Analysis of Methodologies for Assessment of Urban Drainage Impacts in Lakes and Reservoirs

The water quality of rivers, lakes or reservoirs changes in both short and long term. For a given catchment with known pollution sources, different combinations of hydrologic and pollutants discharges scenarios may result in different impacts in the water quality. The objectives of the present work were to analyze the methodologies currently used for assessment of pollution impacts in lakes and reservoirs, and to get an insight on how much research focus on urban drainage as a pollution source. Based on the evaluation of a sample of 17 papers, dated between 2000 and 2012, from different countries it was concluded that monitoring data is the most used method for studies in water quality of lakes and reservoirs. Records from historical databases or from continuous monitoring are used by some authors; but most of the time the research includes a designed monitoring program. It was interesting to realize that the application of three different methodologies i) simple modeling; ii) simple monitoring and iii) analysis of long term monitoring data to assess the impacts of road runoff and agriculture discharges in a reservoir in Central Portugal resulted in similar conclusions, emphasizing the importance of long duration monitoring records. Most of the analyzed papers evaluated agriculture pollutants. Nevertheless, it has been proved that road runoff may discharge pollutants in concentrations that exceed the limits for point wastewater discharges; therefore it seems there are improvements that should be made in future studies of pollutant impacts in lakes and reservoirs.