Basin-wide considerations for water quality management: Importance of phosphorus retention by reservoirs

The relationship between phosphorus retention (R-P) and water residence tim e (R-T) was assessed for selected U.S. Army Corps of Engineers reservoirs a nd found to be influenced by areal phosphorus loading rate (P-L). For reser voirs with high P-L (>15 gm/m(2)/yr), R-P increased markedly with modest in creases in R-T. Reservoirs with lower values of P-L exhibited less dramatic responses in R-P to changes in R-T. The water quality management implicati ons of this are great since reservoirs for which marked changes in R-P can occur with modest changes in R-T are potential management loci within a dra inage basin.