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| 面向水文过程模拟的DEM子流域划分优化方法 |
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朱旭, 周玉良, 周平, 吴成国, 崔毅, 张宇亮
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合肥工业大学土木与水利工程学院
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| 摘要: |
| 为解决直接利用原始DEM提取的模拟河网不准确,与实际水系存在偏差,进而影响子流域划分的问题。论文基于区域实际影像,先通过区域实际影像中的河流位置,降低河道所在栅格的原始DEM的高程值；采用避免河网提取阈值选取主观性的河网密度法确定河源的最佳集水面积阈值；后设置不同的子流域集水面积阈值,通过阈值与子流域数量之间的关系,确定合适的子流域集水面积阈值和子流域数量；最后通过3种不同子流域划分方案下分布式模型的水文过程模拟结果,比较验证子流域划分的合理性。桃溪流域应用结果表明:先在GIS中对实际水系主河道经过的DEM栅格的高程降低40 m,再基于河网密度法确定的河源最佳集水面积阈值0.81 km2,提取出的河网更加贴近实际；当子流域集水面积阈值为108~144 km2时,桃溪流域被划分的子流域数量均为7个,平均面积为213.19 km2,划分的子流域面积与我国一级小流域范围标准(50~300 km2)一致。记实际水系主河道经过的DEM栅格高程降低40 m后划分的7个子流域、11个子流域分别为方案A和B,由原始DEM划分的7个子流域为方案C,比较桃溪流域在3种方案下应用三水源新安江模型的分布式模拟效果,其模型参数采用遗传算法率定,结果表明:在日径流模拟中,以1982—2012年为训练样本,2013—2022年为验证样本,训练样本日径流模拟的确定性系数分别为0.87、0.87、0.86,验证样本分别为0.9,0.91,0.9,3个方案的模拟精度基本一致；选取1982—2021年内20场最大洪水过程进行模拟,前15场为训练样本,后5场为验证样本,以洪峰、洪量和峰现时间为精度评定指标,A、B、C方案的合格场次分别为19、19、16场,合格率分别为95%、95%、80%；A、B、C方案在20场洪水过程模拟平均确定性系数分别为0.93、0.94、0.93,以确定性系数为精度评定指标,方案A中甲、乙级分别为16、4场；方案B中甲、乙级分别为18、2场；方案C中甲、乙级分别为18、2场。综上,根据实际水系,降低河流主河道经过的DEM栅格的高程进行分布式洪水过程模拟比未处理DEM栅格高程合格率更优,并且按照一级小流域面积范围将桃溪流域划分7个子流域相较于11个子流域,在确定性系数等精度上相差不大。研究方法可为分布式水文模型的构建以及其它相似条件下的子流域划分提供参考。 |
| 关键词: 流域划分 河网提取 河网密度法 集水面积阈值 DEM GIS 实际水系 桃溪流域 |
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| 基金项目:国家自然科学基金项目(42271084, 52379006, 52209011),国家重点研发计划项目(2023YFC3206604-02),安徽省自然科学基金(230808US13, 2208085QE179)资助。 |
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| Sub-watershed division based on DEM and actual river system and its application in hydrological process simulation |
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Zhu Xu, Zhou Yuliang, Zhou Ping, Wu Chengguo, Cui Yi, Zhang Yuliang
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College of Civil Engineering,Hefei University of Technology
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| Abstract: |
| To solve the problem that the simulated river network extracted directly from the original DEM is not accurate, deviates from the actual water system, and affects the sub-basin division. This paper based on the actual imagery of the region, firstly, lowers the elevation of the original DEM through the actual river positions in the regional actual imagery; secondly, determines the optimal watershed area threshold of the river source by the river network density avoiding subjective threshold selection; thirdly, sets different sub-basin watershed area thresholds, and determines the appropriate sub-basin watershed area threshold and the number of sub-basins through the relationship between the threshold and the number of sub-basins; finally, by comparing the hydrological process simulation results of the three different sub-basin division schemes, the scientificity of the sub-basin division is verified. Taoxi watershed is located in Shucheng County, Lu "an City, Anhui Province.The application study in Taoxi River Basin shows that: in GIS, the elevation of the DEM grid passing through the actual water system is lowered by 40 m firstly, and then the optimal watershed area threshold determined by the river network density avoiding subjective threshold selection is 0.81 km2, the extracted river network is closer to the actual; the number of sub-basins in Taoxi River Basin is divided into 7 by setting the threshold interval of 108~144 km2, the average area is 213.19 km2, the sub-basin area division is consistent with the standard of the first-class small watershed range in China (50~300 km2). Comparing the distributional simulation of Taoxi River basin under three schemes A, B, and C, which were divided into 7 sub-basins and 11 sub-basins after the DEM grid elevation was lowered by 40 m along the main river channel and the original DEM, respectively, and the model parameters were calibrated using a genetic algorithm, the results show that: in daily discharge simulation, with 1982—2012 as the training sample and 2013—2022 as the validation sample, the deterministic coefficient of the training sample discharge simulation was 0.87, 0.87, and 0.86, and the validation sample was 0.9, 0.91, and 0.9, and the simulation accuracy of the three schemes was basically consistent; selecting 20 maximum flood processes within the period of 1982—2021 for simulation, peak discharge, discharge volume, and peak occurrence time were used as accuracy evaluation indicators, and the qualified occasions of schemes A, B, and C were 19, 19, and 16, respectively, with qualified rates of 95%, 95%, and 80%; the average deterministic coefficient of the 20 flood process simulations for schemes A, B, and C were 0.93, 0.94, and 0.93, respectively, and the accuracy evaluation indicators of the first and second grades for schemes A were 16 and 4, respectively; the first and second grades for schemes B were 18 and 2, respectively; and the first and second grades for schemes C were 18 and 2, respectively. In summary, according to the actual river system, dividing the river basin into 7 sub-basins after lowering the elevation of the DEM grid along the main river channel can improve the qualified rate and the accuracy of the simulation, and dividing the Taoxi River basin into 7 sub-basins according to the area range of the first-order sub-basin is similar in terms of the deterministic coefficient and other accuracy indicators compared with dividing it into 11 sub-basins. The research method can provide reference for the construction of distributed hydrological models and the division of sub-basins in similar conditions. |
| Key words: watershed division river network extraction river network density method catchment area threshold DEM GIS actual water system Taoxi watershed |
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