The multiple jets in crossflow is a fluid flow problem related to many environmental and industrial applications including wastewater discharge into the coastal water, injection of oxygen to raise the DO level of the lypolimnion in stratified lakes, gas injection in combustion chambers, to deplete marine phytoplankton through siphonal currents, etc. This book is mainly concerned with the behavior of individual jet trajectories in a group abstracted from LIF images that interpreted with Lagrangian model. The ADV measurement gave 3D understanding of the flow structure. A first order conceptual model is developed to interpret what was observed in the experiment. Some truly new results have come out of this work, and the near field interference of multiple jets has now been clarified and is now predictable by mathematical models. The fundamental concept of single jet flow is also demonstrated in this book. It may be used as a reference by postgraduate students and researchers in environ. fluid mechanics, physics, mechanical and chemical eng., earth and environ. sciences.