Warmer weather in most of the Northern Hemisphere means a lot more water will start to flow from one place to another… and as it does it could pick up all sorts of unpleasant, and potentially harmful, drinking water contaminants.
As an example, the rise and fall of aquifer levels in certain parts of the United States can have a pronounced effect on dissolved arsenic levels in the water contained in those aquifers.
As a second example, water from melting snows or from Spring showers traveling across the land in agricultural regions has a tendency to pick up potentially harmful bacteria and nitrates/nitrites that could work their way into poorly capped wells.
Other unwanted drinking water contaminants such as atrazine and simazine also get picked up runoff water making its way through the countryside. As you may recall, farmers in the United States used both of those compounds, especially atrazine, as an herbicide/pesticide for many years — and therefore it ought not surprise you that pockets of washed away atrazine lurk in many unsuspecting parts of the country.
