|Water chemistry is responsible for many of the characteristics associated with the "quality" of a
river (see the general section on water chemistry). It is a reflection of complex interdependent
relationships involving the river, the atmosphere, the surrounding soil and rocks, groundwater,
sediments and living systems. |
Rivers have been called the "gutters down which flow the ruins of continents". The world's rivers dump 2.25 x 1010 metric tons of dissolved and particulate matter from erosion of the land into the seas every year, thus playing a major role in global biogeochemical cycling. The river, however, is more than just a transporter of materials. It is also a processor of materials as the biota it contains take up, convert, use and release materials that come to them. It is useful to think of a river as an active biological system that metabolizes the organic matter contained within it. The water that arrives at the mouth of a river is far different, both quantitatively and qualitatively, from what was present in the waters nearer the source.