Hydrogeologic assessment of the Brazos River alluvial aquifer : Waco to Marlin, Texas.

The Brazos River alluvial aquifer is a shallow unconfined aquifer within the alluvial deposits along the Brazos River. The deposits include the floodplain and terrace material which are comprised of clay, silt, sand, and gravel. Thicknesses of the alluvial deposits range up to 80 feet. Groundwater in the terraces is restricted to domestic and livestock wells producing less than 50 gpm. Irrigation wells located in the floodplain may occasionally exceed 800 gpm. Flow directions in the terraces are toward the nearest stream dissection. Flow in the floodplain is toward the Brazos River and slightly downstream. Recharge to the aquifers consists primarily of rainfall recharging the terrace and floodplain surfaces as well as subsurface lateral inflow and recharge from losing streams and surface water bodies. Terrace deposits form minor aquifers that influence the hydrogeology of the floodplain aquifer system. Analysis of the water budget for the study area indicates that a portion of the Brazos River recharge originates from the terrace deposits. This recharge is transmitted through the Lower Taylor Marl Formation, the primary bedrock unit in the area, as lateral recharge into the adjacent floodplain aquifer. Estimates of hydraulic conductivities for the Lower Taylor Marl, as determined from this study, range from 1.45 x 10^-7 to 5.52 x 10^-7 cm/s. Hydrochemical analysis indicates that the groundwater in the Brazos River alluvial aquifer is primarily a calcium bicarbonate water. There is, however, significant variation within the study area. Analysis of chemical data by numerous methods indicate that although there are some trends within the study area, there are no mappable groundwater facies. Statistical analysis of a selected sample set indicate that there are significantly higher concentrations of some ions in the floodplain aquifer than in the terrace systems. Variations in measured parameters are a function of recharge-discharge relationships, flow paths, residence time and mineralogic differences in the aquifer matrix. A two-dimensional flow model is presented that describes the hydrochemical evolution in the aquifer.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Masters

Grantor

Baylor University.

Year dc:date.issued

1990

Author dc:creator

• Harlan, Scott K.

Advisor dc:contributor.advisor

• Yelderman, Joe C.

• Hydrogeology.
• Aquifers -- Texas.
• Geology -- Texas -- McLennan County.
• Geology -- Texas -- Falls County.
• Brazos River Alluvial Aquifer (Tex.)

Statement dc:rights

• Baylor University works are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. Contact libraryquestions@baylor.edu for inquiries about permission.

Language dc:language.iso

en

Handle dc:identifier.uri

https://hdl.handle.net/2104/13048

OAI identifier oai:identifier

oai:baylor-ir.tdl.org:2104/13048