In this study attempts are done to apply the Mike 11 numerical water quality model for the evaluation of existing water quality conditions and a prediction of effects of different wastewater and other pollution control schemes under the Yamuna Action Plan. The Mawi-Delhi (Okhla Barrage) stretch has been taken for this study. From the application of model it was found out that water quality between Mawi-Wazirabad reach is significantly affected by the large growth of phytoplanktons causes 80 % to 135 % DO saturation, while in Delhi the quality is so bad that photosynthesis processes are absent. BOD removal mainly takes place by settling of organic matter. The calibrated model is subsequently applied for predicting the water quality for the waste load reduction schemes of the Yamuna Action Plan. It was found out that the water quality of the river in upstream of Delhi would be increased form class B (BOD<3mg/L) to class A (BOD<2mg/L), while for Delhi segment water quality improved considerably but still would be poor, not even to the class D. By the application of certain suggested DO control technologies along with the Action Plan, the water quality will improve to class D (BOD<6 mg/L), so that it can be use for wildlife and fisheries. Additional flow of 40 m(3)/s (total flow 60 m3/s) can also increase the water quality to the class D. (C) 1997 IAWQ. Published by Elsevier Science Ltd.
