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Geology topics

Gary D. Tasker

Publications and source records attributed to Gary D. Tasker.

At least 55 records · Page 3Linked to original sources
USGS1990

Simulated effects of climatic change on runoff and drought in the Delaware River Basin

Various projection of climatic change were applied to watershed models of the Delaware River basin. Simulations indicate that a warming could reduce annual runoff by as much as 25 percent if current precipitation patterns continue. Simulations indicate that the largest changes in basin drought are in response to relatively small changes in precipitation. Basin drought was less sensitive to increases in temperature, reservoir capacity, ground-water pumpage during drought, and consumptive water use--in that order of importance. The effects of global warming on basin runoff and drought cannot be determined precisely, as yet, principally because of the unreliability of precipitation projections.

Conference Paper↗
USGS1990

Some hydrological impacts of climate change for the Delaware River Basin

To gain insight into possible impacts of climate change on water availability in the Delaware River, two models are linked. The first model is a monthly water balance model that converts the temperature and precipitation values generated by a random number generator to monthly streamflow values. The monthly streamflow values are input to a second model that simulates the operation of reservoirs and diversions within the basin. The output for the two linked models consists of time series of reservoir levels and streamflow at key points in the basin. Model results for a base case, in which monthly temperature and precipitation statistics are unchanged from historical records, are compared to several changed-climate scenarios under a standard set of rules of operation.

Conference Paper↗
USGS1989

An operational GLS model for hydrologic regression

Recent Monte Carlo studies have documented the value of generalized least squares (GLS) procedures to estimate empirical relationships between streamflow statistics and physiographic basin characteristics. This paper presents a number of extensions of the GLS method that deal with realities and complexities of regional hydrologic data sets that were not addressed in the simulation studies. These extensions include: (1) a more realistic model of the underlying model errors; (2) smoothed estimates of cross correlation of flows; (3) procedures for including historical flow data; (4) diagnostic statistics describing leverage and influence for GLS regression; and (5) the formulation of a mathematical program for evaluating future gaging activities.

Journal of Hydrology↗
USGS1988

Estimation of urban stormwater quality

Two data-based methods for estimating urban stormwater quality have recently been made available - a planning level method developed by the U.S. Environmental Protection Agency (EPA), and a nationwide regression method developed by the U.S. Geological Survey. Each method uses urban stormwater water-quality constituent data collected for the Nationwide Urban Runoff Program (NURP) during 1979-83. The constituents analyzed include 10 chemical constituents - chemical oxygen demand (COD), total suspended solids (TSS), dissolved solids (DS), total nitrogen (TN), total ammonia plus nitrogen (AN), total phosphorus (TP), dissolved phosphorous (DP), total copper (CU), total lead (PB), and total zinc (ZN). The purpose of this report is to briefly compare features of the two estimation methods.

Conference Paper↗
USGS1987

Regional regression of flood characteristics employing historical information

Streamflow gauging networks provide hydrologic information for use in estimating the parameters of regional regression models. The regional regression models can be used to estimate flood statistics, such as the 100 yr peak, at ungauged sites as functions of drainage basin characteristics. A recent innovation in regional regression is the use of a generalized least squares (GLS) estimator that accounts for unequal station record lengths and sample cross correlation among the flows. However, this technique does not account for historical flood information. A method is proposed here to adjust this generalized least squares estimator to account for possible information about historical floods available at some stations in a region. The historical information is assumed to be in the form of observations of all peaks above a threshold during a long period outside the systematic record period. A Monte Carlo simulation experiment was performed to compare the GLS estimator adjusted for historical floods with the unadjusted GLS estimator and the ordinary least squares estimator. Results indicate that using the GLS estimator adjusted for historical information significantly improves the regression model.

