Changes in Microbial Quality of Irrigation Water under Different Weather Conditions in Southeast Norway

Abstract

A short-term study concerning the impact of weather fluctuations in Southeast Norway on microbiological quality of irrigation water sources was performed. The weather variations were related to a relatively dry and warm period followed by rainfall events associated with lower air temperatures. Samples of water from a ground well, a pond and a stream, all used for sprinkler irrigation of fruit and vegetable crops, were investigated for contamination with faecal indicator bacteria (Escherichia coli - E. coli) and intestinal parasitic protozoa (Cryptosporidium oocysts and Giardia cysts). Although the groundwater was not contaminated with these microbes during either period, contamination was detected in surface waters, with concentrations up to three times higher during the wet/cool period than during the dry/warm period. An increase in microbial concentrations was observed immediately after the first rainfall events. These results demonstrate that surface waters commonly used for irrigation in Southeast Norway are vulnerable to contamination with microbes and this is related to weather fluctuations. These outcomes are of relevance when considering the impact of predicted climate change and contamination of agricultural water supplies.