Evaluation of selected methods for determining streamflow during periods of ice effect

Abstract

Seventeen methods for estimating ice-affected streamflow are evaluated for potential use for the U.S. Geological Survey streamflow-gaging station network. The methods evaluated were identified by written responses from U.S. Geological Survey field offices and by a comprehensive literature search. The methods selected and techniques used for applying the methods are described in the report. The methods are evaluated by comparing estimated results to data collected at three streamflow-gaging stations in Iowa during the winter of 1987-88. Discharge measurements were obtained at 1-to 5-day intervals during the ice-affected periods at the three stations to define an accurate baseline record. Discharge records were compiled for each method based on data available assuming a 6-week field schedule. The methods are classified into two general categories, subjective and analytical, depending on whether individual judgement is necessary for method application. On the basis of results of the evaluation for the three Iowa stations, two of the subjective methods (discharge ratio and hydrographic-and-climatic comparison) were more accurate than the other subjective methods, and approximately as accurate as the best analytical method. Three of the analytical methods (index velocity, adjusted rating curve, and uniform flow) could potentially be used for streamflow-gaging stations where the need for accurate ice-affected discharge estimates justifies the expense of collecting additional field data. One analytical method (ice adjustment factor) may be appropriate for use for stations with extremely stable stage-discharge ratings and measuring sections. Further research is needed to refine the analytical methods. The discharge ratio and multiple regression methods produce estimates of streamflow for varying ice conditions using information obtained from the existing U.S. Geological Survey streamflow-gaging network.

Winter streamflow variability, Yukon Territory, Canada

“…Because the stage-discharge relation is not reliable under ice-cover conditions, Water Survey of Canada (WSC) subjectively interpolates winter streamflow from as few as two observations of discharge during the ice-covered season, which may last 6 months or longer. United States Geological Survey (USGS) follows similar procedures (Melcher and Walker, 1992). Figure 1 presents published WSC data for two winters.…”

“…the drop in discharge associated with the cold spell about Dec. 20. Such an assumption is common in both WSC and USGS (Melcher and Walker, 1992), despite the lack of a clearly-defined mechanism for such variations during periods of consistently sub-freezing air temperatures (Hamilton and Moore, 1996). In the 1991-92 hydrograph, the technologist has interpolated a prolonged discharge depression following the time of freeze-up.…”

Developing winter flow rating relationships using slope‐area hydraulics

“…Extensive assessments of the accuracy of various methods used to estimate daily flow based on a few winter measurements and measured daily stages have been reported by Rosenberg and Pentland (1983), Melcher and Walker (1992) and Shiklomanov et al (2006). These methods involve interpolations of such quantities as discharge ratio (actual discharge to open-water discharge at same gauge height) or backwater (actual gauge height minus open-water gauge height at same flow) between measurement dates.…”

“…In Canada, winter flow measurements are normally carried out once a month or once in 6 weeks. Melcher and Walker (1992) mention a typical 6-week measurement interval in the USA, while Shiklomanov et al (2006) indicate that 10 or more measurements per season are not uncommon in the six largest Eurasian rivers in the pan-Arctic drainage. Interpolation errors often exceed 25% and, on occasion, 50%.…”

“…Consequently, daily winter flow at any one gauge site is inferred from a few measurements that are performed during each winter period, using one of several, often subjective, interpolation methods (Melcher and Walker, 1992;Rosenberg and Pentland, 1983). None of the commonly used methods invoke basic hydraulic principles of flow under an ice cover.…”