Snowmelt and Toxicology
With pictures of roofs cracking under masses of snow on TV in Europe and Northern America it is time to focus on the impact of snowmelt on aquatic ecosystems. Snowmelt when augmented with rain is not only a heavy load on roofs but also a load for influenced rivers and lakes which are to receive the contained pollutants. After several months of frost airborne deposits that have been conserved in the snow masses, and soil matter that has been disrupted by ice are now leached into the run-off, sometimes within a few days. This allows certain toxic solutes to enter the aquatic environment.
 Foto by J Reynolds, with permission | It has been shown as early as 1978 that arsenic gets mobilized from soil and the arsenic burden rises in Texas (-> Richardson &&, J Environ Qual, 7(2): 189-192) and elsewhere each year, due to the geologic occurrence of the element. Apart from heavy metals (e.g. aluminum, cadmium, chromium, copper, kead, zinc) other toxic pollutants like oil and grease, hydrocarbons, can be detected. Compared to ordinary rain snowmelt is more acidic. It will mobilize many pollutants that would stick to soil under more alkaline conditions, e.g. aluminum and other (toxic) metals. In addition it contains all the dust and fallout that has been accumulated in the snow since last rainfall (sometimes from several months) and keeps it frozen until melting mobilizes and concentrates the matter from the large snow masses down to a thin surface film. |
When the melted snow starts running off to nearby creeks and lakes it will likely mess up the affected ecosystems. As a result fish die-off and other more subtle changes will occur and propagate until becoming more and more diluted. Sometimes several adverse accidents combine as happened to the Hungarian river Tisza in March 2000, when snwomelt and heavy rain caused a dam break of an upstream mine tail settling pond and release highly toxic cyanide and heavy metal salts into the environment.
There are several areas where such pollutants have to be strictly avoided. Such sensitive areas include:
- Coastal Counties ‡ to protect sensitive coastal waters
- Water Supply Watersheds ‡ to protect waters that are used as drinking water supply sources
- High Quality Waters and Outstanding Resource Waters ‡ to protect waters that have unique water quality or unique resources.
- Nutrient Sensitive Waters ‡ to reduce the inputs of nutrients from urban and developing areas.
There is also a US federal program (the National Pollutant Discharge Elimination System (NPDES) Stormwater Program) that requires stormwater permits for point source discharges of stormwater from certain industrial activities and from large municipalities (population 100,000 or larger). Other countries have issued their own regulations how to deal with snowmelt (and storm waters), but the issue recurs every year, inflicting severe damage on ecosystems and dependent economies.
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What can be done? A recommended remedy whereby the impacts of snowmelt runoff on aquatic systems can be minimized is by storing snow in upland areas to promote infiltration, more nearly approaching pre-development hydrology. It also provides an alternative to disposing of snow directly into streams, reducing the capacity for "shock" loadings.
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2:44:01 AM 
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