A NEW TOTAL MAXIMUM DAILY LOAD (TMDL) MODEL FOR THE DELAWARE RIVER

摘要

In 1990, the Delaware River Basin Commission issued the results of the DelawareEstuary Use Attainability Project, which recommended higher dissolved oxygenstandards for the Delaware River in order to meet the 'fishable' goals outlined in theClean Water Act. The implementation of the proposed standards required twoquestions to be answered: 1) Is a new BOD allocation for the Delaware Rivernecessary?, and 2) If a new BOD allocation is necessary is a new TMDL modelingframework needed? Based on a review of the historical water quality data, the currentand potential BOD loadings to the river, and the use of mathematical models indescribing the river over the past thirty years, the answer to both questions is yes.Although the current dissolved oxygen levels indicate that the river is meeting, or isvery close to meeting, the proposed standards, the current BOD load discharged tothe river is well below the allocated amount, and continued water quality success isnot guaranteed. As water quality has improved since the 1960s, the magnitude andrelative importance of the different biological, chemical and physical processesaffecting the dissolved oxygen balance in the river have changed. A new TMDLmodeling framework was, therefore, needed to accurately represent the currentcondition of the Delaware River.