Journal of Hydrology↗
USGS1987

Analysis of surface-water data network in Kansas for effectiveness in providing regional streamflow information; with a section on theory and application of generalized least squares

This report documents the results of an analysis of the surface-water data network in Kansas for its effectiveness in providing regional streamflow information. The network was analyzed using generalized least squares regression. The correlation and time-sampling error of the streamflow characteristic are considered in the generalized least squares method. Unregulated medium-, low-, and high-flow characteristics were selected to be representative of the regional information that can be obtained from streamflow-gaging-station records for use in evaluating the effectiveness of continuing the present network stations, discontinuing some stations, and (or) adding new stations. The analysis used streamflow records for all currently operated stations that were not affected by regulation and for discontinued stations for which unregulated flow characteristics, as well as physical and climatic characteristics, were available. The State was divided into three network areas, western, northeastern, and southeastern Kansas, and analysis was made for the three streamflow characteristics in each area, using three planning horizons. The analysis showed that the maximum reduction of sampling mean-square error for each cost level could be obtained by adding new stations and discontinuing some current network stations. Large reductions in sampling mean-square error for low-flow information could be achieved in all three network areas, the reduction in western Kansas being the most dramatic. The addition of new stations would be most beneficial for mean-flow information in western Kansas. The reduction of sampling mean-square error for high-flow information would benefit most from the addition of new stations in western Kansas. Southeastern Kansas showed the smallest error reduction in high-flow information. A comparison among all three network areas indicated that funding resources could be most effectively used by discontinuing more stations in northeastern and southeastern Kansas and establishing more new stations in western Kansas.

Water Supply Paper↗
USGS1985

Analysis of surface-water data network in Kansas for effectiveness in providing regional streamflow information

The surface water data network in Kansas was analyzed using generalized least squares regression for its effectiveness in providing regional streamflow information. The correlation and time-sampling error of the streamflow characteristic are considered in the generalized least squares method. Unregulated medium-flow, low-flow and high-flow characteristics were selected to be representative of the regional information that can be obtained from streamflow gaging station records for use in evaluating the effectiveness of continuing the present network stations, discontinuing some stations; and/or adding new stations. The analysis used streamflow records for all currently operated stations that were not affected by regulation and discontinued stations for which unregulated flow characteristics, as well as physical and climatic characteristics, were available. The state was divided into three network areas, western, northeastern, and southeastern Kansas, and analysis was made for three streamflow characteristics in each area, using three planning horizons. The analysis showed that the maximum reduction of sampling mean square error for each cost level could be obtained by adding new stations and discontinuing some of the present network stations. Large reductions in sampling mean square error for low-flow information could be accomplished in all three network areas, with western Kansas having the most dramatic reduction. The addition of new stations would be most beneficial for man-flow information in western Kansas, and to lesser degrees in the other two areas. The reduction of sampling mean square error for high-flow information would benefit most from the addition of new stations in western Kansas, and the effect diminishes to lesser degrees in the other two areas. Southeastern Kansas showed the smallest error reduction in high-flow information. A comparison among all three network areas indicated that funding resources could be most effectively used by discontinuing more stations in northeastern and southeastern Kansas and establishing more new stations in western Kansas. (Author's abstract)

Kansas↗
USGS1984

Cost effectiveness of the stream-gaging program in northeastern California

Results are documented of a study of the cost effectiveness of the stream-gaging program in northeastern California. Data uses and funding sources were identified for the 127 continuous stream gages currently being operated in the study area. One stream gage was found to have insufficient data use to warrant cooperative Federal funding. Flow-routing and multiple-regression models were used to simulate flows at selected gaging stations. The models may be sufficiently accurate to replace two of the stations. The average standard error of estimate of streamflow records is 12.9 percent. This overall level of accuracy could be reduced to 12.0 percent using computer-recommended service routes and visit frequencies. (USGS)

Water-Resources Investigations Report↗
USGS1983

Effective record length for the T-year event

The effect of serial dependence on the reliability of an estimate of the T -yr. event is of importance in hydrology because design decisions are based upon the estimate. In this paper the reliability of estimates of the T -yr. event from two common distributions is given as a function of number of observations and lag-one serial correlation coefficient for T = 2, 10, 20, 50, and 100 yr. A lag-one autoregressive model is assumed with either a normal or Pearson Type-III disturbance term. Results indicate that, if observations are serially correlated, the effective record length should be used to estimate the discharge associated with the expected exceedance probability.

