Abstract: The GIS-based long-term hydrological impact analysis (L-THIA GIS) model was used to simulatethe long-term impacts of urbanization on surface runoff in the Xitiaoxi River watershed in the upper reaches of Taihu Lake. Two historic land use scenarios (1985 and 2000) were analyzed to track land use changes in the watershed andto assessthe impacts of land use changes on annual average runoff. There was a 75% increase in urban land area from 1985 to 2000; consequently, the runoff coefficient increased by 1.4%. When the total urban area occupied was assumed to be 25% or 45% of the entire watershed, the runoff coefficient reached 0.68 or 0.79, respectively. Therefore, a reasonable urban land use plan is needed to limit blind urban expansion; the curve number should be used as an index in land use planning.

Key words: L-THIA GIS, surface runoff, land use change, scenario, Xitiaoxi River watershed

摘要： 利用基于GIS平台的长期水文影响模型(long-term hydrological impact analysis, L-THIA GIS)，选取太湖上游的西苕溪流域作为研究区域，在验证L-THIA模型在该流域径流模拟有效性的基础上，利用不同时期(1985年和2000年)土地利用状况变化分析城市化对径流的影响；并应用情景分析的方法预测未来不同的土地利用变化所导致的径流变化情况。研究结果表明：城镇用地产生的径流量要大于非城镇用地；1985?2000年城市建设用地面积扩张75%，径流系数相应增加了1.4% ；未来城市建设用地的不断扩张；当城市面积分别达到流域面积的25%和45%时，径流系数将可能达到0.68和0.79。因此，城市扩张导致的不透水面积的增加将成为改变区域水文效应主要因素之一，需要进行合理的城市和土地利用规划限制城市的盲目扩张。

关键词: L-THIAGIS, 径流, 土地利用变化, 情景分析, 西苕溪流域