Human impact on rivers
Man impacts rivers in many ways. The often harmful flow of substances produced by humans is referred to as emission or load. Solid matter, humus, certain metals, nutrients and acidifying substances leach into rivers as a consequence of land use and point loading within a drainage basin. These substances cause many kinds of changes in the aquatic environment and also in the species distribution and abundance of aquatic organisms. Moreover, often the recreational value of the river becomes diminished. Often human actions also change the river flow or the shape of the riverbed. This happens, for example, when riverbeds are cleaned or the water flow is regulated.
What is total loading composed of?
The term ‘total loading’ refers to all the loading that impacts on a water system, i.e. natural leaching, deposition, non-point loading and point loading.
Natural leaching describes substance flow that enters a water system from a drainage basin naturally without any human involvement. River organisms are dependent on natural leaching. They utilise efficiently and in many different ways the organic substances and nutrients that leach into a river naturally.
Deposition is matter that transfers from air to water or to earth either with rain (wet deposition) or as dry deposition. A major part of harmful deposition derives from industrial and traffic emissions; such deposition consists of sulphur compounds and nitrogen compounds. Sulphurous compounds cause acid depositions (a.k.a. acid rain). Natural depositions are produced, for example, when volcanoes erupt.
Non-point loading originates from several small sources of emission, such as agriculture, forestry, scattered settlements and holiday settlements. Often, experiments, calculations and models must be used in order to assess the amount of non-point loading.
Point loading refers to environmental loading, the source of which can be determined precisely. Examples of this include industry in general, fish farming, peat production and fur farming.
The foremost causes of loading are A) drainage waters from agriculture, forestry and peat production, B) wastewaters from communities, the industry, animal farming, fish farming, scattered settlements and holiday settlements, and C) drainage waters and leaching from urban population centres, mines and waste treatment areas. Deteriorated sediments in water systems that have been exposed to loading can also cause significant loading to water systems. Moreover, airborne deposition can impair the state of water systems, e.g. by causing acidification.
Those responsible for operations that cause significant point loading are obligated by Finland’s environmental legislation to participate in the monitoring of this loading. This involves monitoring of the substance amounts that enter a water system. Often it also entails monitoring of the impacts a substance has on a water system.