Influence of climate variables on the concentration of Escherichia coli in the Rhine, Meuse, and Drentse Aa during 1985–2010

This study evaluates the relationship between the climate variables temperature and precipitation and the concentration of Escherichia coli bacteria in the Rhine, Meuse, and Drentse Aa for the period 1985–2010. Data from 4,679 E. coli concentration measurements spread over a total of 13 locations in these three river systems were used in this study. The variables water temperature, precipitation, and river discharge were correlated with E. coli measurements. Water temperature was found to correlate negatively, and this is in line with expectations that higher temperature increases microorganism die-off. Precipitation and discharge were found to correlate positively, and this is in line with expectations that runoff from agricultural lands brings along pathogens from manure and increases the chance of sewer overflows. The data of the Meuse were fit to a linear model that explained E. coli concentrations from a time component, the climate variables and a locations dummy variable, in order to assess the relative contribution of the different variables. This model had an R2 of 0.49, meaning that climate variables and location can account for nearly half of the observed variation in E. coli concentrations in surface water, even when other factors, such as land-use variables, are not taken into account. The effect of the different climate variables was found to differ with scale, with temperature being relatively important at a local scale, and discharge being mainly of importance at larger scales. From our results, we expect that climate change, mainly the projected increased precipitation, may increase E. coli concentrations overall. Other waterborne pathogens that follow similar transmission pathways as E. coli may be similarly impacted by climate change