改进SWAT模型水库模块及其在水库控制流域径流模拟中的应用

为在径流模拟中充分考虑水库的综合调蓄作用，改善了SWAT（The Soil and Water Assessment Tool）模型的水库算法，在水库模块中增加基于水库供水发电调度规则的水库出流模拟算法，以提高径流模拟精度。选择东江流域作为典型流域，分别应用改进前后的SWAT模型进行径流模拟，并分析模型改进的效果，结果表明：修改后的SWAT模型解决了水库模拟出流量在非汛期过低、汛期过大的问题，能更有效地模拟枯季径流和洪峰流量，明显提高了月径流及日径流的模拟精度，其中，月径流模拟中率定期内R2提高了0.06~0.22，NS提高了0.06~0.52，验证期内R2提高了0.1~0.19，NS提高了0.12~1.22；日径流模拟中率定期内R2提高了0.04~0.16，NS提高了0.04~0.46，验证期内R2提高了0.11~0.15，NS提高了0.15~1.21。

Modification of Reservoir Module in SWAT Model and its Application of Runoff Simulation in Highly Regulated Basin

Humans have altered the water cycle with methods such as construction of dams. Large dams and reservoirs can significantly modify the natural flow within channels, as well as the distribution of water in the basin. This kind of changes will evidently affect the runoff simulation which is of high importance in many kinds of hydrological research issues. The Soil and Water Assessment Tool (SWAT), one of the most popular hydrological models over the world, was designed for use on rural basins, and only take simple human activities into account. The algorithm in the reservoirs module of SWAT was designed for those dams just with flood control needs, and it unavoidably made the model not suitable enough for such basins with highly regulated reservoirs, especially in the application at daily time step. To consider the operations of reservoirs in runoff simulation, a new algorithm for reservoirs with predefined complex operational rules was integrated into SWAT in this paper, and the rules adopted were designed for the benefits including water supply, electricity generation, and flood control. The paper was aiming at providing users of SWAT model with a simple and convenient way to deal with reservoirs in runoff simulation and improving the runoff simulation of SWAT model in regions with highly regulated reservoirs at both daily and monthly time steps. The performance of the modified model was tested at daily and monthly time steps over the East River (Dongjiang) Basin in China. After comparing the outputs of runoff simulation before and after modification, the results showed that the modified SWAT model could solve the problem that the simulated outflow of reservoirs had been too low in non-flood seasons and excessive in flood seasons before. Moreover it could work out a better output in runoff simulation at both monthly and daily time steps. The improvement of runoff simulation at the stations hugely impacted by dams was more remarkable. In addition, there is also an impressive result in the simulation of the water level in reservoirs. In terms of parameters, the sensitivities of SOL_K (Saturated hydraulic conductivity), SOL_AWC (Available water capacity of the soil layer) and GWQMN (Threshold depth of water in the shallow aquifer required for return flow to occur) became lower after modification. In details, at the monthly time step, the coefficient of determination (R2) was increased by 0.06~0.22 in calibration period and 0.1~0.19 in validation period , while the Nash-Sutcliff Efficiency (NS) was increased by 0.06~0.52 in calibration period and 0.12~1.22 in validation period after modification; at the daily time step, R2 was increased by 0.04~0.16 in calibration period and 0.11~0.15 in validation period, while NS was increased by 0.04~0.46 in calibration period and 0.15~1.21 in validation period after modification. Although the accuracy of the model is limited by the error in simulating the process upstream of the reservoirs, the improvement of the runoff simulation in the East River Basin is still significant after modification. Thus, it is a valuable reference for hydrological simulation in such watersheds that are hugely affected by reservoirs operations.