As briey mentioned, sampling, monitoring, and analyses are the key elements of a measurement program. Treatment, assessment, and use of data related to the quality of urban wet weather pollution require that these elements be well performed. The “nature” and the “empirical basis” focusing on the way of achieving information in terms of data, often quite different compared with similar considerations in case of dry weather, will be emphasized. It is not an objective to deal with details like specic methods for monitoring and analysis, types of equipment, or different statistical methods. Such specic details can be found elsewhere in texts and technical publications (Wiersma 2004). In case of chemical analyses, APHA-AWWA-WEF (2005) is a central source for information. A number of specic methods and technologies in terms of stormwater sampling, monitoring, and analysis are found in Burton and Pitt (2002) and principles for data acquisition within urban water management are focused on in Fletcher and Deletic (2007). Numerous textbooks on statistical methods exist, for example, Miller and Freund (1965) and several procedures are available via the internet.