PHREEQC is a computer software (Parkhurst and appelo, 1999) for the calculation of various low-temperature hydrogeochemical reactions. PHREEQC, based on the ion linked water model, can (1) calculate the species and saturation index of matter formation; (2) simulate geochemical inversion process; (3) calculate batch reaction and one-dimensional migration reaction. In addition, PHREEQC coupled with multi-component solute transport model can generate PHAST, a three-dimensional reaction transport simulator for simulating groundwater flow system. PHREEQC is also useful in the investigation of unpolluted and polluted environment, laboratory, field and regional investigation. PHREEQC can investigate various natural and human influenced environmental geochemical reactions, including acid mine water discharge, radioactive waste isolation, pollutant migration, nutrient enrichment, aquifer natural and artificial restoration, aquifer reserve recovery, drinking water treatment, indoor experiment and regional aquifer system. PHREEQC has two graphical user interfaces available. Phreeqcl is a screen driven interface that provides a descriptive explanation for each data item (Charlton and Parkhurst, 2002). PHREEQC used in windows is a row editing object interface. Its additional input features enable it to generate graphic simulation results (post, 2004). 　

MODFLOW is a three-dimensional finite difference groundwater model. It uses modular structure, which makes it easy to modify to adapt to specific application code. Modflow-2000 simulates stable and unsteady flow in irregular flow systems. Aquifers can be closed or unclosed, or a combination of the two, flowing under external pressure, such as flowing to wells, surface recharge, evaporation, flowing to drainage channels, and flowing through riverbed. In addition to simulating groundwater flow, some related functions are extended, such as sediment transport.

Distributed hydrological model, water and energy prediction, geotop can be applied to very complex terrain, and integrates all surface energy balance conditions except water balance. For saturated and unsaturated subsurface flow, 3D Richard equation is adopted to realize accurate input of radiation parameters to obtain surface temperature.

Simulating the change of alluvial channel in drought

WOFOST is a single site simulation system developed by Wageningen University in the Netherlands. A dynamic interpretative model based on process was developed to simulate crop growth process under the influence of climate and other environmental factors (such as soil water and fertilizer), such as photosynthesis, respiration, transpiration, leaf area change, dry matter distribution and yield formation. The model can simulate crop growth process and crop yield under three conditions: sufficient water and fertilizer supply (potential growth condition), water limitation (rain fed condition) and nutrient limitation (insufficient supply of N, P, K).