Methods for estimating low-flow statistics for Massachusetts streams

Abstract

Methods and computer software are described in this report for determining flowduration, low-flow frequency statistics, and August median flows. These low-flow statistics can be estimated for unregulated streams in Massachusetts using different methods depending on whether the location of interest is at a streamgaging station, a low-flow partial-record station, or an ungaged site where no data are available. Lowflow statistics for streamgaging stations can be estimated using standard U.S. Geological Survey methods described in the report.The MOVE.1 mathematical method and a graphical correlation method can be used to estimate low-flow statistics for low-flow partialrecord stations. The MOVE.1 method is recommended when the relation between measured flows at a partial-record station and daily mean flows at a nearby, hydrologically similar streamgaging station is linear, and the graphical method is recommended when the relation is curved. Equations are presented for computing the variance and equivalent years of record for estimates of low-flow statistics for low-flow partialrecord stations when either a single or multiple index stations are used to determine the estimates.The drainage-area ratio method or regression equations can be used to estimate low-flow statistics for ungaged sites where no data are available. The drainage-area ratio method is generally as accurate as or more accurate than regression estimates when the drainage-area ratio for an ungaged site is between 0.3 and 1.5 times the drainage area of the index data-collection site.Regression equations were developed to estimate the natural, long-term 99-, 98-, 95-, 90-, 85-, 80-, 75-, 70-, 60-, and 50-percent duration flows; the 7-day, 2-year and the 7-day, 10-year low flows; and the August median flow for ungaged sites in Massachusetts. Streamflow statistics and basin characteristics for 87 to 133 streamgaging stations and low-flow partial-record stations were used to develop the equations. The streamgaging stations had from 2 to 81 years of record, with a mean record length of 37 years. The low-flow partial-record stations had from 8 to 36 streamflow measurements, with a median of 14 measurements.

Methods for estimating low-flow frequency statistics, mean monthly and annual flow, and flow-duration curves for ungaged locations in Kansas

“…Other studies have examined DARs to verify the range for which the DAR method offers estimates of low-flow statistics that are higher quality than estimates determined using regional regression equations (Eash and Barnes, 2017). Koltun and Schwartz (1987) recommended a DAR range from 0.85 to 1.15 for estimating low-flow statistics in Ohio, whereas Ries and Friesz (2000) concluded that a range from 0.3 to 1.5 was appropriate for low-flow statistics in Massachusetts (Eash and Barnes, 2017). The studies mentioned previously recommend using regression equations for ungaged locations outside of their published DAR ranges.…”

“…Several studies have reported that the DAR is ideal when the ratio is between 0.5 and 1.5 (Ries and Friesz, 2000). Many of the studies that published this guideline did not offer any scientific basis for how it was set (Ries and Friesz, 2000). This analysis concludes the DAR method or regional regression equations can be used to estimate flow statistics in Kansas based on the results of the Wilcoxon signed-rank test.…”

“…To evaluate which method, DAR or regional regression equations, is most applicable for Kansas and to determine what range is appropriate for either method, 20 pairs of streamgages were selected for testing estimates of the 7Q10 statistic following a process described by Ries and Friesz (2000) and Eash and Barnes (2017). A set of 26 streamgages composed the 20 pairs, which are listed in table 11.…”

“…Other studies have published guidelines indicating what DARs are acceptable before the use of regression equations is preferred. Several studies have reported that the DAR is ideal when the ratio is between 0.5 and 1.5 (Ries and Friesz, 2000). Many of the studies that published this guideline did not offer any scientific basis for how it was set (Ries and Friesz, 2000).…”

Streamflow, water quality, and constituent loads and yields, Scituate Reservoir Drainage Area, Rhode Island, Water Year 2017

“…Periodic manual streamflow measurements at partial-record streamgages were used concurrently with continuous-record measurements from streamgages in nearby hydrologically similar drainage areas to estimate a continuous daily record at the partial-record streamgages. Specifically, daily streamflow records for the 13 partial-record sites in the Scituate Reservoir drainage area (table 1) were estimated by using the Maintenance of Variance Extension type 1 (MOVE.1) method, as described by Ries and Friesz (2000) and Smith (2015b); data needed to estimate streamflows at partial-record sites were retrieved from the USGS National Water Information System (NWIS; U.S. Geological Survey, 2018). The upper and lower 90-percent confidence limits for the estimated mean annual streamflows, as described by Tasker and Driver (1988), are listed in table 2.…”