Global patterns in river water storage dependent on residence time

Earth’s rivers are the most sustainable source of freshwater, making accurate knowledge of global river flows and stores critical for informing water management1. However, previous estimates of global river flows are widespread1–16 and prior estimates of river stores are sparse17. Challenging accuracy, global estimates of river flows and stores are plagued by uncertainties in land runoff18, an unobserved quantity that provides water input to rivers. Here, we leverage global river flow observations to simultaneously correct continental runoff and river flow together, and further quantify river water storage, generating the first globally corrected monthly river flow and storage dataset. We estimate global river storage mean and monthly variability as 2165 ± 415 km3 and global continental flow as 37455 ± 6925 km3/yr. Our analysis reveals flow wave propagation time as an unexpected, but fundamental driver that can double or halve river water stores and their variability, while also reconciling past debates on global river flows. We identify previously underappreciated freshwater sources to the ocean in water discharged from the Maritime Continent (Indonesia, Malaysia, and Papua New Guinea) amounting to nearly 1.5 times the Congo River, and illustrate our capability to detect severe anthropogenic water withdrawals.

地球河流是最为可持续的淡水来源，因此精准掌握全球河流径流量与储水量，对水资源管理决策具有至关重要的指导意义¹。不过，此前针对全球河流径流量的估算存在诸多分歧¹–¹⁶，而关于河流储水量的相关研究则相对匮乏¹⁷。全球河流径流量与储水量的估算精度饱受质疑，这是因为陆地径流——这一无法直接观测的河流补水来源——存在不确定性¹⁸。本研究依托全球河流径流量观测数据，同步校正大陆径流与河流径流量，并进一步量化河流水储水量，构建了全球首套经过校正的逐月河流径流量与储水量数据集。本研究估算得到全球河流水储水量的均值与月际变幅分别为2165±415 km³，全球大陆径流总量为37455±6925 km³/年。分析结果表明，径流波传播时间是一项此前未被充分认知的关键影响因子——它可使河流水储水量及其变幅翻倍或减半，同时还解决了过往关于全球河流径流量的学术争议。本研究还发现了此前未得到足够重视的海洋大陆（Maritime Continent，即印度尼西亚、马来西亚与巴布亚新几内亚）入海淡水来源，其径流量近乎是刚果河的1.5倍；同时验证了本数据集可有效检测大规模人为取水活动。