This picture shows an aerial view of a sewage outfall plume in coastal waters.  The plume source is near the darkest concentration reagion.  The plume is intruding (pancaking) into a narrow layer.  At the time the picture was taken, the mean current field was moving the plume off-shore.

This picture shows a tracer-study plume conducted at the mouth of a river entering into an estuary.  One can clearly see the fine-scale structure of the plume interacting with ambient turbulence and the slow nature of lateral spreading.  

Here, a tracer study is conducted in a river.  Although vertical mixing of the tracer is achieved very quickly (rule of thumb is 10 river depths downstream), complete lateral mixing takes much longer.  

This is a picture of the same dye study show above, but viewed from further downstream.  It is clear in the picture that the curve in the river strongly enhances the lateral mixing of the plume. 

This is an old photograph showing the waste outfall from a chemical plant on the Alpenrhein in  Germany.  The photograph clearly shows the slow lateral growth of the plume.  Such strong plumes that are clearly visible are no longer allowed due to today's stricter discharge regulations.

This is another old photograph in the same region showing two separate discharges.  In the lower left (near the bridge) is a light-colored discharge; in the middle top is a darker colored discharge.  Do to lateral recirculating currents in the river, the light discharge spreads rapidly to the right making the darker colored discharge visible.  Again, such potent discharges are rare today due to the stricter regulation of point discharges.

Here we see the junction of two rivers, the Hochrhein and the Aare in Germany.  The mixing of the water from the two rivers is made visible by the higher sediment concentration in the river on the right.  

This spectacular picture shows the joining of three different rivers.  The Danube, with very high particulate concentration, on the left joins with the two rivers on the right.  The larger of the two rivers carries a higher particulate load, thus the darkest (cleanest) smallest river is also visible.  Notice how sharp the boundaries are separating the various river flows.  

Photo of open water lead downstream of a diffuser. Photo by
Mark Spafford from Alberta-Pacific Forest Industries Inc (AlPac).