气候变化情景下青山湖流域的氮负荷时空分布预测研究

Temporal and Spatial Distribution of Nitrogen Load in Qingshan Lake Watershed under the Condition of Climate Changing

针对目前流域非点源污染,特别是不断增加的氮污染负荷问题,文章利用SWAT模型,将青山湖流域划分为46个亚流域、189个HRU,并使用2005-2011年的日尺度实测流量与主要降雨月份2011年7-8月的日尺度实测氮素浓度对模型参数进行率定,构建了青山湖流域氮素面源污染估算模型。利用所建模型,在气候变化情景下预测2030年氮负荷的时空分布特征,结果表明:(1)时间上,未来年均径流量提高了12.43%,且氮素流失的月变化特征明显,以NO_3^--N为主要流失形式,流失量主要集中在7-9月,占年总流失量的比例为52.67%;(2)空间上,氮素流失依然主要集中在流域中部和东南部农田比例较高的子流域。流域西北部的自然林地区的氮素流失负荷虽然保持较低的NO_3^--N流失量,但会有一个相对比较大的增幅,增幅量为13.5%。

In the context of the current issues of watershed non-point source pollution,especially the continuous increasing of nitrogen pollution load, SWAT model was used to divide Qingshan Lake watershed into 46 sub-basins and 189 hydrological response units and further constructed nitrogen non-point source pollution model of the watershed which was calibrated and verified with daily flow measurement during 2005-2011 and daily nitrogen concentration measurement during July and August,2011. Afterwards,the constructed model was applied to predict temporal and spatial distribution characteristics of the nitrogen load in the future（2030） under the condition of climate changing. Results showed that on the temporal scale,annual average runoff increased by 12.43% in the future,and monthly variation characteristics of nitrogen loss in the future were significant,mainly in the form of NO_3^--N. Nitrogen loss concentrated on the period of July to September was 52.67% of the yearly total loss. In the spatial scale,nitrogen loss was still mainly concentrated in some subwatershed of the central basin and southeastern basin where farmland is the dominant land-use type. The loss of NO_3^--N load in northwest region（mostly covered by natural forests）still kept lower,but a relative large increase of 13.5% would occur.