A phosphorus budget for river basins of the United States

Abstract

Phosphorus budgets were calculated for 261 river basins ranging in size from twenty to 30,000 square miles which together comprise the major drainage areas of the U.S. County based estimates of phosphorus loadings to these drainage areas were compared to estimates of phosphorus transport within major rivers of the U.S. Mean estimates of phosphorus transport as measured at national stream quality monitoring stations were calculated by two methods: averaging the historical monthly record and averaging the daily record obtained by integrating the discharge and phosphorus transport relationship over the daily flow record. The Colorado, Rio Grande and Upper Missouri drainage areas containing large main stem reservoirs retained the largest quantities of phosphorus. In general, phosphorus transport was more conservative with decreasing drainage area. However, little accumulation of phosphorus was observed along the main stems of the Ohio and Mississippi Rivers where large flows with little variability appeared to enhance the transport of phosphorus.