Value of river discharge data for global-scale hydrological modeling
Value of river discharge data for global-scale hydrological modeling
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DOI：
10.5194/hess-12-841-2008
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发表时间：
2007-11
影响因子：
6.3
通讯作者：
M. Hunger;P. Döll
中科院分区：
文献类型：
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作者：
M. Hunger;P. Döll
抽象。本文探讨了观测到的河流流量数据的价值，为全球尺度的水文模拟的一些流量特性，例如需要评估水资源，洪水风险和水生生态系统的栖息地改变。WaterGAP全球水文模型（WGHM）的改进版本进行了调整，对测得的流量使用724站数据集（V1），对以前的模型版本进行了调整或扩展数据集（V2）的1235站。WGHM通过调整影响陆地产流的一个模型参数（γ）进行调整，以拟合调谐站的模拟和观测长期平均流量。在γ不足以调整模型的流域中，连续应用两个校正因子：面积校正因子校正流域中的局部径流，站点校正因子直接调整流量计。使用测站校正是不利的，因为它使流量在水位计处不连续，并且与上游流域的径流不一致。研究结果如下。(1)与V1相比，V2的全球陆地面积增加了5%，仅通过调整γ就可以调整模型的面积增加了8%。然而，必须应用测站校正因子（而不仅仅是面积校正因子）的区域增加了一倍以上。(2)WGHM的长期平均流量（以及可再生水资源）的空间分布的附加流量信息的价值很高，特别是对于V1调谐区域以外的流域，以及精细数据集提供了以前扩展的调谐流域（平均V2流域大小小于V1流域大小的一半）的显着细分的区域。如果额外的流量信息不用于调整，模拟的长期平均流量将不同于观察到的一个因素，平均而言，1.8在以前未调整的流域和1.3在细分的流域。在半干旱和降雪为主的地区，这种效益往往较高，因为在这些地区，模型的可靠性低于潮湿地区，而精确的调整补偿了气候输入数据的不确定性和WGHM尚不能代表的水循环的具体过程。对于其他流量特征，如低流量，年际变化和季节性，模拟值和观测值之间的偏差也显着减少，但这主要是由于更好地代表平均流量，而不是变率。(3)用于调整的最佳子流域大小的选择取决于建模目的。虽然超过60 000 km2的流域表现最好，但V2模型性能的改善在9000至20 000 km2之间的小流域中最强，这主要与低水平的V1性能有关。增加调谐站的密度提供了一个更好的空间表示的流量，但它也降低了模型的一致性，几乎一半的流域低于20 000平方公里需要站校正。
Abstract. This paper investigates the value of observed river discharge data for global-scale hydrological modeling of a number of flow characteristics that are e.g. required for assessing water resources, flood risk and habitat alteration of aquatic ecosystems. An improved version of the WaterGAP Global Hydrology Model (WGHM) was tuned against measured discharge using either the 724-station dataset (V1) against which former model versions were tuned or an extended dataset (V2) of 1235 stations. WGHM is tuned by adjusting one model parameter (γ) that affects runoff generation from land areas in order to fit simulated and observed long-term average discharge at tuning stations. In basins where γ does not suffice to tune the model, two correction factors are applied successively: the areal correction factor corrects local runoff in a basin and the station correction factor adjusts discharge directly the gauge. Using station correction is unfavorable, as it makes discharge discontinuous at the gauge and inconsistent with runoff in the upstream basin. The study results are as follows. (1) Comparing V2 to V1, the global land area covered by tuning basins increases by 5% and the area where the model can be tuned by only adjusting γ increases by 8%. However, the area where a station correction factor (and not only an areal correction factor) has to be applied more than doubles. (2) The value of additional discharge information for representing the spatial distribution of long-term average discharge (and thus renewable water resources) with WGHM is high, particularly for river basins outside of the V1 tuning area and in regions where the refined dataset provides a significant subdivision of formerly extended tuning basins (average V2 basin size less than half the V1 basin size). If the additional discharge information were not used for tuning, simulated long-term average discharge would differ from the observed one by a factor of, on average, 1.8 in the formerly untuned basins and 1.3 in the subdivided basins. The benefits tend to be higher in semi-arid and snow-dominated regions where the model is less reliable than in humid areas and refined tuning compensates for uncertainties with regard to climate input data and for specific processes of the water cycle that cannot be represented yet by WGHM. Regarding other flow characteristics like low flow, inter-annual variability and seasonality, the deviation between simulated and observed values also decreases significantly, which, however, is mainly due to the better representation of average discharge but not of variability. (3) The choice of the optimal sub-basin size for tuning depends on the modeling purpose. While basins over 60 000 km2 are performing best, improvements in V2 model performance are strongest in small basins between 9000 and 20 000 km2, which is primarily related to a low level of V1 performance. Increasing the density of tuning stations provides a better spatial representation of discharge, but it also decreases model consistency, as almost half of the basins below 20 000 km2 require station correction.