Geology topics

G.D. Glysson

Publications and source records attributed to G.D. Glysson.

6 recordsLinked to original sources

USGS2012

A comparison of load estimates using total suspended solids and suspended-sediment concentration data

This paper presents the results to-date from a continuing investigation into the differences between total suspended solids (TSS) and suspended-sediment concentration (SSC) data and the ramifications of using each type of data to estimate sediment loads. It compares estimates of annual suspended-sediment loads that were made using regression equations developed from paired TSS and SSC data, to annual loads computed by the U.S. Geological Survey (USGS) using traditional techniques and SSC data. Load estimates were compared for 10 stations where sufficient TSS and SSC paired data were available to develop sediment-transport curves for the same time period that daily suspended-sediment records were available. Results of these analyses indicate that as the time frame over which the estimates were made increases, the overall errors associated with the estimates decreases with respect to loads computed using traditional USGS techniques. Using SSC data to compute loads tends to produce estimates closer to those computed by traditional techniques than those computed from TSS data. Loads computed from TSS data tend to be negatively biased with respect to those computed by traditional USGS techniques.

Conference Paper↗

USGS2006

User's manual for the Graphical Constituent Loading Analysis System (GCLAS)

This manual describes the Graphical Constituent Loading Analysis System (GCLAS), an interactive cross-platform program for computing the mass (load) and average concentration of a constituent that is transported in stream water over a period of time. GCLAS computes loads as a function of an equal-interval streamflow time series and an equal- or unequal-interval time series of constituent concentrations. The constituent-concentration time series may be composed of measured concentrations or a combination of measured and estimated concentrations. GCLAS is not intended for use in situations where concentration data (or an appropriate surrogate) are collected infrequently or where an appreciable amount of the concentration values are censored. It is assumed that the constituent-concentration time series used by GCLAS adequately represents the true time-varying concentration. Commonly, measured constituent concentrations are collected at a frequency that is less than ideal (from a load-computation standpoint), so estimated concentrations must be inserted in the time series to better approximate the expected chemograph. GCLAS provides tools to facilitate estimation and entry of instantaneous concentrations for that purpose. Water-quality samples collected for load computation frequently are collected in a single vertical or at single point in a stream cross section. Several factors, some of which may vary as a function of time and (or) streamflow, can affect whether the sample concentrations are representative of the mean concentration in the cross section. GCLAS provides tools to aid the analyst in assessing whether concentrations in samples collected in a single vertical or at single point in a stream cross section exhibit systematic bias with respect to the mean concentrations. In cases where bias is evident, the analyst can construct coefficient relations in GCLAS to reduce or eliminate the observed bias. GCLAS can export load and concentration data in formats suitable for entry into the U.S. Geological Survey's National Water Information System. GCLAS can also import and export data in formats that are compatible with various commonly used spreadsheet and statistics programs.

Techniques and Methods↗

USGS2001

GCLAS: a graphical constituent loading analysis system

The U. S. Geological Survey has developed a program called GCLAS (Graphical Constituent Loading Analysis System) to aid in the computation of daily constituent loads transported in stream flow. Due to the relative paucity with which most water-quality data are collected, computation of daily constituent loads is moderately to highly dependent on human interpretation of the relation between stream hydraulics and constituent transport. GCLAS provides a visual environment for evaluating the relation between hydraulic and other covariate time series and the constituent chemograph. GCLAS replaces the computer program Sedcalc, which is the most recent USGS sanctioned tool for constructing sediment chemographs and computing suspended-sediment loads. Written in a portable language, GCLAS has an interactive graphical interface that permits easy entry of estimated values and provides new tools to aid in making those estimates. The use of a portable language for program development imparts a degree of computer platform independence that was difficult to obtain in the past, making implementation more straightforward within the USGS' s diverse computing environment. Some of the improvements introduced in GCLAS include (1) the ability to directly handle periods of zero or reverse flow, (2) the ability to analyze and apply coefficient adjustments to concentrations as a function of time, streamflow, or both, (3) the ability to compute discharges of constituents other than suspended sediment, (4) the ability to easily view data related to the chemograph at different levels of detail, and (5) the ability to readily display covariate time series data to provide enhanced visual cues for drawing the constituent chemograph.

