洪峰流量是水利工程规划设计、工程建设和运营管理的重要依据，对水利工程的投资规模和安全运行有着重要的意义。西藏地区主要水文测站实测洪峰流量（Instantaneous Peak Flow，简称：IPF）资料稀缺，而按水位计算整编的日径流资料（Mean Daily Flow，简称：MDF）相对较多。本文通过构建实测资料时段的洪峰流量与对应日平均流量间的函数关系，基于长序列的日径流资料估算洪峰流量，延长洪峰流量序列，为设计洪水提供数据支撑。研究结果表明：（1）：西藏地区主要水文测站IPF～MDF函数关系稳定，利用这种函数关系由实测MDF推求的IPF误差均在10%以内，且延长后的IPF序列频率分析计算结果更加合理。（2）对于实测MDF序列缺乏的测站，通过气象资料驱动HIMS系统水文模块（Hydro Informatic Modeling Systerm）拓展MDF序列，在此基础上推求IPF序列。基于HIMS 系统水文模块对西藏三条典型河流（年楚河、拉萨河和尼洋河）的日径流序列进行了模拟，结果表明：模型对日径流整体过程与高流量值的模拟效果均良好。进而利用模型延长的MDF序列以及构建的IPF～MDF函数关系拓展了西藏三条典型河流2000～2010年间的IPF序列。
The instantaneous peak flow (IPF) is the basic information for hydraulic design，construction and management. It also has an important influence on the investment and safety of hydraulic structures. However, the IPF records in Tibet are generally short in length, while mean daily flow (MDF) records are relatively longer. In this study, the IPF records are extended by analyzing the relationship between corresponding IPF and MDF records. The results show that the ratio between IPF and MDF is stable in most of hydrological stations. The relative error between estimated IPF and observed IPF is less than 10%. The results of flood frequency analysis using extended IPF series are more reasonable than that using the measured IPF series. For the stations with limited measured MDF, the HIMS model is used to extend the available MDF. The HIMS model is applied in three representative rivers of Tibet: the Nianchu river, Lhasa river and Niang river. The results show that the model has a good performance in both daily and peak flow simulation. The end year of IPF series in the three representative hydrological stations has been extended from 2000 to 2010 by the simulation results of HIMS and the relationship between IPF and MDF.