内陆河高寒山区流域分布式水热耦合模型(Ⅰ):模型原理

A Distributed Water-Heat Coupled (DWHC) Model for Mountainous Watershed of An Inland River Basin(Ⅰ): Model Structure and Equations

在全球变暖的背景下，我国多数大江大河源区存在冰川退缩、雪线上升以及多年冻土和季节冻土明显退化等现象，并由此造成河源区产流量减少以及生态环境恶化等诸多问题，这在内陆河山区流域体现的较为明显，但目前分布式水文模型中很少涉及冻土水热耦合问题。文章以黑河干流山区流域为例，构建了一个内陆河高寒山区流域分布式水热耦合模型（DWHC）。模型基于土壤水热连续性方程将流域产流、入渗和蒸散发过程融合起来，在植被截留、入渗、产流和蒸散发计算方面也有所改进和创新。部分模块具有多个可选择方案。模型设计了与中尺度大气模式MM5的嵌套接口。也可以用地面气象资料驱动。模型在1km×1km网格基础上，以日为时间步长，将流域土壤分为18类，土壤剖面分为3～5层不等，流域植被概化为9类。模型只需要土壤初始含水量、初始地温和常规气象资料，以及土壤和植被物理参数，就能够连续演算各层土壤的温度、液态含水量、固态含水量、感热传导、潜热变化、水势梯度、导水率以及水分入渗和毛细上升量等水文循环要素。主要介绍了模型的基本原理和构建思路。有关模型的地面资料驱动结果和与MM5嵌套结果部分，参见后续文章（Ⅱ）、（Ⅲ）。

In the headwater regions of most large rivers in China, the glacier, permafrost and seasonal frozen soil have degraded largely, and the snowline has also risen in the recent 50 years, under global warming, especially in an inland river basin, where the main water resources come from mountainous river basin. Thus, it is very necessary to quantify the hydrological processes in these mountainous river basins, according to the fieldwork results and using hydrological modeling. However, the distributed hydrological model that describes the water-heat coupled processes is very rare, at the present time. Took the mountainous watershed of Heihe river basin, with an area of 10009km2, as an example, the authors designed a distributed water-heat coupled （DWHC） model. The minimal computing unit is a DEM （Digital elevation model） grid, with a spatial resolution of 1 km×1 km, and the reference frame is Alberts. The time step of the model is one day. The soil and vegetation of the watershed is divided into 18 and 9 types, respectively. In each computing grid, the soil is divided into 3 -5 layers, according to the landuse types. The DWHC model included 8 sub-models, which were meteorological model, vegetation interception model, snow and glacier melting model, soil water-heat coupled model evapotranspiration model, runoff production model, infiltration model and flow concentration model. The water-heat coupled processes, based on the continuous water and heat equation, runs through the runoff production processes, infiltration processes and evapotranspiration processes. The DWHC model gave a simple numerical solution to the continuous water and heat equation, according to the soil frozen states. The meteorological inputs are daily precipitation, daily averaged air temperature, and potential evapotranspiration, which come from the meteorological stations, or from the climatic models such as MM5. The soil and vegetation characters should also be described. At that time, the model could calculate the soil temperature, soil liquid water content, soil solid water content, sense heat, latent heat, soil water tension and runoff amount, etc. , given the initial soil water content and soil temperature. This paper just described the model principles, and the model results using the data at the meteorological stations as inputs, or using the MM5 results as inputs, would be discussed in the following papers.