A nonparametric kernel estimation model is proposed and developed for estimating low flow quantiles. Based on annual minimum low flow data and Monte Carlo simulation tests, the descriptive and predictive ability of the proposed model is compared with that of Weibull models. The results indicate that it has small bias and root mean square error in low flow quantile estimates. Application of the model to data from the Blue Nile has shown that the nonparametric approach is a viable alternative to the Weibull models.

A two-parameter monthly water balance model is developed. The model is used to simulate the runoff of seventy subcatchments in the Dongjiang, Ganjiang and Hanjiang Basins in the south of China. Application results show that the model efficiencies are high in both the calibration and erification periods. Comparative study of monthly water balance models indicates that the proposed two-parameter model as well as a five-parameter model performs. It is suggested that this twoparameter model can be easily and efficiently incorporated in the water resources planning program and the climate impact studies to simulate monthly runoff conditions in the humid and semi-humid regions.

本文综述陆地表面水文过程，大尺度水文模型及其与气候模型联结耦合研究的最新进展和存在问题，介绍GEWEX-GAME研究项目的目标和内容，科学价值和现实意义及其在我国开展研究的计划。

在全面综述分析国内外文献的基础上，提出和建立了一个基于DEM的分布式流域水文物理模型，并用来模拟小流域的降雨径流时空变化过程，得到了较好的模拟结果。论文分为模型结构和应用检验两部分。本文论述模型结构和数值解法，详细分析植物截留，蒸散发，融雪，下渗，地表地下径流方向和洪水演进等水文物理过程。

Climatic change has great implications for hydrological cycle and water resources planning. In order to assess this impact, a macro-scale and semi-distributed monthly water balance model was proposed and developed to simulate and predict the hydrological processes. GIS techniques were used as a tool to analyze topography, river networks, land-use, human activities, vegetation and soil characteristics. The model parameters were linked to these basin characteristics by regression and optimization methods. A parameterization scheme was developed and the model parameters were estimated for each grid element. Based on the different GCM and RCM outputs, the sensitivities of hydrology and water resources for China to global warming were studied. The proposed models are capable of roducing both the magnitude and timing of runoff and water resources conditions. The semi-dry regions, such as Liaohe, Haihe, Ruanhe and Huaihe River basins in north China, The runoffs of these basins are small or even zero during dry season (from Oct. to May) and are very sensitive to temperature increase and rainfall decrease. While in the basins of the humid south China like Yangtze River basin, the runoffs are perennial and the base flow normally occupies a large portion of the total runoff volume. These humid basins are less vulnerable to climate change. Results of the study also indicated that runoff is more sensitive to variation in precipitation than to increase in temperature. Climate change challenges existing water resources management practices by additional uncertainty. Integrated water resources management will enhance the potential for adaptation to change.