DR3M

DR3M is a watershed model for routing storm runoff through a Branched system of pipes and (or) natural channels using rainfall as input. DR3M provides detailed simulation of storm-runoff periods selected by the user. There is daily soil-moisture accounting between storms. A drainage basin is represented as a set of overland-flow, channel, and reservoir segments, which jointly describe the drainage features of the basin. This model is usually used to simulate small urban basins. Interflow and base flow are not simulated. Snow accumulation and snowmelt are not simulated. Input Parameters: aily precipitation, daily evapotranspiration, and short-interval precipitation are required. Short-interval discharge is required for the optimization option and to calibrate the model. These time series are read from a WDM file. Roughness and hydraulics parameters and sub-catchment areas are required to define the basin. Six parameters are required to calculate infiltration and soil-moisture accounting. Up to three rainfall stations may be used. Two soil types may be defined. A total of 99 flow planes, channels, pipes, reservoirs, and junctions may be used to define the basin. Output Parameters: The computed outflow from any flow plane, pipe, or channel segment for each storm period may be written to the output file or to the WDM file. A summary of the measured and simulated rainfall, runoff, and peak flows is written to the output file. A flat file containing the storm rainfall, measured flow (if available), and simulated flow at user selected sites can be generated. A flat file for each storm containing the total rainfall, the measured peak flow (if available), and the simulated peak flow for user-selected sites can be generated. Process: The rainfall-excess components include soil-moisture accounting, pervious-area rainfall excess, impervious-area rainfall excess, and parameter optimization. The Green-Ampt equation is used in the calculations of infiltration and pervious area rainfall excess. A Rosenbrock optimization procedure may be used to aid in calibrating several of the infiltration and soil-moisture accounting parameters. Kinematic wave theory is used for both overland-flow and channel routing. There are three solution techniques available: method of characteristics, implicit finite difference method, and explicit finite difference method. Two soil types may be defined. Overland flow may be defined as turbulent or laminar. Detention reservoirs may be simulated as linear storage or using a modified-Puls method. Channel segments may be defined as gutter, pipe, triangular cross section, or by explicitly specifying the kinematic channel parameters alpha and m.DR3M是一款流域水文模型，以降雨为输入项，可在由管网与（或）天然河道组成的分支系统中完成暴雨径流汇流演算。DR3M可对用户选定的暴雨径流时段开展精细化模拟，两场暴雨间歇期内置逐日土壤水量平衡核算流程。该模型将流域概化为坡面流、河道与水库单元的集合，以此完整刻画流域汇流特征。本模型通常用于小型城市流域的模拟，且未考虑壤中流与基流的模拟，也未涵盖积雪积累与融雪过程。 输入参数： 每日降水量、逐日蒸散发量与短历时降水量为模型必输参数。若启用优化率定选项，则还需短历时流量序列作为输入。上述时间序列数据均从WDM文件（WDM file）中读取。此外，需提供糙率、水力学参数与子流域面积以定义流域汇流特征。入渗计算与土壤水量平衡核算共需6个参数。模型最多可配置3个雨量站，支持定义2种土壤类型。流域概化最多可使用99个坡面、河道、管网、水库与汇流节点单元。 输出参数： 模型可将每场暴雨时段内各坡面、管网或河道单元的计算出流结果写入输出文件或WDM文件。输出文件还将输出实测与模拟的降雨、径流及洪峰流量汇总结果。此外，可生成平面数据文件，包含用户选定站点的暴雨降雨、实测流量（若有）与模拟流量；还可生成单场暴雨对应的平面数据文件，包含用户选定站点的总降雨量、实测洪峰流量（若有）与模拟洪峰流量。 计算流程： 产流组分包含土壤水量平衡核算、透水区域降雨产流、不透水区域降雨产流及参数优化模块。入渗与透水区域降雨产流计算采用Green-Ampt方程（Green-Ampt equation）。可启用Rosenbrock优化算法（Rosenbrock optimization procedure）辅助率定部分入渗与土壤水量平衡参数。坡面流与河道汇流演算均采用运动波理论（kinematic wave theory），提供3种求解方法：特征线法、隐式有限差分法与显式有限差分法。模型支持定义2种土壤类型，坡面流可设定为湍流或层流流态。滞洪水库可采用线性蓄量模型或改进Puls法进行模拟。河道单元可概化为排水沟、管网、三角形断面，或通过显式指定运动波河道参数α与m完成定义。