中文摘要：

计算效率的限制已成为目前阻碍分布式流域水沙模型发展的重要瓶颈之一,而并行计算方法则是当前提高模型计算效率的一种最有效的手段。针对国内外目前在流域水沙过程并行计算理论方面研究的不足,借助河网二叉树结构特征,提出了对流域水沙运动过程在时间域和空间域双重层面上进行离散的并行计算方法（时空双重离散法）,并对该方法进行了初步的理论分析。分析结果表明,相对于传统单纯的空间离散法,时空双重离散法在理论上可以显著提高并行计算效率,更有利于计算机资源的高效利用;同时发现对于任意的流域河网结构,在确定的计算时间范围内,时空双重离散法存在极限加速比,并推导出了通用的流域河网极限加速比公式;其中,极限加速比是流域河网的固有属性,主要取决于河网结构本身,它反映了分布式模型对流域水沙运动过程进行并行计算的效率上限,该指标可用来估算模型计算时间。

英文摘要：

Restricted computational capacity has become a key factor hindering the development of majority of distributed hydrological and soil erosion models. Parallel computing is one of the most effective approaches for solving this problem. Based on the binary-tree structure of drainage network,a kind of temporal-spatial-discrete approach was put forward for the parallel simulation process of river basin,and the preliminary theoretical analysis of the approach was performed. The approach enriches the parallel-computing theory of river basin. Comparing with the pure spatial-discrete approach at present,the temporal-spatial-discrete approach is capable of enhancing computational speed significantly and taking full advantage of computer resources. Moreover,with respect to an arbitrary drainage network of river basin,there exists ultimate speedup ratio （USR） under the proposed temporal-spatial-discrete approach,and the general formula calculating USR of river basin is given as well. USR is an inherent property of river basin and can reflect the efficiency upper bound of parallel computing for river basin.