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Charles Parrett

Publications and source records attributed to Charles Parrett.

At least 55 records · Page 3Linked to original sources
USGS1989

Methods for estimating monthly streamflow characteristics at ungaged sites in western Montana

Three methods were developed for estimating monthly streamflow characteristics for western Montana. The first method, based on multiple-regression equations, relates monthly streamflow characteristics to various basin and climatic variables. Standard errors range from 43 to 107%. The equations are generally not applicable to streams that receive or lose water as a result of geology or that have appreciable upstream storage or diversions. The second method, based on regression equations, relates monthly streamflow characteristics to channel width. Standard errors range from 41 to 111%. The equations are generally not applicable to streams with exposed bedrock, with braided or sand channel, or with recent alterations. The third method requires 12 once-monthly streamflow measurements at an ungaged site. They are then correlated with concurrent flows at some nearby gaged site, and the resulting relation is used to estimate the required monthly streamflow characteristic at the ungaged site. Standard errors range from 19 to 92%. Although generally substantially more reliable than the first or second method, this method may be unreliable if the measurement site and the gage site are not hydrologically similar. A procedure for weighting individual estimates, based on variance and degree of independence of individual estimating methods, was also developed. Standard errors range from 15 to 43% when all three methods are used. The weighted-average estimated from all three methods are generally substantially more reliable than any of the individual estimates.

Western Montana↗
USGS1989

Estimates of monthly streamflow characteristics at selected sites in the upper Missouri River basin, Montana, base period water years 1937-86

Estimates of streamflow characteristics (monthly mean flow that is exceeded 90, 80, 50, and 20 percent of the time for all years of record and mean monthly flow) were made and are presented in tabular form for 312 sites in the Missouri River basin in Montana. Short-term gaged records were extended to the base period of water years 1937-86, and were used to estimate monthly streamflow characteristics at 100 sites. Data from 47 gaged sites were used in regression analysis relating the streamflow characteristics to basin characteristics and to active-channel width. The basin-characteristics equations, with standard errors of 35% to 97%, were used to estimate streamflow characteristics at 179 ungaged sites. The channel-width equations, with standard errors of 36% to 103%, were used to estimate characteristics at 138 ungaged sites. Streamflow measurements were correlated with concurrent streamflows at nearby gaged sites to estimate streamflow characteristics at 139 ungaged sites. In a test using 20 pairs of gages, the standard errors ranged from 31% to 111%. At 139 ungaged sites, the estimates from two or more of the methods were weighted and combined in accordance with the variance of individual methods. When estimates from three methods were combined the standard errors ranged from 24% to 63 %. A drainage-area-ratio adjustment method was used to estimate monthly streamflow characteristics at seven ungaged sites. The reliability of the drainage-area-ratio adjustment method was estimated to be about equal to that of the basin-characteristics method. The estimate were checked for reliability. Estimates of monthly streamflow characteristics from gaged records were considered to be most reliable, and estimates at sites with actual flow record from 1937-86 were considered to be completely reliable (zero error). Weighted-average estimates were considered to be the most reliable estimates made at ungaged sites. (USGS)

Water-Resources Investigations Report↗
USGS1989

Estimates of mean monthly streamflow for selected sites in the Musselshell River basin, Montana, base period water years 1937-86

Estimates of mean monthly and mean annual streamflow were made for 56 selected sites in the Musselshell River basin and 1 site outside the basin. The study area was divided into a Mountain Region and a Plains Region and the estimation methods were applied separately in the two regions. Four methods were developed to estimate mean monthly streamflow at ungaged sites. The first method was based on the regression relation between mean monthly streamflow and various basin and climatic characteristics. The standard errors ranged from 35 to 71% in the Mountain Region and from 98 to 157% in the Plains Region. The second method was based on the regression relations between mean monthly streamflow and active-channel width. The standard errors ranged from 38 to 81% in the Mountain Region and from 71 to 98% in the Plains Region. The third method was based on correlation of measured streamflow at ungaged sites with concurrent daily mean streamflow at nearby gaged sites. The standard errors ranged from 36 to 66% in the Mountain Region and from 109 to 321% in the Plains Region. The fourth method, generally the most reliable, estimated mean monthly streamflows by weighing individual estimates in accordance with their variance and degree of independence. The standard error for this method when all three individual estimates were weighed ranged from 25 to 55% in the Mountain Region and from 71 to 97% in the Plains Region. (USGS)

