联合改进TOPMODEL和PDSI的半干旱区干旱评估模型构建

Construction of draught estimation model with combination of improved TOPMODEL and PDSI

针对近年来半干旱区春旱不断,严重影响粮食产量,而应用于半干旱区的分布式水文模型和干旱评估模型较少且普遍存在物理基础不强、通用性较差的现状,该文以松嫩平原北部半旱区典型流域为依托,研发半干旱区栅格型水文模型及旱情评估模型。该水文模型的产流过程是运用格子波尔兹曼方法(Lattice Boltzmann method,LBM)建立的非饱和带和饱和带水流运动数值模块,而汇流过程则运用LBM方法求解坡面和河道水流运动方程建立的汇流数值模块,在栅格区域内各模块按松散耦合方式构建了基于LBM的栅格型TOPMODEL(LBMGTOPMODEL)。从水文循环角度,结合水文模型LBMGTOPMODEL和帕默尔干旱指数(Palmer drought severity index,PDSI),通过模拟半干旱区典型流域洮儿河的水循环过程各要素的时空变化来建立半干旱地区的干旱评估模型。结果表明:由次洪模拟得径流相对误差绝对值平均值为4.45%、洪峰流量相对误差绝对值平均值为5.00%、确定性系数均值为0.76,可得构建的LBMGTOPMODEL水文模型能较好地模拟洮儿河流域水文循环过程;气象、补水、径流、失水和气候特征等气象水文常数均呈现出一定空间分布状态,其中气候特征常数分布在0~7.23,差异性明显;气象水文常数均值随着计算时段的取值而变化;应用构建的半干旱区评估模型对研究区的干旱情况进行了评估,评估结果与洮儿河流域实际情况接近;将构建的干旱评估模型评估的干旱情况和单一因素干旱指标降水距平指数计算的干旱情况与实际情况相对比,得出基于分布式水文模拟的PDSI指标能更好地反映水文过程中多种因素对干旱的影响和干旱的时空演变过程,为旱情评估提供参考。

The frequent occurrence of drought for the semiarid region in spring period in recent years seriously influences the grain production.Distributed hydrological model and draught estimation model for semiarid region are not well developed,and they are not physically-based and universal.In this study,grid hydrological model and draught estimation model for semiarid region were established based on the data of typical northern semiarid region of Songnen Plain.The runoff process was estimated by saturated and unsaturated zone flow model,which was established based on LBM method.For the flow confluence process,flow confluence numerical model was constructed by solving the slope and river flow equation with LBM method,and furthermore,LBMGTOPMODEL was built by means of loose coupling for each module in the grid areas.From the respective of hydrologic cycle,combining with hydrological model LBMGTOPMODEL and Palmer Drought Index(PDSI),draught estimation model for semiarid region was formed by simulating the temporal and spatial variation of parameters in the water circulation process of Taoer River,which is located in a typical semiarid region.The results showed that the average absolute value of the relative error of the 10-field flood simulation runoff was 4.45%,the average absolute value of the relative error of the flood peak flow was 5%,and the mean value of the deterministic coefficient was 0.76.It could be seen that the established LBMGTOPMODEL hydrological model could simulate the process of rainfall and runoff with a high accuracy.Meteorological hydrological constants such as meteorology,water supplement,runoff,water loss and climate characteristics showed a certain spatial distribution state.Among the meteorological hydrological constants,the spatial distribution of climatic characteristic constants was 0-7.23,which showed the most obvious difference.The average values of meteorological hydrological constants changed with the variation of selected computational time period.When the established draught estimation model was used to assess the draught condition of investigated area,the model estimation results were in accordance with the actual conditions of Taoer River basin.When the draught conditions estimated by the established draught estimation model were compared with the draught conditions evaluated by rainfall deviation index of single factor drought index and draught conditions of the actual situation,it could be concluded that PDSI index evaluated by the distributed hydrological model could well reflect the effects of various factors in the hydrological process on the drought and the temporal and spatial evolution process of drought.PDSI index evaluated by the distributed hydrological model could provide guidance for the draught condition assessment.