Variations of climate and streamflow over the Saint John Basin since 1872

Long-term climate and streamflow records for the Saint John River Basin of Quebec, Maine and New Brunswick were examined in order to determine what may happen in the Basin's future and to understand to what extent the Basin's experience reflects broader-scale changes over North America and the rest of the world. The physical characteristics of the Basin were described, including a list of the main dams and hydraulic stations above the Mactaquac. The Saint John River appears to have changed its habits in the past four decades. The spring freshet has tended to come earlier and has increased in volume since 1972. There is no evidence, however, that this change has been caused by the greenhouse effect. No enduring changes in mean annual precipitation and streamflow were detected. The mean annual temperature has risen 1.3 degrees C since 1871, or about 1 degrees C per century. Snowy or wet winters with high interannual variability have resulted in earlier thaws and several major flood and ice-jam events. The risk of severe rainstorms at the time of freshet can lead to higher flows than have been recorded in the past. 19 refs., 3 tabs., 10 figs