LASCAM水文模型在流域生态水文过程研究中的应用——模型理论基础

LASCAM水文模型是一种大尺度分布式概念水文模型,介于高精度分布式水文模型和集总式经验模型之间,是基于亚流域空间单元建立的中等精度的分布式概念模型。LASCAM模型在亚流域空间单元定义了3个概念性土壤水库,在经验方程的基础上:①建立亚流域各土壤水库与亚流域生态特征(LAI)和气候(降雨)之间函数关系;②通过对亚流域的降雨-植冠截流过程、地表产流过程、表层入渗-亚表层产流过程、亚表层入渗过程的模拟,揭示降雨在亚流域的(地表和亚表层)径流和入渗等环节的再分配过程;③基于亚流域各土壤水库的水量(水位)建立了各土壤水库之间的水通量过程方程;④建立亚流域各库的蒸散发与生态特征(LAI)之间的函数关系模拟各库的蒸散发过程。最后,通过河道径流演算法则,并依据亚流域与流域总体之间的分布式关系,将各亚流域的径流汇总到整个流域,从而将亚流域空间的水文响应扩展到流域整体空间上,实现了大尺度异质性流域的水文过程和水量平衡模拟。

Application of LASCAM in Study on the Ecohydrological Processes of Catchment--Theoretical bases

LASCAM (Large Scale Catchment Model) is a kind of large-scale catchment hydrological model with intermediate resolution between the fully lumped conceptual hydrological model and the fully physically-based distributed hydrological model. LASCAM first develops the lumped conceptual model at all subcatchments which form the building blocks for the hydrological modeling of the whole catchment. Each subcatchment includes 3 conceptual soil water stores: A representing the near-stream perched aquifer, B representing the permanent deeper groundwater store, and F representing the intermediate unsaturated infiltration store. Water balance and water flux processes of and within each soil water store are the most important for model construction.Lumped conceptual model at subcatchment scale is the building block to the catchment model. Water levels of each soil water store will control the main water fluxes and other hydrological processes within the subcatchment. Based on empirical equations resulted from regional case studies in southwest area of the Western Australia, at the scale of each subcatchment, LASCAM: 1) first establishes the functional relationship between each soil water store and ecological (Leaf Area Index) and climatic characteristics (precipitation); 2) constructs a series functions to model precipitation interception through canopy, surface runoff generation processes, processes of surface infiltration and subsurface runoff generation, subsurface infiltration to F store, which unveil the reallocation processes of ground precipitation to runoff (including surface and subsurface) and infiltration within each subcatchment; 3) builds water flux processes between each soil water store based on their water quantity (water level); 4) builds the links between the evaporation of each soil water store and ecological characteristics (LAI) to model evaporation of each store. In the end, LASCAM integrates runoff generated in each subcatchment into the whole catchment through stream network routing subroutine and the distribution status of each subcatchment within the whole catchment, which makes it possible to model the hydrological processes and water balance of large-scale heterogeneous catchment.