Within the European Union, and maybe especially in Scandinavia, access to clean water is taken for granted without a second thought. However, it is not often realized that many of the human activities put a great burden on water quality and quantity. All polluted water, whether polluted by households, industry, agriculture, or traffic returns back, in some way, to the environment and may cause damage to human health or the environment. The increasing demand for cleaner rivers and lakes, groundwater and coastal beaches was the driving force for the EU Water Framework Directive which overall aim is to obtain, and keep a "good status" for water within EU. The protection should include all waters, surface waters and groundwater and should be achieved before year 2015. With these increasing demands upon water quality, further research is required in terms of the quantity and quality of road runoff.Further research is required particularly in areas with a cold climate since special conditions occur - storage of precipitation and pollutants in snowpacks during extended time periods, processes in the snowpack influencing the availability of pollutants, and dissimilar surface and transport network due to snow and ice. As a result, the runoff quantity and quality will differ compared to snow and-ice free climates (Marsalek, 2003). Also, it is of importance to realise that areas with cold climate can be subdivided into smaller areas with different climatic zones. For example, when looked upon Sweden, the winter could be divided into two different types. One type of winter climate, which is found in the south of Sweden, has a temperature often fluctuating around zero. Snowfall is received occasionally when the temperature is below zero, however, the snow is melting instantaneously or shortly after the snowfall. The other type of winter climate is what could be found in the north of Sweden, having long periods with temperatures below zero degrees. During this time there is an accumulation of snow and pollutants until the spring time when the temperature is fluctuating around zero and the snowmelt begins. This melt period resemble the winter climate found in the south of Sweden and is critical when it comes to risks connected to both quality and quantity. The highest concentrations of pollutants and the highest flows are found during snowmelt and rain-on-snow events respectively. There are many differences between the two different winter climates. The usage of salt on roads as a slipperiness control measure is more common in the southern parts of Sweden. Since the temperature often is around zero during winter time, the build-up of ice layers on roads are common. In the north of Sweden, it is often too cold to have a build-up of ice and the de-icers do not work at these low temperatures. Another difference is that the build up of pollutants is more significant for the winter climates with long, cold periods since the freezing-thawing cycles are not as frequent. When this accumulated snow is starting to melt, we get large quantities of water and also high concentrations of pollutants. However, to decrease the impacts from road runoff in cold regions, it is critical to not only understand the dynamics of pollutants, but also to use this knowledge in models to predict and prevent environmental damage. In this article the winter season will be subdivided into three different climategroups, one group where the temperature stays below zero during the whole winter period, the second group where the temperature is fluctuating between plus and minus five degrees, and the third group where the temperature is above zero degrees during the whole winter period. Processes and influencing factors will be investigated for all three groups in terms of dynamics of snowmelt and runoff and the quality of stormwater during the different conditions, see Figure 1. Also, a selection of commonly used models of today will be investigated and compared to see what equations are describing these physical and chemical processes. Figure1. Factors affecting the stormwater quantity and quality. Marsalek, J. (2003). Road salts in urban stormwater: an emerging issue in stormwater management in cold climate. Water, Science and Technology, vol. 48, No.9, pp 61-70.
2006.
International Conference on Urban Drainage Modelling : 02/04/2006 - 07/04/2006