Evaluation and simulation of non-point source agricultural chemical transport in variably saturated soil medium /
A variety of agricultural chemicals are used for crop production. The use of these chemicals causes environmental concerns by the public. Therefore, the fate of agricultural chemicals released to the environment needs to be determined. Computer models that simulate the movement of agricultural chemi...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1996.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=739363311&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | A variety of agricultural chemicals are used for crop production. The use of these chemicals causes environmental concerns by the public. Therefore, the fate of agricultural chemicals released to the environment needs to be determined. Computer models that simulate the movement of agricultural chemicals can be utilized to assess the environmental impact of crop production. However, model simulations require field data for validation and calibration. Therefore, a field research project investigating the fate of agricultural chemicals applied to river floodplains was conducted at the Texas A&M University Research Site on the Brazos River. The research site was instrumented to monitor groundwater flow, surface runoff and weather conditions. The transport of nitrogen and arazine in the soil, surface runoff, groundwater and river was monitored throughout the corn crop growing seasons of 1994 and 1995. From April, 1994 through August, 1995, 185 soil samples, 526 surface runoff samples, 412 groundwater samples and 13 river water samples were obtained. All samples were analyzed for nitrate and atrazine concentrations. Direct interaction between the floodplain aquifer and river was noticed during the field study. The water levels in the aquifer ' were influenced by the river stage fluctuations. A two dimensional, finite difference groundwater computer model, VS2DT (Variably Saturated Two Dimensional Transport Model) was used to simulate groundwater flow and atrazine transport. The entire domain, which consists of soil layers with different soil properties, was decoupled and was simulated separately. The surface clay was decoupled from the sand and gravel aquifer. Macropores were conceptualized in the clay soil flow domain to simulate rapid movement of groundwater and atrazine to the sand and gravel aquifer. Conceptualized macropores, characterized by high hydraulic conductivity and low porosity, were incorporated in the model to simulate the field conditions. The computer model effectively simulated groundwater flow resulting a satisfactory match between the simulated and measured water table elevations. The numerical simulations effectively characterized the hydraulic interaction between the river and alluvium. Extensive field studies conducted at the site contributed to a groundwater database which can be used to validate models in this area of research. |
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| Item Description: | Vita. "Major Subject: Agricultural Engineering". |
| Physical Description: | xxii, 191 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references: pages 143-149. |