Long-term droughts observed in southern Australia have changed relationships between annual rainfall and runoff and tested some of the assumptions implicit in rainfall–runoff models used in these areas. Predictive confidence across these periods is when low using the more commonly used rainfall–runoff models. Here we modified the GR4J model to better represent surface water–groundwater connection and its role in runoff generation. The modified model (GR7J) was tested in 137 catchments in south-east Australia. Models were calibrated during “wetter” periods and simulation across drought periods was assessed against observations. GR7J performed better than GR4J in evaluation during drought periods where bias was significantly lower and showed improved fit across the flow duration curve especially at low flows. The largest improvements in predictive performance were for catchments where there were larger changes in the annual rainfall–runoff relationship. The predictive performance of the GR7J model was more sensitive to objective function used than GR4J. The use of an objective function that combined daily and annual error produced a better goodness of fit when measured against 80, 50 and 20 percent excedance flow quantiles and reduced evaluation bias, especially for the GR7J model.

中文翻译：

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概念模型修改与澳大利亚东南部的千年干旱

在澳大利亚南部观察到的长期干旱改变了年降水量与径流量之间的关系，并检验了这些地区使用的降雨径流模型中隐含的一些假设。使用更常用的降雨－径流模型时，这些时期的预测置信度较低。在这里，我们修改了GR4J模型，以更好地表示地表水与地下水的联系及其在径流产生中的作用。修改后的模型（GR7J）在澳大利亚东南部的137个集水区进行了测试。在“较优”时期对模型进行了校准，并根据观测结果评估了干旱期间的模拟。在干旱期间，GR7J的表现要好于GR4J，在干旱时期，偏见显着降低，并且在整个持续时间曲线上显示出更好的拟合度，尤其是在低流量时。预测性能的最大改善是对年降雨量与径流量关系有较大变化的集水区。GR7J模型的预测性能比GR4J对使用的目标函数更敏感。当针对80％，50％和20％的流量流量分位数进行测量时，结合每日和年度误差的目标函数的使用会产生更好的拟合度，并降低评估偏差，尤其是对于GR7J模型而言。