Why is the water dark when it rains?

This, more brownish color, that we can observe in the waters, happens due to the increase of the terrestrial runoff. An enormous amount of rainwater coming from the earth, which brings several nutrients (such as silicates, phosphates and nitrates) and sedimentary particulate matter (sands, fine earth).

Thus, on rainy days, we can see a different watercolor compared to ones on regular days.