Effect of human land development on water quality
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Abstract
Conversion of natural landscapes to agriculture or urban areas results in a cascading series of events that degrade the quality of nearby (receiving) water bodies. Removal of the forest cover reduces evapotranspiration of rainfall and increases surface stormwater runoff, causing erosion and suspended sediment pollution of receiving waters. If the land is converted into agriculture a number of pollutants may subsequently enter surface and/or groundwaters including suspended sediments, nutrients (nitrogen and phosphorus), pathogenic fecal microbes, and pesticides and herbicides. If the cleared land is urbanized much land will be covered by impervious surfaces which will cause further increases in runoff and the loss of groundwater recharge, erosion of streambeds, and loss of aquatic animal habitat. If the area is to be served by septic systems nutrient and fecal microbial pollution to nearby wells and waterways may result if the soils are porous and there is a high water table; surface runoff may result if soils are too impervious for proper percolation. Urban stormwater runoff will lead to pollution of receiving surface waters by nutrients, fecal microbes, metals, and toxic chemicals including PCBs and PAHs. The amount of impervious surface coverage in a watershed is strongly related to degraded fish and invertebrate communities, increases in nutrient and chemical pollution and increases in fecal microbial pollution. Agricultural and urban runoff can be treated by constructed wetlands, streamside vegetated buffer zones, and the use of proper irrigation techniques. Urban runoff can also be treated by properly designed wet detention ponds, and the use of sand filters and rain gardens. Urban runoff can be minimized by reducing runoff at the source through increasing greenspace and minimizing impervious surface coverage. A variety of non-technical means to protect water quality may be available including the use of conservation easements and financial incentives to landowners.
