The precise reproduction of different flow regimes in both gauged and ungauged watersheds is crucial for managing environmental flow and water quality requirements. However, the ability of hydrological models to reproduce flow quantiles (FQs) is often influenced by the process of calibrating the most dominant parameters through traditional parameter estimation methods. This research proposes a systematic parameter estimation approach to improve the credibility of the hydrologic model in reproducing FQs in gauged and ungauged watersheds through the following steps: (a) implementation of parameter sensitivity analysis to identify the dominant parameters, (b) initial estimation of the sensitive parameter values, (c) an iterative search for the optimal value of the dominant parameter in reproducing FQs and (d) regionalization of parameters to estimate FQs in the ungauged watersheds. The analysis shows the highest sensitivity of the runoff curve number (CN2) in simulating the hydrologic process in all test watersheds. Moreover, the best value of CN2 was found to be different for each flow quantile. Therefore, CN2 was updated for reproduction of FQs, which resulted in an overall average improvement of the regionalized model accuracy (across all test watersheds and flow quantiles) by 37 and 46% during the calibration and validation periods, respectively. The spatiotemporal dynamics of the water balance components that often control the behaviours of FQs in both the gauged and ungauged watersheds were also quantified. The results show a wide range of spatiotemporal variations for the majority of the water balance components.

中文翻译：

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在有规和无规盆地提高流量分位数预测可靠性的策略

在已规范和未规范流域中，精确再现不同流态对于管理环境流量和水质要求至关重要。但是，水文模型再现流量分位数（FQ）的能力通常受通过传统参数估计方法校准最主要参数的过程影响。这项研究提出了一种系统的参数估算方法，可通过以下步骤来提高水文模型在有规无规流域重现FQ时的可信度：（a）进行参数敏感性分析以识别主要参数，（b）初步估算敏感参数值 （c）迭代搜索再现FQ时占主导地位参数的最佳值，以及（d）参数的区域化以估计未启用流域的FQ。分析显示，在所有试验流域模拟水文过程时，径流曲线编号（CN2）的灵敏度最高。此外，发现每个流量分位数的CN2最佳值都不同。因此，更新了CN2以复制FQ，从而在校准和验证期间分别使区域化模型的准确性（在所有测试分水岭和流量分位数上）总体平均提高了37％和46％。还定量了经常控制在有标量和无标量的流域中FQ行为的水平衡成分的时空动态。