Characterization of natural and environmental flows in New Brunswick, Canada

A good understanding of the natural flow regime plays an important role in many hydrological studies. Also important in such studies is the quantification of environmental flows. This study focuses on flow metrics that best describe the natural flow regime and the hydrological characteristics for rivers in New Brunswick (Canada) as well as quantifying environment flows for these rivers. New Brunswick rivers have a mean annual flow (MAF) of approximately 23 L s(-1) km(-2), which is also reflective of the water availability. The frequency analysis showed that low flows (T = 2-50 years, where T is the recurrence interval) were all below the 10% MAF. Environmental flow methods based on the MAF and flow duration analysis (median flow) showed good regional regression equations. However, flow duration methods showed high variability especially at flows between Q(80) and Q(100). Flow targets based on the 25% MAF, Q(50) and 70% Q(50) were used to estimate environmental flows, particularly during low-flow periods (winter and summer). Results showed that the 70% Q(50) method should be used with caution in summer as this method provided flows in the range of 15-16% of MAF. Other methods provided environmental flows higher than 15% MAF, thus, providing better flow protection for aquatic habitat. When comparing water availability for off-stream use (river flow-environmental flow), different parts of New Brunswick were found to be deficient in flows (i.e., river flows less than environment flows-no extractable water) during the summer and winter low-flow periods.