SPILLWAY CAPACITY AND DISCHARGE UNCERTAINTY – WHY DO RATING CURVES RARELY AGREE WITH FLOW MEASUREMENT RECORDS?

摘要

Why do spillway rating curves differ from flow measurement studies or gage data? Why do rating curves often have 25% error at normal gate openings but 2% error at flood discharges? Understanding measurement uncertainty can answer these questions. This presentation compiles first-hand studies of Hells Canyon Dam, Wanapum Dam, Castlerock Dam, Petenwell Dam, and other dams. After serving as the shop manager for a university research laboratory and later transitioning to an engineering consultant, the author contends that dam owners seeking to understand rating curve discrepancies must first understand measurement uncertainty and where their rating curve originated.