Hydrologic characteristics of Bear Creek near Silver Hill and Buffalo River near St. Joe, Arkansas, 1999-2000

The Buffalo River and its tributary Bear Creek are in the White River Basin in the Ozark Plateaus in north-central Arkansas. Analysis of streamflow measurements and water-quality samples at a site on Bear Creek and a site on the Buffalo River in Searcy County, Arkansas, quantify differences between the two sites during calendar years 1999 and 2000. Streamflow and water quality also vary seasonally at each site. Mean annual streamflow was substantially larger at the Buffalo River site (836 and 719 cubic feet per second in 1999 and 2000) than at the Bear Creek site (56 and 63 cubic feet per second). However, during times of low flow, discharge of Bear Creek comprises a larger proportion of the flow of the Buffalo River. Concentrations of nutrients, fecal-indicator bacteria, dissolved organic carbon, and suspended sediment generally were greater in samples from Bear Creek than in samples from the Buffalo River. Statistically significant differences were detected in concentrations of nitrite plus nitrate, total nitrogen, dissolved phosphorus, orthophosphorus, total phosphorus, fecal coliform bacteria, and suspended sediment. Loads varied between sites, hydrologic conditions, seasons, and years. Loads were substantially higher for the Buffalo River than for Bear Creek (as would be expected because of the Buffalo’s higher streamflow). Loads contributed by surface runoff usually comprised more than 85 percent of the annual load. Constituent yields (loads divided by drainage area) were much more similar between sites than were loads. Flow-weighted concentrations and dissolved constituent yields generally were greater for Bear Creek than yields for the Buffalo River and flowweighted concentrations yields were higher than typical flow-weighted concentrations and yields in undeveloped basins, but lower than flow-weighted concentrations and yields at a site in a more developed basin. INTRODUCTION The Buffalo River and its tributary, Bear Creek, are in the White River Basin in the Ozark Plateaus physiographic province (Fenneman, 1946) in northcentral Arkansas (fig. 1). Most of the Buffalo River and a part of Bear Creek near its confluence with the Buffalo River lie within the boundaries of the Buffalo National River. A better understanding of the hydrology of this area is of interest to many, including the National Park Service, which administers the Buffalo National River. To contribute to this understanding, the U.S. Geological Survey (USGS) conducted a study to describe and compare streamflow and water-quality characteristics for a site on Bear Creek and a nearby site on the Buffalo River. This study is part of the National Park Service (NPS)/USGS Water-Quality Monitoring and Assessment Partnership. Studies conducted as part of the Water-Quality Monitoring and Assessment Partnership are designed to contribute information that would enhance the understanding of NPS water-quality management issues. Because Bear Creek is one of the larger tributaries of the Buffalo River it can have a substantial effect on water quality and streamflow of the Buffalo River, and therefore on water-quality management issues. Immediately downstream from the confluence of Bear Creek and the Buffalo River, 9.8 percent of the Buffalo River’s drainage area is contributed by the Bear Creek Basin. Relative to many other tributaries of the Buffalo River a large part (28 percent) of the Bear Creek Basin is cleared land (Panfil and Jacobson, 2001). Previous investigations (Mott, 1997; Steele and Mott, 1998) have indicated that Bear Creek (and other nearby tributaries with relatively large percentages of clear land within their basins) may contribute to elevated concentrations of nitrate in the middle section of the Buffalo River (a water-quality management issue). The recent decision (August 2001) of the U.S. Army Corps of Engineers to issue a federal permit, in response to an