Integrated water-quality management indicators from river to sea: A case study of the Bohai Sea, China.

Considering the interrelatedness of river and bay ecosystems, river and bay water quality management is shifting to integrated management across coastlines. Here, an integrated management indicator for the coordinated and efficient nitrogen abatement of the Bohai Sea and its basin was proposed. The terrigenous total nitrogen (TN) allocated load was optimized under the dual water quality constraints for both river and bay using a simulation–optimization method. The contributing jurisdictions were identified by their TN overload rates, and their responsibility apportionment rate for specific nitrogen-polluted segment was quantified. Integrated TN reduction scheme resulted in a 29 % greater reduction in bay and river nitrogen pollution than the equal proportion reduction approach. In 18 % of the watersheds in the Bohai basin, the water quality standards of the river were more restrictive than the standards of the bay. Integrated management scheme has higher coordination of river and sea management objectives. [Display omitted] • Allocated load is for water quality objectives of both Bohai Sea and its basin. • Contributing jurisdictions for each nitrogen-polluted segment was indentified. • Integrated nitrogen management scheme for bay and its basin is high-efficient. • Simulation-optimization method is suitable for multi-objective management. [ABSTRACT FROM AUTHOR]