RAINFALL INDUCED CHANGES IN CHEMISTRY OF A BRITISH-COLUMBIA COASTAL STREAM

A small coastal stream in British Columbia was sampled during two storm events to measure stream chemistry changes. Samples were collected at 30 minute intervals throughout the storms to assess changes in stream chemistry on a temporal basis. During rain events, streamwater showed a decrease in chloride, nitrate, and sulphate concentrations. Stream pH decreased by 0.3 units during these events while the buffering capacity, measured as alkalinity, appeared to be consumed in addition to dilution effects. After the storms, stream chemistry tended to slowly return to the pre-storm conditions over a period of several days. Results showed that rainstorms drive marked chemical changes on a scale of hours.