Saturday, 15 July 2006

Measuring Water Table Depth in Loamy Soils with Relic Features.

Edgar Mersiovsky1, Reed Cripps1, Doug Wysocki2, and Cathy Seybold3. (1) USDA-NRCS, USDA-NRCS/Soil Science, 700 W Capitol Ave/Rm 3416 Fed Bldg., Little Rock, AR 72201, (2) NRCS-USDA, 100 Centennial Mall, Lincoln, NE 68508, (3) USDA/NRCS, National Soil Survey Center, Federal Bldg, 100 Centennial Mall North, Lincoln, NE 68508-3866

The USDA-NRCS conducted a study to monitor seasonal water tables in soils within MLRA 131A, Southern Mississippi River Alluvium. Previous studies have suggested that the redoximorphic features in soils within loamy family particle size classes may be relic. Initially, soils along the Mississippi River Meander Belts as mapped by Roger Saucier will be studied. Soils with family particle sizes of fine-loamy, fine-silty, or coarse will be considered. The objective of this study is to collect soil water data for soils and landform positions throughout the Lower Mississippi Valley in a comprehensive and uniform manner. Collected data will be used to assist in populating the NASIS database and to refine interpretations affected by soil water data. The Dundee Series (Fine-silty, mixed, active, thermic Typic Endoaqualfs) will be studied first. Data within NASIS shows that the water table can be within 0.5 foot of the surface. The Official Series Description shows that in drained areas the water table is below 4 feet. Fourteen (14) sites throughout MLRA 131A along the meander belt of the Mississippi River are being monitored. At each site, three (3) piezometers are installed. Automatic Waterlogger-15 units from Global Water are installed in 2-inch PVC pipe. Data is downloaded via computer from each peizometer. The shallowest is installed at the contact with the argillic horizon. This is to see how much of an influence the argillic horizon has with water movement. The second piezometer is placed within the argillic horizon to see if this layer becomes saturated. The third is placed at least 2 millimeters (mm) below the surface. This peizometer will assist in determining how high the water table rises within the soil. Preliminary data along the study area seems to be consistent with previous studies. Data from northern Louisiana indicates that there is water that stays above the argillic horizon for a short period of time after rain events. The data shows that the argillic horizon does not become saturated. The data from the deepest peizometer indicates that the water table may rise to within 3 feet. Preliminary data from other sites also indicate these trends. As more data is collected, this depth will be refined to indicate the water table status in the soil.

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