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Ernest D. Cobb

Publications and source records attributed to Ernest D. Cobb.

14 recordsLinked to original sources
USGS1993

Broad-band acoustic Doppler current profiler

The broad-band acoustic Doppler current profiler is an instrument that determines velocity based on the Doppler principle by reflecting acoustic signals off sediment particles in the water. The instrument is capable of measuring velocity magnitude and direction throughout a water column and of measuring water depth. It is also capable of bottom tracking and can, therefore, keep track of its own relative position as it is moved across a channel. Discharge measurements can be made quickly and, based on limited tests, accurately with this instrument.

Flow Measurement and Instrumentation↗
USGS1986

Fluorometric procedures for dye tracing

This manual describes the current fluorometric procedures used by the U.S. Geological Survey in dye tracer studies such as time of travel, dispersion, reaeration, and dilution-type discharge measurements. The advantages of dye tracing are (1) low detection and measurement limits and (2) simplicity and accuracy in measuring dye tracer concentrations using fluorometric techniques. The manual contains necessary background information about fluorescence, dyes, and fluorometers and a description of fluorometric operation and calibration procedures as a guide for laboratory and field use. The background information should be useful to anyone wishing to experiment with dyes, fluorometer components, or procedures different from those described. In addition, a brief section on aerial photography is included because of its possible use to supplement ground-level fluorometry.

Techniques of Water-Resources Investigations↗
USGS1986

Evaluation of streams in selected communities for the application of limited-detail study methods for flood-insurance studies

The U.S. Geological Survey evaluated 2,349 communities in 1984 for the application of limited-detail flood-insurance study methods, that is, methods with a reduced effort and cost compared to the detailed studies. Limited-detail study methods were found to be appropriate for 1,705 communities, while detailed studies were appropriate for 62 communities and no studies were appropriate for 582 communities. The total length of streams for which limited-detail studies are recommended is 9,327 miles with a corresponding cost of $23,007,000. This results in average estimated costs for conducting limited-detail studies of $2,500 per mile of studied stream length. The purpose of the report is to document the limited-detail study methods and the results of the evaluation. (USGS)

Water-Resources Investigations Report↗
USGS1985

Measurement of discharge using tracers

The development of fluorescent dyes and fluorometers that can measure these dyes at very low concentrations has made dye-dilution methods practical for measuring discharge. These methods are particularly useful for determining discharge under certain flow conditions that are unfavorable for current meter measurements. These include small streams, canals, and pipes where 1. Turbulence is excessive for current-meter measurement but conducive to good mixing. 2. Moving rocks and debris may damage instruments placed in the flow. 3. Cross-sectional areas or velocities are indeterminate or changing. 4. The flow is unsteady, such as the flow that exists with storm-runoff events on small streams and urban storm-sewer systems. 5. The flow is physically inaccessible or unsafe. From a practical standpoint, such methods are limited primarily to small streams, because of the excessively long channel-mixing lengths required for larger streams. Very good accuracy can be obtained provided that 1. Adequate mixing length and time are allowed. 2. Careful field and laboratory techniques are used. 3. Dye losses are not significant. This manual describes the slug-injection and constant-rate injection methods of performing tracer-dilution measurements. Emphasis is on the use of fluorescent dyes as tracers and the equipment, field methods, and laboratory procedures for performing such measurements. The tracer-velocity method is also briefly discussed.

Techniques of Water-Resources Investigations↗
USGS1984

Measurement of discharge using tracers

The development of fluorescent dyes and fluorometers that can measure these dyes at very low concentrations has made dye-dilution methods practical for measuring discharge. These methods are particularly useful for determining discharge under certain flow conditions that are unfavorable for current meter measurements. These include small streams, canals, and pipes where: Turbulence is excessive for current meter measurement but conducive to good mixing. Moving rocks and debris are damaging to any instruments placed in the flow. Cross-sectional areas or velocities are indeterminant or changing. There are some unsteady flows such as exist with storm-runoff events on small streams. The flow is physically inaccessible or unsafe. From a practical standpoint, such measurements are limited primarily to small streams due to excessively long channel mixing lengths required of larger streams. Very good accuracy can be obtained provided: Adequate mixing length and time are allowed. Careful field and laboratory techniques are employed. Dye losses are not significant. This manual describes the slug-injection and constant-rate injection methods of performing tracer-dilution measurements. Emphasis is on the use of fluorescent dyes as tracers and the equipment, field methods, and Laboratory procedures for performing such measurements. The tracer-velocity method is also briefly discussed.

