Understanding and predicting the impact of various
sources are essential components of a typical course on Analysis of Stream
and Estuary Pollution in an engineering curriculum. Dispersal and decay
of contaminants in lakes, streams, estuaries, and oceans. Effects of pollutants
on chemical quality and ecology of receiving waters.
Completely Mixed Systems
It is often useful to describe lakes and reservoirs
under the assumption that the body of water is completely mixed horizontally
and vertically. The substance decays is assumed with a first-order decay
coefficient and with constant parameters of flow Q, decay K, over time.
A mass balance for the lake is then given by
Case I : No Input Concentration
If W is zero, that is, there are no inputs of
the concentration, and the solution is
Figure 1 shows the "flushing" of a lake initial condition.