Journal of Hydrology↗
USGS1982

Estimating peak flow characteristics at ungaged sites by ridge regression

A regression simulation model, is combined with a multisite streamflow generator to simulate a regional regression of 50-year peak discharge against a set of basin characteristics. Monte Carlo experiments are used to compare the unbiased ordinary lease squares parameter estimator with Hoerl and Kennard's (1970a) ridge estimator in which the biasing parameter is that proposed by Hoerl, Kennard, and Baldwin (1975). The simulation results indicate a substantial improvement in parameter estimation using ridge regression when the correlation between basin characteristics is more than about 0.90. In addition, results indicate a strong potential for improving the mean square error of prediction of a peak-flow characteristic versus basin characteristics regression model when the basin characteristics are approximately colinear. The simulation covers a range of regression parameters, streamflow statistics, and basin characteristics commonly found in regional regression studies.

Open-File Report↗
USGS1982

Design of surface-water data networks for regional information

This report describes a technique, Network Analysis of Regional Information (NARI), and the existing computer procedures that have been developed for the specification of the regional information-cost relation for several statistical parameters of streamflow. The measure of information used is the true standard error of estimate of a regional logarithmic regression. The cost is a function of the number of stations at which hydrologic data are collected and the number of years for which the data are collected. The technique can be used to obtain either (1) a minimum cost network that will attain a prespecified accuracy and reliability or (2) a network that maximizes information given a set of budgetary and time constraints.

Water Supply Paper↗
USGS1977

Hydrologic data of the coastal drainage basins of southeastern Massachusetts, Plymouth to Weweantic River, Wareham

The principal basins in this study in southeastern Massachusetts are those of Town Brook, Eel River, and Beaverdam Brook, all draining to Cape Cod Bay; Herring Brook draining to the Cape Cod Canal; and Red Brook, Agawam River, Wankinco River, and Weweantic River, all draining to Buzzards Bay. This report presents, in tabular form, selected records of wells, test wells , borings, and important springs; measurements of stream discharge, specific conductance, and temperature at partial-record stations; chemical analyses of ground water and surface water; and a summary of municipal water sources and additional sources available. The data were collected from 1969 to 1971 in cooperation with the Massachusetts Water Resources Commission. (Woodard-USGS)

Open-File Report↗
USGS1975

Hydrologic data of the coastal drainage basins of southeastern Massachusetts, Weir River, Hingham, to Jonas River, Kingston

The principal basins are those of Weir River, James Brook, Bound Brook, North River, South River, and Jones River, all draining to Massachusetts Bay and Cape Cod Bay. These basins are bounded on the north by the Weymouth River basins, on the west by the Taunton River basin, and on the south by small basins that drain to Cape Cod Bay. The basins included all, or parts of, the Norwell, Pembroke, Plymouth, Plympton, Rockland, Scituate, Weymouth, and Whitman. With the following exceptions, each town is served by its own municipal water system--Hingham and northwest Cohasset by the Hingham Water Company; Abington and Rockland by the Abington-Rockland Joint Water Works; and Plympton lacks a public water supply. Weymouth and Cohasset are in Norfolk County; the other towns are in Plymouth County. This report presents, in tabular form, selected records of wells, test wells, borings, and springs; measurements of stream discharge, specific conductance, and temperature at partial-record stations; chemical analyses of ground water and surface water; and a summary of municipal water sources and additional sources available. The data were collected during a study of the drainage basins from 1969 to 1971 in cooperation with the Massachusetts Water Resources Commission. The report is released in order to make available to the public and to local, state, and federal agencies basic hydrologic information that may aid in planning water-resources development. Basic records contained in this report and streamflow data published elsewhere (U.S. Geol. Survey, 1960 et seq.) complement an interpretive report (Williams and Tasker, 1974).

Massachusetts↗