Water-Resources Investigations Report↗
USGS1987

Revised techniques for estimating peak discharges from channel width in Montana

This study was conducted to develop new estimating equations based on channel width and the updated flood frequency curves of previous investigations. Simple regression equations for estimating peak discharges with recurrence intervals of 2, 5, 10 , 25, 50, and 100 years were developed for seven regions in Montana. The standard errors of estimates for the equations that use active channel width as the independent variables ranged from 30% to 87%. The standard errors of estimate for the equations that use bankfull width as the independent variable ranged from 34% to 92%. The smallest standard errors generally occurred in the prediction equations for the 2-yr flood, 5-yr flood, and 10-yr flood, and the largest standard errors occurred in the prediction equations for the 100-yr flood. The equations that use active channel width and the equations that use bankfull width were determined to be about equally reliable in five regions. In the West Region, the equations that use bankfull width were slightly more reliable than those based on active channel width, whereas in the East-Central Region the equations that use active channel width were slightly more reliable than those based on bankfull width. Compared with similar equations previously developed, the standard errors of estimate for the new equations are substantially smaller in three regions and substantially larger in two regions. Limitations on the use of the estimating equations include: (1) The equations are based on stable conditions of channel geometry and prevailing water and sediment discharge; (2) The measurement of channel width requires a site visit, preferably by a person with experience in the method, and involves appreciable measurement errors; (3) Reliability of results from the equations for channel widths beyond the range of definition is unknown. In spite of the limitations, the estimating equations derived in this study are considered to be as reliable as estimating equations based on basin and climatic variables. Because the two types of estimating equations are independent, results from each can be weighted inversely proportional to their variances, and averaged. The weighted average estimate has a variance less than either individual estimate. (Author 's abstract)

Water-Resources Investigations Report↗
USGS1986

Estimated monthly percentile discharges at ungaged sites in the upper Yellowstone River Basin in Montana

Once-monthly streamflow measurements were used to estimate selected percentile discharges on flow-duration curves of monthly mean discharge for 40 ungaged stream sites in the upper Yellowstone River basin in Montana. The estimation technique was a modification of the concurrent-discharge method previously described and used by H.C. Riggs to estimate annual mean discharge. The modified technique is based on the relationship of various mean seasonal discharges to the required discharges on the flow-duration curves. The mean seasonal discharges are estimated from the monthly streamflow measurements, and the percentile discharges are calculated from regression equations. The regression equations, developed from streamflow record at nine gaging stations, indicated a significant log-linear relationship between mean seasonal discharge and various percentile discharges. The technique was tested at two discontinued streamflow-gaging stations; the differences between estimated monthly discharges and those determined from the discharge record ranged from -31 to +27 percent at one site and from -14 to +85 percent at the other. The estimates at one site were unbiased, and the estimates at the other site were consistently larger than the recorded values. Based on the test results, the probable average error of the technique was + or - 30 percent for the 21 sites measured during the first year of the program and + or - 50 percent for the 19 sites measured during the second year.

Montana↗
USGS1986

Methods for estimating magnitude and frequency of floods in Montana based on data through 1983

Equations are presented for estimating flood magnitudes for ungaged sites in Montana based on data through 1983. The State was divided into eight regions based on hydrologic conditions, and separate multiple-regression equations were developed for each region. These equations relate annual flood magnitudes and frequencies to basin characteristics and are applicable only to natural-flow streams. In three of the regions, equations also were developed relating flood magnitudes and frequencies to basin characteristics and channel-geometry measurements. The standard errors of estimate for an exceedance probability of 1 percent ranged from 39 to 87 percent. Techniques are described for estimating annual flood-magnitude and flood-frequency information at ungaged sites based on data from gaged sites on the same stream. Included are curves relating flood-frequency information to drainage area for eight major streams in the State. Maximum known flood magnitudes in Montana are compared with estimated 1-percent-chance flood magnitudes and with maximum known floods in the United States. Values of flood magnitudes for selected exceedance probabilities and values of significant basin characteristics and channel-geometry measurements for all gaging stations used in the analysis are tabulated. Included are 375 stations in Montana and 28 nearby stations in Canada and adjoining States.

