Discharge of herbicides from the Mississippi River Basin to the Gulf of Mexico, 1991-97
No abstract available.
Mississippi River basin↗
Geology topics
Research about Mississippi River basin
Source-linked reports with geographic coverage including Mississippi River basin.
Effects of the 1993 flood on the determination of flood magnitude and frequency in Iowa - Floods in the upper Mississippi River basin 1993
To evaluate the effects of the 1993 flood in the upper Mississippi River Basin on the determination of flood magnitude and frequency, discharges that had recurrence intervals of 10, 25, 50, and 100 years computed from data through the 1992 water year were compared with those computed from data through the 1993 water year for 62 selected streamflow-gaging stations in Iowa. On the basis of the flood-frequency analysis computed from data through the 1993 water year, a flood that was greater than or equal to a 10-year recurrence interval discharge occurred during 1993 at all 62 gaging stations, and a flood greater than or equal to a 100-year recurrence-interval discharge occurred at 11 of the gaging stations. Results of the comparison indicated that inclusion of the 1993 flood in the data base resulted in an increase in the magnitude of dis charges for all selected recurrence intervals at the 62 streamflow-gaging stations in Iowa. A larger percentage increase in the magnitude of discharge was computed for the larger recurrence intervals than for the smaller recurrence intervals for most of the selected gaging stations . As a result of including the 1993 peak discharge in the flood-frequency analysis, three gaging stations had an increase in the 100-year recurrence-interval discharge that was greater than 30 percent. Several factors, which included recurrence intervals for the 1993 peak discharges and the effective record lengths for 1993, were investigated for the 62 selected streamflow-gaging stations to evaluate their possible effect on the computed flood-frequency discharges. The combined effect of these two factors on the computed 100-year recurrence-interval discharges was significant. Gaging stations were grouped into four discrete categories on the basis of recurrence intervals for the 1993 peak discharges and the effective record lengths for 1993 . Of the 28 gaging stations that had small flood magnitudes in 1993 and long record lengths, the difference between the 1992 and the 1993 flood-frequency analyses for 100- year recurrence-interval discharges at 22 gaging stations was less than 5 percent. Of the 10 gaging stations that had large flood magnitudes in 1993 and short record lengths, the increase in 100-year recurrence-interval discharges at 9 gaging stations was greater than 15 percent.
Mississippi River basin↗
Relations between pesticide use and riverine flux in the Mississippi River Basin
In an intensive subcontimental study of pesticides in surface waters of the United States, concentrations of 26 high-use pesticides were measured at nine sites in the Mississippi River basin from May 1991 through March 1992. Calculated total fluxes were combined with agricultural-use data to estimate the percentage of applied pesticide reaching the mouths of the Mississippi River and six major tributaries. For most pesticides, the riverine flux was less than 2% of the mass applied agriculturally. The insecticide diazinon was detected frequently in rivers draining the three basins with the highest population densities, apparently as a result of urban use.
Mississippi River basin↗