Hydrological process research includes the study of precipitation interception, infiltration, runoff and evapotranspiration. There are many models of precipitation interception, which can be divided into statistical model, conceptual model and analytical model. The development direction of interception model is to establish a model with physical mechanism, which can fully reflect the precipitation interception process and reflect the influence of various factors on the interception process. After interception, the net precipitation reaching the ground enters the soil through the pores of the surface soil, and then permeates and diffuses along the soil pores to the deep layer. The development direction of seepage model is also to establish a model with physical mechanism, which can accurately describe the seepage process. However, there are many factors that limit the determination of such model parameters, such as the spatial heterogeneity of model parameters: in the horizontal direction, the soil infiltration capacity of different groups of vegetation, topography and other factors is also very different; In the vertical direction, the infiltration performance of each layer of soil, including the crust surface, is also different Ignoring these factors, the infiltration process obtained will be very different from the actual situation. Runoff can be divided into surface runoff, loam runoff and underground runoff according to the location. The main shortcomings of the existing runoff generation mechanism are: ignoring the influence of topographic slope and soil anisotropy on runoff generation, and paying insufficient attention to the role of unsaturated lateral flow in the formation of loam flow and groundwater flow. Evapotranspiration is another way of water loss in the system. Evapotranspiration includes plant transpiration and evaporation. There are many research methods of evapotranspiration, including hydrological method, micrometeorology method, physiological method, remote sensing method and simulation method of special purpose acquisition company, among which the physiological method measures the transpiration of plants.
The research of forest hydrology on soil moisture change belongs to morphological research, and the research on forest soil bulk density, porosity and other parameters and forest soil's ability to regulate water cycle is relatively few. Applying the theory of special purpose acquisition company and energy method to study soil moisture movement is the research direction that needs to be strengthened in forest hydrology in the future. There is no unified conclusion about the relationship between forest and rain. Most scholars believe that forests can increase horizontal precipitation, but have little effect on vertical precipitation, especially in a large range, but it does not rule out that they can affect atmospheric precipitation in a local range. Most scholars believe that forests can reduce flood volume, weaken peak flow and delay and prolong flood collection time, but this weakening effect is not infinite. The effect of forest on flood reduction is conditional, which is influenced by many factors, such as soil water content in the early stage, the degree to which litter layer is saturated by precipitation in the early stage, the intensity and duration of rainstorm, the topography of forest distribution, soil thickness and water permeability of underlying rocks, and the size of watershed. These will play a role in different degrees and cannot be generalized.
There are many studies on the influence of forests on water quality abroad. Since the mid-1980s, the research on forest and water quality has gradually become a hot spot, which not only studies the influence of forest on suspended sediment content in rivers, but also attaches great importance to the research on chemical factors and biological factors in forest and water quality. Forest and water interact and complement each other, so do forest hydrological processes and various ecological processes of forest ecosystem. In the past, the research on forest hydrology mainly considered the influence of forest vegetation and other factors on hydrological process, but paid insufficient attention to the ecological pattern and process of water affecting vegetation growth and distribution pattern, so it was impossible to comprehensively study the relationship between forest and water.