Sources of Uncertainty in Canadian Low Flow Hydrometric Data

Tic uncertainty of estimated daily mean discharge is 5% at the 95% confidence interval (Herschy, 1.999a). The use Of this unique value requires acceptance of the assumption Of uniformity of uncertainty within the hydrometric dataset. It is the implicit responsibility of each researcher to challenge this assumption with respect to any given hypothesis test. This paper evaluates this assumption of uniformity for a subset of the hydrometric dataset-low flow in Canada. Studies of low flow phenomena are becoming more prevalent with increasing recognition of the importance of low flows for viable ecosystems and sustainable economics and as a sentinel of change. Environmental and operational circumstances are identified that elevate the opportunity for error with respect to measurement of low flows. These factors are examined qualitatively and are found to exist throughout all steps of the data production process. The uncertainty of low flows in Canada is very likely different from the uncertainty of the global hydrometric dataset. The magnitude of low flow uncertainty remains undefined because no field experiments were conducted as part of this study. It is hoped that these findings will inspire the design Of future research needed to overcome this deficiency.