The Perturbed Rainfall Uncertainty Unit Hydrograph Method

The Unit Hydrograph (UH) theory can be used to estimate the discharge hydrograph of a basin based on precipitation and runoff measurements. However, uncertainty in those measurements may unable a unique UH to be derived. It is well known that in comparison with runoff measurements, the spatial and temporal variability of rainfall is the main source of uncertainty. Hence, in this work we present a method to derive an improved unique UH assuming that the rainfall data is the main source of uncertainty. The Perturbed Rainfall Uncertainty Unit Hydrograph (PeRUUH) method is verified using a large scale rainfall simulator (LSRS). The method combines linear programming and reverse modelling to generate a perturbed rainfall intensity pattern, which accounts for the temporal and spatial rainfall uncertainty assuming discharge to be true. The method is validated in three different rainfall events using the LSRS. The PeRUUH method is more robust than the original UH, as it is shown to be able to estimate a unique UH for which the discharges have an error of (approx.) 10 times smaller than its counterpart.单位线（Unit Hydrograph，UH）理论可基于降水与径流实测数据，推求流域的流量过程线。然而，实测数据的不确定性会导致无法推求出唯一的单位线。众所周知，相较于径流实测数据，降雨的时空变异性是不确定性的主要来源。因此，本研究提出一种改进的唯一单位线推求方法，假定降雨数据为不确定性的主要来源。扰动降雨不确定性单位线（Perturbed Rainfall Uncertainty Unit Hydrograph，PeRUUH）方法采用大型降雨模拟器（Large Scale Rainfall Simulator，LSRS）进行验证。该方法结合线性规划与逆向建模技术，生成扰动降雨强度模式，在假定流量实测值为真实值的前提下，考量降雨的时空不确定性。本方法借助LSRS，针对三场不同的降雨事件开展了验证。研究表明，PeRUUH方法的鲁棒性优于原始单位线方法，其可推求出唯一的单位线，对应的流量误差较传统方法缩小约10倍。