACT

The flow in the upper Niagara River is affected by weed growth in the summer and by ice formation and accumulation in the winter. Changes in flow resistance tend to occur abruptly with time and space during ice-affected flows and make it difficult to forecast flows for power generation. Since 1988, the New York Power Authority and Ontario Hydro have collaborated on the development of a computer-based system for forecasting flows and optimizing power generation from the Niagara River. A hydraulic routing model has been developed for forecasting the flow in the upper Niagara River under uncertainties due to ice consisting of: (1) A steady-flow model; (2) an unsteady-flow routing model; (3) a linear, time-varying reservoir model for forecasting the flow into the Grass Island Pool; (4) a time-varying, stochastic model for the stage-discharge relation at Fort Erie, the upstream boundary of the reach; and (5) Kalman filtering schemes to be coupled with these components models, to reduce uncertainties in parameters and variables to be estimated. This paper presents components (2)-(5) and related concepts and modeling techniques.

INTRODUCTION

The Niagara River flows between Lakes Erie and Ontario, and is bounded on the west by the province of Ontario and on the east by the state of New York. The river is about 56 km (35 mi) long and has a total fall of about 99 m (325 ft), most of which occurs at Niagara Falls. The upper Niagara River is that portion of the river between Lake Erie and Niagara Falls (Fig. 1). The river splits into two channels around Grand Island, the east channel (Tonawanda Channel) and the west channel (Chippawa Channel), that rejoin in the Grass Island Pool (GIP). Water depths in the upper Niagara River range from about 7.5 m (25 ft) in the reach downstream of the Peace Bridge to about 2.5 m (8 ft) in the GIP. Flow velocities range from about 3.0 m/s (10 ft/sec) near the Peace Bridge to about 0.6 m/s (2 ft/sec) in the reaches adjacent to Grand Island and in the GIP. Flow in the vicinity of the Peace Bridge is relatively rapid and has been shown to have a Froude number of about 0.5, with steep hydraulic gradients. Monthly mean flows in the Niagara River have varied from about 4,800 m3/s (170,000 cfs) to over 7,300 m3/s (260,000 cfs).Propagation of a flood wave through the reach between Fort Erie and International Control Structure occurs in about 1.52 hr. Ice entering the river from Lake Erie is transported to Niagara Falls in about 12 hr.
The 1950 Treaty Between the U.S. and Canada Concerning the Uses of …