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H.E. Jobson

Publications and source records attributed to H.E. Jobson.

10 recordsLinked to original sources
USGS2001

Simulation of stream discharge and transport of nitrate and selected herbicides in the Mississippi River Basin

Stream discharge and the transport of nitrate, atrazine, and metolachlor in the Mississippi River Basin were simulated using the DAFLOW/BLTM hydrologic model. The simulated domain for stream discharge included river reaches downstream from the following stations in the National Stream Quality Accounting Network: Mississippi River at Clinton, IA; Missouri River at Hermann, MO: Ohio River at Grand Chain, IL: And Arkansas River at Little Rock, AR. Coefficients of hydraulic geometry were calibrated using data from water year 1996; the model was validated by favourable simulation of observed discharges in water years 1992-1994. The transport of nitrate, atrazine, and metolachlor was simulated downstream from the Mississippi River at Thebes, IL, and the Ohio River at Grand Chain. Simulated concentrations compared favourably with observed concentrations at Baton Rouge, LA. Development of this model is a preliminary step in gaining a more quantitative understanding of the sources and fate of nutrients and pesticides delivered from the Mississippi River Basin to the Gulf of Mexico.

Hydrological Processes↗
USGS2001

Predicting river travel time from hydraulic characteristics

Predicting the effect of a pollutant spill on downstream water quality is primarily dependent on the water velocity, longitudinal mixing, and chemical/physical reactions. Of these, velocity is the most important and difficult to predict. This paper provides guidance on extrapolating travel-time information from one within bank discharge to another. In many cases, a time series of discharge (such as provided by a U.S. Geological Survey stream gauge) will provide an excellent basis for this extrapolation. Otherwise, the accuracy of a travel time extrapolation based on a resistance equation can be greatly improved by assuming the total flow area is composed of two parts, an active and an inactive area. For 60 reaches of 12 rivers with slopes greater than about 0.0002, travel times could be predicted to within about 10% by computing the active flow area using the Manning equation with n = 0.035 and assuming a constant inactive area for each reach. The predicted travel times were not very sensitive to the assumed values of bed slope or channel width.

Journal of Hydraulic Engineering↗
USGS1997

Predicting travel time and dispersion in rivers and streams

The possibility of a contaminant being accidentally or intentionally spilled in a river is a constant concern to those using the water. Methods are developed to estimate: (1) the velocity of a contaminant in a river; (2) the rate of attenuation of the peak concentration of a conservative contaminant; and (3) the time required for a contaminant plume to pass a point. The methods are based on data collected by the U.S. Geological Survey in almost a hundred different rivers representing a wide range of sizes, slopes, and geomorphic types. Although the accuracy of the predictions can be greatly increased by performing time-of-travel studies, the emphasis of this paper is on providing methods for making estimates where few data are available. It is shown that the unit-peak concentration is well correlated with travel time and that the travel time of the leading edge averages 89% of the travel time of the peak concentration.

Journal of Hydraulic Engineering↗
USGS1993

Laboratory procedures and data reduction techniques to determine rheologic properties of mass flows

Determining the rheologic properties of coarse- grained mass flows is an important step to mathematically simulate potential inundation zones. Using the vertically rotating flume designed and built by the U.S. Geological Survey, laboratory procedures and subsequent data reduction have been developed to estimate shear stresses and strain rates of various flow materials. Although direct measurement of shear stress and strain rate currently (1992) are not possible in the vertically rotating flume, methods were derived to estimate these values from measurements of flow geometry, surface velocity, and flume velocity.

Water-Resources Investigations Report↗
USGS1987

Langrangian model of nitrogen kinetics in the Chattahoochee River

A Lagrangian reference frame is used to solve the convection‐dispersion equation and interpret water‐quality data obtained from the Chattahoochee River. The model was calibrated using unsteady concentrations of organic nitrogen, ammonia, and nitrite plus nitrate obtained during June 1977 and verified using data obtained during August 1976. Reaction kinetics of the cascade type are shown to provide a reasonable description of the nitrogenspecies processes in the Chattahoochee River. The conceptual model is easy to visualize in the physical sense and the output includes information that is not easily determined from an Eulerian approach, but which is very helpful in model calibration and data interpretation. For example, the model output allows one to determine which data are of most value in model calibration or verification.

Journal of Environmental Engineering↗
USGS1986

Programmers manual for a one-dimensional Lagrangian transport model

A one-dimensional Lagrangian transport model for simulating water-quality constituents such as temperature, dissolved oxygen , and suspended sediment in rivers is presented in this Programmers Manual. Lagrangian transport modeling techniques, the model 's subroutines, and the user-written decay-coefficient subroutine are discussed in detail. Appendices list the program codes. The Programmers Manual is intended for the model user who needs to modify code either to adapt the model to a particular need or to use reaction kinetics not provided with the model. (Author 's abstract)

Water-Resources Investigations Report↗
USGS1986

Users manual for a one-dimensional Lagrangian transport model

A Users Manual for the Lagrangian Transport Model (LTM) is presented. The LTM uses Lagrangian calculations that are based on a reference frame moving with the river flow. The Lagrangian reference frame eliminates the need to numerically solve the convective term of the convection-diffusion equation and provides significant numerical advantages over the more commonly used Eulerian reference frame. When properly applied, the LTM can simulate riverine transport and decay processes within the accuracy required by most water quality studies. The LTM is applicable to steady or unsteady one-dimensional unidirectional flows in fixed channels with tributary and lateral inflows. Application of the LTM is relatively simple and optional capabilities improve the model 's convenience. Appendices give file formats and three example LTM applications that include the incorporation of the QUAL II water quality model 's reaction kinetics into the LTM. (Author 's abstract)

Water-Resources Investigations Report↗