Northern Prairie Wildlife Research Center
U.S. Geological Survey, Water Resources Division, 821 East Interstate Avenue, Bismarck, ND 58501
2,4-D is a synthetically produced organic compound used as a herbicide for wheat and other small grains. It is the most commonly used herbicide in North Dakota. The fate of 2,4-D in agricultural soils is well defined; however, little is known about the transport and fate of 2,4-D in prairie streams. In 1992, the U.S. Geological Survey, in cooperation with the Three Affiliated Tribes, began a nonpoint-source investigation of agricultural chemicals in prairie stream tributaries to Lake Sakakawea on the Fort Berthold Indian Reservation. During the first year of the study, 2,4-D was detected in streams on the east side of Lake Sakakawea, where agricultural activity is greatest. These streams are ephemeral, have relatively large drainage areas for the amount of discharge, are recharged by saline ground-water, and have large dissolved-solids loads.
Discharges of six to eight prairie streams will be measured and the streams will be sampled for major-ion, nutrient, and 2,4-D concentrations four times during May-August 1993. At least two streams will have more than one sampling location to facilitate the identification of transport processes. In addition, land-use data are being compiled in a geographic information system data base. The resulting information will be used to: (1) document spatial and temporal variability in 2,4-D concentrations in prairie streams on the reservation; (2) evaluate variations in 2,4-D concentrations in prairie streams on the reservation as a function of land-use; and (3) determine the transport of 2,4-D in prairie streams on the reservation using discharge data and 2,4-D concentrations.