Montana↗
USGS1986

Simulation of rain floods on Willow Creek, Valley County, Montana

The Hydrologic Engineering Center-1 rainfall-runoff simulation model was used to assess the effects of a system of reservoirs and waterspreaders in the 550-sq mi Willow Creek Basin in northeastern Montana. For simulation purposes, the basin was subdivided into 100 subbasins containing 84 reservoirs and 14 waterspreaders. Precipitation input to the model was a 24-hr duration, 100-yr frequency synthetic rainstorm developed from National Weather Service data. Infiltration and detention losses were computed using the U.S. Soil Conservation Service Curve Number concept, and the dimensionless unit hydrograph developed by the U.S. Soil Conservation Service was used to compute runoff. Channel and reservoir flow routing was based on the modified Puls storage routing procedure. Waterspreaders were simulated by assuming that each dike in a spreader system functions as a reservoir, with only an emergency spillway discharging directly into the next dike. Waterspreader and reservoir volumes were calculated from surface areas measured on maps. The first simulation run was made with no structures in place, and resulted in a 100-yr frequency peak at the mouth of Willow Creek of 22,700 cu ft/sec. With all structures in place, the 100-yr frequency peak was decreased by 74% to 5,870 cu ft/sec. (USGS)

Water-Resources Investigations Report↗
USGS1985

A method for estimating mean and low flows of streams in national forests of Montana

Equations were developed for estimating mean annual discharge, 80-percent exceedance discharge, and 95-percent exceedance discharge for streams on national forest lands in Montana. The equations for mean annual discharge used active-channel width, drainage area and mean annual precipitation as independent variables, with active-channel width being most significant. The equations for 80-percent exceedance discharge and 95-percent exceedance discharge used only active-channel width as an independent variable. The standard error or estimate for the best equation for estimating mean annual discharge was 27 percent. The standard errors of estimate for the equations were 67 percent for estimating 80-percent exceedance discharge and 75 percent for estimating 95-percent exceedance discharge. (USGS)

Water-Resources Investigations Report↗
USGS1984

Floods of May 1978 in southeastern Montana and northeastern Wyoming

Heavy rain and some snow fell on previously saturated ground over southeastern Montana and northeastern Wyoming during May 16-19, 1978. The maximum amount of 7.60 inches within a 72-hour period observed at Lame Deer, Montana, set a record for the month of May in that region. Heavy flooding occurred in the drainages of the Yellowstone River and its tributaries as well as the Belle Fourche, Cheyenne, and North Platte Rivers. The previous maximum flood of record was exceeded at 48 gaged sites, and the 1-percent chance flood was equaled or exceeded at 24 sites. Flood damage was extensive, exceeding $33 million. Nineteen counties in the two States were declared major disaster areas. Mean daily suspended-sediment discharges exceeded previously recorded maximum mean daily values at four sites on the Powder River. The maximum daily suspended-sediment discharge of 2,810,000 tons per day occurred on May 20 at the Site Powder River near Arvada, Wyoming. (USGS)

Professional Paper↗
USGS1983

Mean annual runoff and peak flow estimates based on channel geometry of streams in southeastern Montana

