WHAT ACTIONS, ACTIVITIES OR PRACTICES TEND TO REDUCE NATURAL WATER PURIFICATION?

The process of natural water purification is one that involves many steps and unfortunately, is one that is easily disrupted by the actions of man. How is this so you may ask? It starts by understanding some important facts about water.

Water is a solvent and a medium for transfers of mass and heat. Perhaps most important, water is necessary to sustain life. As water travels along a hydrologic pathway, such as groundwater moving from a recharge area to a spring, a variety of interactions occur that are associated with the type of geologic media and with the biota. The interaction causes some chemical elements to dissolve and precipitate, while others transform, such as the oxidation of iron and the change of one nutrient species to another.

Particles not only interact with the water, but can be transported by the water depending on the mass, size, and shape of the particle, the water velocity, and the material through or over which the water flows. Living organisms, particularly microorganisms such as phytoplankton and bacteria, affect water quality genesis through several mechanisms. For example, the biota can use and release nutrients and other elements that are commonly specific to particular plants and geographic regions or generate other products, including gases.

Natural water quality varies markedly and is affected by the geology, biology, and hydroclimatic characteristics of an area. Even under natural conditions, water may be toxic or otherwise unfit for human consumption. The occurrence of high and toxic metal concentrations is not uncommon and can be attributed to weathering of naturally occurring ore deposits. Although generally non-toxic, the solute concentrations of “pure” bottled spring water can vary by several orders of magnitude worldwide. However, the concept of pollution is relative, in that it reflects a change from some reference value to a value that causes problems for human use.

Human influences have had a direct effect on the hydrologic cycle by altering the land in ways that change its physical, chemical, and biological characteristics. Physical alterations such as urbanization, transportation, farming (irrigation), deforestation and forestation, land drainage, channelization and damming, and mining alter hydrologic pathways and may change the water quality characteristics by modifying the materials with which the water interacts. For example, the impervious surfaces created by urbanization produces overland flow and high amounts of runoff even at moderate rainfall intensities. In addition, these human activities alter water quality not only by changing hydrologic pathways, but by the addition of substances and wastes to the landscape. These activities include application of pesticides, herbicides, and fertilizer, and leaching to groundwater and surface water from landfills, mine tailings, and irrigated farmland.

Most natural water purification occurs as water moves through and is filtered by soils, wetlands and riparian areas. Therefore, anything that degrades the quality or size of these natural filters, anything that causes water to bypass these filters, or anything that overwhelms these filters with excess water volume or excess pollutants will reduce their effectiveness for purifying water.

The primary things that obstruct natural water purification include the following:

1. impervious areas,
2. altered waterways or other hydrologic modifications,
3. loss in acreage of wetlands or riparian areas,
4. invasive plant and animal species, and
5. excessive pollution, especially from nitrogen.

Impervious surfaces such as paved parking lots, roads and highways will accelerate runoff, increase flooding, and often funnel contaminated water directly into lakes, streams, rivers and coastal waters, completely bypassing natural filters.

Urban sprawl is a growing threat to natural wetlands and forest ecosystems. Diversion and altering flow in natural aquatic systems and waterways can reduce their capacity for effective purification. Dredging of waterways to maintain navigation channels has destroyed many acres of natural wetlands and contaminated many others. Removal and replacement of riparian forest areas with non-vegetated land uses or impervious surfaces reduces streams' and rivers' capacity to cleanse themselves. The introduction of exotic species of plants and animals can eliminate native species and alter an aquatic system's productive capabilities and its ability to cycle nutrients. States are now spending many millions of dollars to combat invasive plants and animals, both land and aquatic species.

It's easy to see that human activities in the landscape result in alterations of hydrologic pathways by physically altering the land, by changing the vegetation, and by artificially routing water to where humans want it. In addition, human activities have affected water quality by adding substances (gas, liquid, and solid). Human requirements for sustainability, cultural characteristics of the population, socioeconomic situations, and the biophysical and climatic settings of an area determine the level of interaction, and consequently, the rate of land and water degradation.