Hydrologic and climate trends for the Coldwater River watershed in south-central British Columbia, Canada

Abstract

Historical trends in streamflow and climate were investigated for the Coldwater River watershed in south-central British Columbia, Canada. Temporal increases in rainfall and total precipitation during the spring, summer, and autumn periods, as well as on an annual basis, at the city of Merritt near the mouth of the watershed, and year-round temperature increases at this site, compare with declining summertime and annual streamflows at the nearby Merritt hydrometric station on the Coldwater River. Declining summer flows at this site could reflect the dominance of temporally increasing evaporation that is offsetting increased precipitation over the same periods of the hydrologic year. Alternatively, increased water abstractions, altered regulation regimes, and/or land use changes in the watershed may also play significant/dominant roles. The relative absence of any coherent hydrological temporal patterns at the upstream Brookmere hydrometric station on the Coldwater River suggests that the net effects of warming temperatures, increasing precipitation, and any anthropogenic drivers over the past four decades are in approximate balance.