Apex model includes nine modules: meteorology, hydrology, water erosion, nutrient, soil temperature, crop growth, cultivation, crop environmental management and economy. The improved SCS Runoff Curve number method is used to estimate the daily runoff of the model. The original SCS model provides the Runoff Curve Number with a slope of about 5%. The modified Runoff Curve number can be used for other slopes. At the same time, the daily runoff curve number is adjusted according to the soil moisture content and its distribution. Must equation is used to simulate water erosion, which is improved by musle. The biggest difference between must and USLE is that runoff and peak velocity are used as erosivity indicators to simulate soil erosion and sediment yield. This not only improves the prediction accuracy, but also avoids the use of sediment transport rate, but also can be used for sediment yield estimation of word rainstorm.

MM5 model has the main functions of non static dynamic frame, multi-layer grid nesting, various physical process options, four-dimensional variation, and more extensive computer platform transplantation. The simulation area of MM5 adopts Lambert projection, and the two true latitudes are 25 degrees north latitude and 40 degrees north latitude respectively. In order to ensure the accuracy of boundary meteorological field, MM5 simulation area has three grids more than the horizontal boundaries of air quality simulation area; the top of the simulation layer is 100MB, which is vertically divided into the following 23 σ layers. The data of terrain and surface type are global data of USGS; the objective analysis is based on the ADP global surface and high-altitude observation data of NCEP to conduct grid four-dimensional data assimilation. The parameterization of physical processes in the simulation domain are as follows: Kain Fritsch's cumulus parameterization scheme; pleim Xu's boundary layer and land surface parameterization scheme; Reisner's multiphase explicit water vapor scheme; cloud radiation parameterization method; and multi-layer soil model.

DRAINMOD is a computer simulation model, which simulates the hydrological conditions of poorly drained high water level soil hourly with a long climate record (for example, 50 years). The model predicts the impacts of drainage and related water management practices on groundwater table, soil moisture status and crop yield. The parallel method is mainly used to analyze the hydrological conditions of some types of wetlands to determine whether the wetland hydrological standards meet the requirements of drainage or part of the drainage site. The model is also used to determine the hydropower capacity of the sewage treatment system. The model has been successfully tested and applied to various geographical and soil conditions. Over the past 20 years, the model's capacity has been extended to predict the impact of drainage and water resource management practices on hydrology and water quality in farmland and watershed wide agriculture and woodland.

Soil crop simulation model has become an effective tool to provide scientific basis for agricultural production and management decision-making. APSIM model was developed by Australian scientists to simulate various biological processes in agricultural system. In particular, the mechanism model of ecological and economic output of each component of the system under climate risk. APSIM has been verified and applied in soils with temperate continental climate, temperate marine climate, subtropical arid climate and Mediterranean climate zone, including clay, expansive soil, deformable soil, silty sandy soil, silty loam and silty clay loam, which can be used to simulate more than 20 crops such as wheat. APSIM model has good ability to describe crop structure and crop rotation sequence adjustment, crop yield, quality prediction and control, and soil water flow imbalance control under different planting patterns.