Equations using channel-geometry measurements were developed for estimating mean runoff and peak flows of ungaged streams in southeastern Montana. Two separate sets of esitmating equations were developed for determining mean annual runoff: one for perennial streams and one for ephemeral and intermittent streams. Data from 29 gaged sites on perennial streams and 21 gaged sites on ephemeral and intermittent streams were used in these analyses. Data from 78 gaged sites were used in the peak-flow analyses. Southeastern Montana was divided into three regions and separate multiple-regression equations for each region were developed that relate channel dimensions to peak discharge having recurrence intervals of 2, 5, 10, 25, 50, and 100 years. Channel-geometery relations were developed using measurements of the active-channel width and bankfull width. Active-channel width and bankfull width were the most significant channel features for estimating mean annual runoff for al types of streams. Use of this method requires that onsite measurements be made of channel width. The standard error of estimate for predicting mean annual runoff ranged from about 38 to 79 percent. The standard error of estimate relating active-channel width or bankfull width to peak flow ranged from about 37 to 115 percent. (USGS)

Water-Resources Investigations Report↗
USGS1983

Mean annual runoff and peak flow estimates based on channel geometry of streams in northeastern and western Montana

Equations for estimating mean annual runoff and peak discharge from measurements of channel geometry were developed for western and northeastern Montana. The study area was divided into two regions for the mean annual runoff analysis, and separate multiple-regression equations were developed for each region. The active-channel width was determined to be the most important independent variable in each region. The standard error of estimate for the estimating equation using active-channel width was 61 percent in the Northeast Region and 38 percent in the West region. The study area was divided into six regions for the peak discharge analysis, and multiple regression equations relating channel geometry and basin characteristics to peak discharges having recurrence intervals of 2, 5, 10, 25, 50 and 100 years were developed for each region. The standard errors of estimate for the regression equations using only channel width as an independent variable ranged from 35 to 105 percent. The standard errors improved in four regions as basin characteristics were added to the estimating equations. (USGS)

Water-Resources Investigations Report↗
USGS1983

Flood estimates for ungaged streams in Glacier and Yellowstone National Parks, Montana

Estimates of 100-year discharges were made at 59 sites in Glacier National Park and 21 sites in Yellowstone National Park to assist the National Park Services in quantifying stream inflow and outflow in the Parks. The estimates were made using regression equations previously developed for Montana. The resulting 100-year discharges are listed in tables; the discharges ranged from 260 to 53,200 cu ft/s in Glacier National Park and from 110 to 27,900 cu ft/s in Yellowstone National Park. (USGS)

Montana, Wyoming↗
USGS1982

Floods of May 1981 in west-central Montana

Extensive flooding occurred in west-central Montana during May 22-23, 1981, as a result of a series of rainstorms. Flooding was particularly severe in the communities of East Helena, Belt, and Deer Lodge. Although no lives were lost, total flood damages were estimated by the Montana Disaster Emergency Services Division to be in excess of $30 million. Peak discharges were determined at 75 sites in the flooded area. At 25 sites the May 1981 peak discharge exceeded the computed 100-year frequency flood, and at 29 sites, where previous flow records are available, the May 1981 peak discharge exceeded the previous peak of record. (USGS)

Montana↗
USGS1981

Revised techniques for estimating magnitude and frequency of floods in Montana

Relations for estimating the flood magnitudes for ungaged sites in Montana have been updated. The State was divided into eight regions and separate multiple-regression equations for each region were developed that relate logarithms of annual flood magnitude to logarithms of basin characteristics for exceedance probabilities of 50, 20, 10, 4, 2, and 1 percent. The standard errors of estimate for an exceedance probability of 1 percent ranged from 39 to 58 percent in the western and central parts of the State and from 47 to 83 percent in the eastern part. The standard errors of estimate indicate a substantial improvement over previous studies. Techniques for transferring annual flood-frequency information at gaged sites to ungaged sites on the same stream have been updated. Included are curves relating flood-frequency information to drainage area for eight major streams in the State. Maximum known flood peaks in Montana are compared with estimated 1-percent-chance flood peaks and with national maximum known flood peaks. Values of flood discharges for selected exceedance probabilities and values of significant basin characteristics for all gaging stations used in the analysis are tabulated. Included are data for 339 stations in Montana and 34 nearby stations in Canada and adjoining States. (USGS)

Open-File Report↗