Which water system would you expect to have the lowest dissolved nutrient content?

The answer is rain-fed stream. It is that part of rainfall which arrives the stream directly after the rainfall happens. When all losses are content and if rain is still sustained with the rate larger than in filtration rate at this period the excess water creates a head over the ground surface which is the surface detention that tends to move from one place to another recognized as overland flow. As soon as the overland flow links to the streams, channels or oceans called as surface runoff.