Algorithm model of continuous multi flow confluence

HYDRUS-1D model is a finite element model, which is used to simulate the one-dimensional motion of water, heat and multiple solutes in variable saturated media. The model solves Richards' saturated unsaturated water flow and Fickian based advection dispersion equations of heat and solute transport.

Topoflow is a powerful and spatially distributed hydrological model with a user-friendly click interface. Its main purpose is to simulate many different physical processes in a watershed, and its goal is to accurately predict how various hydrological variables will evolve in response to climate forces.

The process of energy flow and material circulation in the soil vegetation atmosphere system controls the microclimate environment of vegetation growth, which has an important impact on the growth of vegetation. At the same time, the exchange of energy and water between the surface and the atmosphere determines the intensity and stability of turbulence and diffusion in the boundary layer, and controls the lower boundary conditions of the climate system such as wind speed, temperature and humidity- Vegetation atmosphere transport model is very important to study and forecast climate change, hydrological cycle and ecological environment dynamics. J. W. Deardorff put forward the concept of "big leaf", added a layer of vegetation to the land surface simulation, and began to consider the ecological hydrological process of vegetation, thus forming the prototype of SVAT model. Isba is an interaction model among soil, biosphere and atmosphere, which was proposed by J. noilhan in 1989. It is used to simulate the exchange of heat, mass and momentum between land or water surface and upper atmosphere. The model is applied to the so-called independent development model. In the coupled model, the model provides lower boundary conditions for the atmospheric numerical weather forecast model, or higher boundary conditions for the distributed hydrological model.

Cxtfit is a computer software developed by the saline soil laboratory of the United States to study one-dimensional soil solute transport. Based on Levenberg Marquardt algorithm, cxtfit uses the function optimization method of nonlinear least square to fit the breakthrough curve of solute mixture replacement experiment, solves the model parameters, and predicts the concentration distribution of solute in soil with time and space. Cxtfit is based on the solute convection dispersion equation. The original cxtfit1.0 was developed and compiled by Parker and van Genuchten, and gradually improved into today's cxtfit2.0, which contains more equation analysis for different initial boundary value problems and generation problems. The software includes three different types of solute transport models: equilibrium CDE model, physicochemical nonequilibrium CDE model and stochastic flow tube model.

Glims model is jointly developed by University of Georgia and USDA-ARS, its predecessor is creams, which is mainly used for small-scale simulation. The water quality items that can be simulated include sediment, nitrate nitrogen, ammonia nitrogen, phosphorus nitrate, ammonia nitrogen, total nitrogen, total phosphorus, etc. The modified SCS curve number method was used to simulate rainfall runoff, and the priestly Taylor or penman Monteith method was used to simulate evaporation. By simulating the effects of ammoniation, nitrification, denitrification, volatilization, absorption and fixation, the nitrogen factor was simulated by combining empirical or semi empirical formula with the model. A long-term soil erosion model developed by Sharpley et al. Was used to simulate phosphorus. The pesticide composition was mainly aimed at the interaction of pesticide characteristics, soil texture, climate impact, management strategy, surface runoff leakage and adhesion. The model also simulated the pesticide transport in the rhizosphere.

Pihm is a physical model of land surface and groundwater, closely coupled to GIS interface. Pihmgis is open source, platform independent and extensible. Through the development of shared data model and hydrological model data structure, the close coupling between GIS and model is realized.