Browsing by Author "Holley, Edward R."
Now showing 1 - 3 of 3
- Results Per Page
- Sort Options
Item Preliminary Investigation of Tracer Gas Reaeration Method for Shallow Bays(Texas Water Resources Institute, 1987-08) Holley, Edward R.; Baker, Sarah H.Accurate estimates of surface exchange rates for volatile pollutants in bays are needed to allow predictions of pollutant movement and retention time. The same types of estimates can be used to calculate reaeration rates. The tracer gas technique has been used to measure surface gas transfer rates in rivers, and to a lesser extent, in estuaries. Application of the technique to bays would be extremely useful, but it is complicated by differences in the hydrodynamics and the density stratification that can exist due to fresh river water overriding heavier saline ocean water. The objective of this research has been to investigate field procedures for application of the tracer gas technique to shallow bays. The modified tracer technique was used with propane for the tracer gas and Rhodamine-WT, a fluorescent dye, for the "conservative" tracer. The propane was injected through porous tile diffusers, and the dye was released simultaneously. The propane acts as a model for the surface exchange of other gases and volatile compounds. Three four-day field trips to Lavaca Bay on the Texas coast of the Gulf of Mexico were made during the course of the study. A variety of experimental techniques was investigated. One was to make a short-duration injection (10-30 minutes) and sample the dye cloud as it moved through the bay. Another was to use a long-duration injection (3 to 4 hours) to obtain quasi-steady conditions. The long injections were discontinued because there appeared to be no practical method of determining the travel time for the samples taken from the tracer plume. Drogues (floats) which are normally used for this purpose consistently drifted downwind from the tracer plumes. Pulses of a second fluorescent dye for determining time of travel became too diffuse to be used for this purpose. The most promising method appears to be the short-duration injection method with a large pulse of the second dye released during the injection to mark the middle of the tracer cloud. A special injection device was designed to prevent mixing of the tracers with heavier saline water near the bed of the bay during injection. A field fluorometer was used both in the field to track the tracer cloud and in the laboratory to measure dye concentrations in the field samples. Propane concentrations were determined with gas chromatography. The same equipment was used to perform laboratory studies to test performance of the equipment in the field and to aid in understanding field test results. These were apparently the first tests to be performed using the tracer gas technique in bays. As a result, the emphasis was on the development of techniques rather than on obtaining data. It appears that workable techniques have been developed, but they now need to be tested under a variety of conditions. Also, the preliminary results which were obtained for gas transfer coefficients indicate some anomalous results. After the completion of the project, it was learned that the addition of formalin to the field tracer gas samples may be affecting the samples adversely. Thus, some laboratory tests are now needed to investigate the behavior of tracer gases in bay water. In summary, the method appears to be very promising, but some additional developmental work is required before it can be used on a routine basisItem Sediment Transport in the Lower Guadalupe and San Antonio Rivers(Texas Water Resources Institute, 1992-01) Holley, Edward R.Texas law requires that fresh water inflows into coastal regions be maintained at adequate levels for an ecologically sound environment; however, very limited data are available on the relation between river flow and sediment transport to coastal regions. This study was undertaken to analyze existing data and to collect field data for the lower part of the Guadalupe River and the San Antonio River. The primary sampling locations were at the U. S. Highway 59 bridges in Victoria for the Guadalupe River and in Goliad for the San Antonio River. No existing data on bedload transport were located. The first part of the analysis of existing data therefore centered on possible correlations of suspended sediment concentrations with simultaneous flow rate, with flow rates which occurred before the sediment concentrations were measured, with particle fall velocity, and with the phase of the hydrograph when the sediment samples were collected. The primary correlation was between the concentration and the simultaneous river flow rate. Even though there is a large amount of scatter in this correlation, none of the other variables was important enough for all of the data to provide any reduction in the scatter. The second part of the analysis of existing data related to which percentage of the flows carries which percentage of the suspended sediment. This analysis confirmed the conventional wisdom that the large majority of the suspended sediment is carried by the infrequent large flows. Because of the very low flows which existed during most of the project period, somewhat more emphasis than originally planned had to be placed on the analysis of existing data. Nevertheless, several sets of field data were collected. A pumping sampling system was tested in order to provide enough sediment for grain size analysis. The concentrations of the pumped samples compared favorably with the traditional P-61 sampling technique. Therefore, this system was used for some of the samples. A few bedload samples were collected; Very limited data indicated that the bedload transport rates are much smaller than the suspended load transport rates. The two largest sets of data were collected on the Guadalupe River at Victoria in April 1990 and on the San Antonio River at Goliad in July 1990. The grain size distributions for various phases of the hydrographs showed very little variations, and there were also very small differences in the suspended grain sizes for the Guadalupe and San Antonio Rivers. For the particular events sampled during these two Held trips, there appeared to be a good correlation between the flow rate and the sediment concentration for the test on the Guadalupe River while there was clearly a significant lag between the flow hydrograph and the suspended sediment hydrograph for the San Antonio River.Item Suspended Sediment Yield in Texas Watersheds(Center for Research in Water Resources, The University of Texas at Austin, 2009-12-03T22:30:47Z) Coonrod, Julia E. Allred; Holley, Edward R.; Maidment, David R.; Ward, George H.