Conference Paper↗

USGS2000

Comparability of suspended-sediment concentration and total suspended solids data

Two laboratory analytical methods — suspended-sediment concentration (SSC) and total suspended solids (TSS) — are predominantly used to quantify concentrations of suspended solid-phase material in surface waters of the United States. The analytical methods differ. SSC data are produced by measuring the dry weight of all the sediment from a known volume of a water-sediment mixture. TSS data are produced by several methods, most of which entail measuring the dry weight of sediment from a known volume of a subsample of the original. An evaluation of 3,235 paired SSC and TSS data, of which 860 SSC values include percentages of sand-size material, shows bias in the relation between SSC and TSS —SSC values tend to increase at a greater rate than their corresponding paired TSS values. As sand-size material in samples exceeds about a quarter of the sediment dry weight, SSC values tend to exceed their corresponding paired TSS values. TSS analyses of three sets of quality-control samples (35 samples) showed unexpectedly small sediment recoveries and relatively large variances in the TSS data. Two quality-control data sets (18 samples) that were analyzed for SSC showed both slightly deficient sediment recoveries, and variances that are characteristic of most other quality-control data compiled as part of the U.S. Geological Survey’s National Sediment Laboratory Quality Assurance Program. The method for determining TSS, which was originally designed for analyses of wastewater samples, is shown to be fundamentally unreliable for the analysis of natural-water samples. In contrast, the method for determining SSC produces relatively reliable results for samples of natural water, regardless of the amount or percentage of sand-size material in the samples. SSC and TSS data collected from natural water are not comparable and should not be used interchangeably. The accuracy and comparability of suspended solid-phase concentrations of the Nation’s natural waters would be greatly enhanced if all these data were produced by the SSC analytical method.

Water-Resources Investigations Report↗

USGS1993

Quality assurance plan for the collection and processing of sediment data by the U.S. Geological Survey, Water Resources Division

The U.S. Geological Survey sediment data quality assurance plan identifies and explains required quality assurance and suggested quality control practices. The approach is to subdivide the process for obtaining sediment data into 3 parts: (1) field, (2) office, and (3) laboratory operations. The report also summarizes recommended goals for each subcategory. The quality assurance and quality control practices are described by stating the minimum acceptable activities that a district should conduct. For example, the plan describes field calibration of thermometers and standards used to calibrate a thermometer. The plan also proposes corrective actions if the quality control procedures identify a problem. The plan describes the formal reports prepared by a district that describe the completeness of sediment data and presents an evaluation of data obtained by the quality assurance program. Also described in the plan are the external (non-district) reviews that are needed to examine district sediment operations for conformity with district quality assurance plans and national quality assurance programs.

Open-File Report↗

USGS1976

Redwood National Park studies; data release number 2, Redwood Creek, Humboldt County, and Mill Creek, Del Norte County, California, April 11, 1974-September 30, 1975

An interdisciplinary study has been undertaken in Redwood National Park, Calif., to describe parts of the ecosystems and recent changes in the intensity of erosion and sedimentation, define processes that may alter the natural ecosystems, and assess the impact of recent road construction and timber harvest. This report is the second of a series that will present data collected in this study. Stream-discharge and water-quality data were collected at 53 sampling stations in the Redwood Creek and Mill Creek drainage basins. Measurements included the following variables: Stream stage and discharge; turbidity; sediment; onsite water-quality determinations of temperature, pH , total alkalinity, specific conductance, and dissolved-oxxygen concentration; chemical analyses of water samples for major dissolved solids, selected trace elements, nitrogen, phosphorus, and organic carbon; chemical analyses of bottom sediment for organic carbon and pesticides; bacteria; benthic invertebrates; fish; periphyton; phytoplankton; and seston. Additional data include changes in geometry at 10 stream-channel cross sections along Mill Creek and the distribution of erosional landforms in the Mill Creek drainage basin; quantity and chemical composition of rainwater; and the intragravel-streambed condition at selected stations in the Redwood Creek drainage basin. (Woodard-USGS)

Open-File Report↗