| Popis: |
During June 2002, water levels in the Chicot aquifer system were more than 12.1 meters (40 feet) below the National Geodetic Vertical Datum of 1929 (NGVD 29) in parts of Acadia, Calcasieu, Evangeline, and Jefferson Davis Parishes, in an area that generally coincides with rice-farming areas. During January 2003, water levels were more than 9.1 meters (30 feet) below NGVD 29 in these areas. From June 2002 to January 2003, water levels generally recovered between 1.5 and 6.1 meters (5 and 20 feet) in the Chicot aquifer system in most of Acadia and Jefferson Davis Parishes, southeastern Calcasieu Parish, and southern Evangeline Parish, in an area that generally coincides with rice-farming areas. These water-level changes are representative of the areal extent and magnitude of typical seasonal water-level fluctuations that occur in the aquifer system in response to seasonal ground-water withdrawals for rice irrigation. Near the outcrop area, specific conductance values in the Chicot aquifer system generally are less than 150 uS/cm (microsiemens per centimeter at 25 degrees Celsius). Specific conductance values increase south and east of the outcrop area. Specific conductance values generally range from 151 to 500 uS/cm in rice-farming areas of northwestern Acadia Parish, southeastern Allen Parish, western Evangeline Parish, and northern and central Jefferson Davis Parish. Specific conductance values generally range from 501 to 1,000 uS/cm in most of the remaining rice-farming areas. Specific conductance values often exceed 1,000 uS/cm in an area along the border between Calcasieu and Jefferson Davis Parishes near Iowa, Louisiana, parts of northeastern Cameron Parish, an area of northwestern and central St. Landry Parish; parts of Vermilion Parish, and several areas along the eastern boundary of the study area where the Chicot aquifer system merges with the Atchafalaya aquifer. Specific conductance was measured hourly during pumping at two irrigation wells between 2000 and 2003. Specific conductance values were greater than 1,000 uS/cm in both wells, indicating the presence of saltwater near the wells. Specific conductance values generally fluctuated about 150 uS/cm at both wells, but no long-term trends in the specific conductance were evident in either well. |
