Evaluating Estimates of Channel Flow in a Continental-Scale Lake-Dominated Basin Journal of Hydraulic Engineering

Accurate estimates of continental-scale channel flows are needed to understand spatiotemporal variability in water supplies and the water balance. At regional scales, models of connecting channel flows are commonly used to understand how variability in the water cycle propagates into engineering-oriented decisions related to water quantity and water quality management. Since 1958, deterministic monthly flows have been calculated for all of the connecting channels of the Great Lakes–St. Lawrence River system through a binational, multiagency coordination process. This article provides a review of these historical estimates, most of which have never appeared (or appeared decades ago) in the peer-reviewed literature, and compares them to new estimates from a novel statistical water balance model. This new model was developed using a variety of water balance component estimates across the entire Great Lakes system and includes an explicit expression of uncertainty. The findings of this research indicate that the historical range of deterministic channel flow estimates is similar to the range of uncertainty represented by the authors’ statistical water balance model. Findings also indicate that historical internationally coordinated flows for this massive lake and river system from the late 1990s through 2009 appear to be negatively biased and may need to be revised. The proposed statistical water balance model provides an ideal platform for implementing this revision and other future updates to regional water balance information.

精准测算大陆尺度河道流量(continental-scale channel flows)，是解析水资源供给与水量平衡(water balance)时空变异性(spatiotemporal variability)的核心需求。在区域尺度下，连通河道流量模型常被用于解析水循环变异性如何传导至与水量、水质管理相关的工程决策环节。自1958年起，依托两国多部门协同机制，研究人员已对五大湖-圣劳伦斯河系统(Great Lakes–St. Lawrence River system)的全部连通河道开展了确定性月均流量测算。本文对这些历史测算成果进行了系统梳理——其中多数内容从未（或仅在数十年前）在同行评议文献(peer-reviewed literature)中发表，并将其与一款新型统计水量平衡模型产出的最新测算结果进行了对比。该新型模型依托覆盖整个五大湖系统的多类水量平衡组分测算结果构建，并纳入了不确定性的显式表达。本研究结果显示，历史确定性河道流量测算的波动区间，与本文作者提出的统计水量平衡模型所表征的不确定性区间基本一致。研究同时发现，1990年代末至2009年间，针对这一巨型河湖系统的国际协同历史流量测算结果存在负偏差，或需进行修正。本次提出的统计水量平衡模型，可为该修正工作及未来区域水量平衡信息的其他更新工作提供理想的技术支撑平台。