A lake receives 3000 metric tons of phosphorus
per year, half from point sources and half from nonpoint sources.
The phosphorus has led to a lot of algae growth and the Secchi
disk transparency is less than 1m. Our goal is to increase the
Secchi disk reading to 3m, a good depth for recreational use.
To manage the lake, reduce the point and nonpoint phosphorus loads
until the transparency goal is met. There are several combinations
which will do this, but there is a ‘best’ answer – the
combination that meets the goal at the lowest cost.