Abstract：
Intermittent rivers in semiarid and arid regions, constituting over half of the world\'s rivers, alternate the carbon cycle interactions among the biosphere, hydrosphere, and atmosphere. Inadequate quantification of flow duration and river water surface area, along with overlooked CO2 emissions from dry riverbeds, result in notable inaccuracies in global carbon cycle assessments. High-resolution remote sensing images combined with intensive field measurements and hydrological modelling were used to estimate and extract the flow duration, river water surface area and dry riverbed area of Huangfuchuan, an intermittent river watershed that acts as a major tributary of the Yellow River in semiarid Northwest China. CO2 emission rates and partial pressures in water and air across the watershed were in-situ measured. In 2018, the flow duration of Huangfuchuan increased from less than 5 days in the first-order tributary to 150 days in the sixth-order mainstream. River water surface area estimated by remote sensing extraction plus the hydrodynamic model simulation varied from 3.9 to 88.6 km2 under 5 %-95 % discharge frequencies. CO2 emissions from the water-air interface and dry riverbed in 2018 were estimated at 582.3 × 103 and 355.2 × 103 ton, respectively. The estimated total annual emission (937.5 × 103 ton) aligns closely with the range of emissions (67.3 × 103-1377.2 × 103 ton) calculated for the water-air interface alone, derived using DEM river length and hydraulic geometry method. This similarity can be attributed to the overestimation of flow duration and flow velocity, as well as the over- or under-estimation of river water surface area and slope. The new method proposed in this study has large potential to be applied in estimating CO2 emissions from data-scarce intermittent rivers located in mountainous regions and provides a standardized solution in the estimation of CO2 emission. Results of this research reveal the spatiotemporal distribution of CO2 emissions along an intermittent river system and highlight the substantial role of dry riverbed in carbon cycle.
摘要：
半干旱和干旱地区的间歇性河流，构成了世界上一半以上的河流，生物圈之间的碳循环相互作用交替，水圈,和氛围。对水流持续时间和河水表面积的量化不足，以及被忽视的干燥河床的二氧化碳排放，导致全球碳循环评估中存在明显的不准确性。高分辨率遥感图像结合密集的现场测量和水文建模被用来估计和提取流量持续时间，皇甫川的江面面积和干河床面积，中国西北半干旱的黄河主要支流，断断续续的河流流域。现场测量了整个流域的水和空气中的CO2排放速率以及分压。2018年，皇甫川的流量持续时间从一阶支流的不足5天增加到六阶主流的150天。在5％-95％的排放频率下，通过遥感提取和水动力模型模拟估算的河水表面积在3.9至88.6km2之间变化。2018年水-空气界面和干河床的CO2排放量估计为582.3×103吨和355.2×103吨，分别。估计的年总排放量（937.5×103吨）与仅针对水-空气界面计算的排放量范围（67.3×103-1377.2×103吨）非常吻合，利用DEM河流长度和水力几何方法推导。这种相似性可以归因于过高估计的流动持续时间和流速，以及河流水面面积和坡度的高估或低估。这项研究中提出的新方法具有很大的潜力，可用于估算山区数据稀缺的间歇性河流的CO2排放量，并为CO2排放量的估算提供了标准化的解决方案。这项研究的结果揭示了间歇性河流系统中CO2排放的时空分布，并强调了干河床在碳循环中的重要作用。
