The demand for water withdrawal from rivers continues to increase world‐wide, and these water withdrawals can affect fish habitat and aquatic life in general. The study of river hydrology and environmental flows often require the calculation of flow metrics (e.g., mean annual flow, flow duration statistics, low flow frequency analyses, etc.); however, uncertainties in these flow metrics have not been fully studied in the literature. The present study looks at uncertainties related to four flow metrics used in environmental flow studies using bootstrapping techniques for five hydrometric stations (located in the Miramichi River basin, Canada). The objectives of the study are: (a) to calculate and compare different flow metrics, (b) to carry out bootstrap samples in order to assess uncertainties as a function of sample size and (c) to determine which flow metrics are associated with the least uncertainty when calculating environmental flows using hydrological based methods. Results showed that uncertainties rapidly decreased from a 5‐ to a 15‐year sample size for each flow metric. The uncertainties from a 15‐ to a 50‐year sample size decreased, but not as rapidly as from a 5‐ to a 15‐year sample. The mean annual flow metric showed the least variability. For monthly flow metrics, sample sizes of 25–30 years were needed to obtain similar coefficients of variation as the 5‐year sample size of the mean annual flow. Drainage area did not impact the mean annual flow metric; however, uncertainty was observed to vary more significantly for smaller rivers on a monthly basis.

中文翻译：

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与环境流量指标相关的不确定性

在世界范围内，对河流取水的需求持续增长，这些取水通常会影响鱼类的栖息地和水生生物。对河流水文和环境流量的研究通常需要计算流量指标（例如，平均年流量，流量持续时间统计数据，低流量频率分析等）；然而，这些流量指标的不确定性尚未在文献中得到充分研究。本研究着眼于与使用五个水文站（位于加拿大Miramichi流域）的自举技术的环境流量研究中使用的四个流量指标相关的不确定性。研究的目标是：（a）计算和比较不同的流量指标，（b）进行bootstrap样本，以便评估作为样本量的函数的不确定性，以及（c）确定在使用基于水文学的方法计算环境流量时哪些流量度量与不确定性最小相关。结果表明，每种流量指标的不确定性从5年样本量迅速减少到15年样本量。从15年到50年的样本量的不确定性降低了，但没有从5年到15年的样本的不确定性快。年平均流量指标显示出最小的变化。对于月流量指标，需要25-30年的样本量才能获得与5年平均年流量样本量相似的变异系数。流域没有影响平均年流量指标；但是，观察到较小河流的不确定性每月变化更大。