Load-detention efficiencies in a dry-pond basin

Inflow and outflow to a dry-pond detention basin in Topeka, Kansas, were monitored for 19 storms during a 14-month period. Samples of runoff were collected automatically at two inflow and one outflow locations. Inflow and outflow constituent loads were computed with subsequent computation of load-detention efficiencies. Three constituents (dissolved solids, ammonia plus organic nitrogen, and total organic carbon) had negative (larger loads out than in) median detention efficiencies (-78.5 percent, -9.0 percent, and -3.0 percent, respectively). Median detention efficiencies for the other constituents were: suspended solids (2.5 percent), chemical oxygen demand (15.5 percent), nitrite plus nitrate nitrogen (20.0 percent), ammonia nitrogen (69.0 percent), total phosphorus (18.5 percent), dissolved phosphorus (0.0 percent), total lead (66.0 percent), and total zinc (65.0 percent).