Open-File Report↗
USGS1984

Fluorometric procedures for dye tracing

This manual describes the current fluorometric procedures used by the U.S. Geological Survey in dye tracer studies such as time of travel, dispersion, reaeration, and dilution-type discharge measurements. The outstanding characteristics of dye tracing are: (1) the low detection and measurement limits, and (2) the simplicity and accuracy of measuring dye tracer concentrations using fluorometric techniques. The manual contains necessary background information about fluorescence, dyes, and fluorometers and a description of fluorometric operation and calibration procedures as a general guide for laboratory and field use. The background information should be useful to anyone wishing to experiment with dyes, fluorometer components, or procedures different from those described. In addition, a brief section is included on aerial photography because of its possible use to supplement ground-level fluorometry.

Open-File Report↗
USGS1979

Floods in Puerto Rico, magnitude and frequency

Annual-peak discharge records at 50 sites in Puerto Rico with five or more years of record were used to determine individual site log-Pearson type III frequency curves. The frequency curve values for 2-, 10-, 25-, 50-, and 100-year recurrence intervals at 37 sites with 10 or more years of record were regressed against basin characteristics. Drainage area and mean annual rainfall proved to be the only independent variables significant at the 95 percent confidence level in these regression equations. (Woodard-USGS)

Water-Resources Investigations Report↗
USGS1978

Estimates of 7-day, 10-year minimum flows at selected stream sites in Puerto Rico

The 7-day, 10-year minimum flow of streams is used as an index for determining the capacity of streams to receive waste effluents. This index of flow was computed from streamflow records for 31 stream sites in Puerto Rico. In addition, there was a need for the 7-day, 10-year minimum flow at an additional 15 stream sites for which adequate streamflow data were not available. The flow index was estimated at these sites on the basis of available record, records at nearby sites, and comparisons with drainage areas.

Puerto Rico↗
USGS1971

The national hydrologic bench-mark network

The United States is undergoing a dramatic growth of population and demands on its natural resources. The effects are widespread and often produce significant alterations of the environment. The hydrologic bench-mark network was established to provide data on stream basins which are little affected by these changes. The network is made up of selected stream basins which are not expected to be significantly altered by man. Data obtained from these basins can be used to document natural changes in hydrologic characteristics with time, to provide a better understanding of the hydrologic structure of natural basins, and to provide a comparative base for studying the effects of man on the hydrologic environment. There are 57 bench-mark basins in 37 States. These basins are in areas having a wide variety of climate and topography. The bench-mark basins and the types of data collected in the basins are described.

Circular↗
USGS1969

Movement of a solute in the Potomac River estuary at Washington, D.C., at low inflow conditions

The movement of a solute, as represented by a soluble fluorescent dye, was observed in the Potomac River estuary at Washington, D.C. The average net rate of downstream movement of the solute centroid was less than 0.6 mile per day. The movement of a solute is highly dependent on the nontidal inflow to the estuary. During the study, the average inflow was 900 cubic feet per second a very low value, equaled or exceeded 98 percent of the time. Using a storage equation, the average movement of a solute was estimated for nontidal inflow of 3,100 and 6,500 cubic feet per second; these inflows are equaled or exceeded 75 and 50 percent of the time, respectively. The study showed that tidal action was fairly efficient in dispersing the solute longitudinally. The solute, which was dumped 1,000 feet upstream from the 14th Street Bridge, was observed as far upstream as Roosevelt Island. A transient longitudinal dispersion coefficient at the end of 150 hours was determined to be 210 square feet per second. On the other hand, the lateral diffusion was a slow process and the lateral distribution of the solute was far from uniform at the end of 6½ days after the release.

Washington D.C.↗