A Study Of Time Variant Gain Model's Parameters Identification And Its Application In Ungauged Basins

Hydrology is a branch of geoscience,and nonlinear science is a comprehensive basic discipline that reveals the complexities of the earth system.The formation and transformation of runoff are hard to describe with linear theories.Due to the strong spatial-temporal changes in the underlaying surface and atmosphere,the nonlinear in hydrological phenomenas is promient,which bring a problem for flood forecasting.Reducing the uncertainty in hydrological forecasting is the core of prediction in ungauged basins(PUB)that aims to explore the new theoretical methods of hydrological forecasting to achieve a significant breakthrough in accuracy of PUB.The hydrological model based on physical process is one of the main solutions of PUB.The combination of hydrological physics and hydrological nonlinear system theories can help to explore the nonlinear mechanism of hydrological system,and establish a theoretical and practical hydrological system model.In this paper,a simple nonlinear system model is introduced,namely Time Vairant Gain Model(TVGM),which can be transformed into the complex nonlinear hydrological model.TVGM with less parameters has the advantages in PUB.This paper focuses on improving the technical methods of TVGM in PUB.The main research results and conclusions are summarized as follows:(1)The model construction and parameters identification of TVGM.In this paper,the recognition principle of parameters in TVGM based on the measured data is introduced in detail.And from the views of the hydrological system and hydrological physics,the method of parameters indentifications based on soil moisture constant is proposed.The relationship between model parameters and soil mositure constants is deduced.(2)The application and analysis of TVGM's parameters identification based on soil moisture constant in ungauged basins.The 15 different tested watersheds were selected,and the soil mositure constants of the watershed were obtained by extracting the soil information.Based on the expression between parameters and soil mositure constants established in the second chapter of this paper,the parameters of the hydrological model are calculated.The results show that the way is reasonable and feasible,and the simulation effect of TVGM with exponential structure is slightly better than that of binomial structure.(3)A Study on parameters regionalization of TVGM.The applicability of the TVGM in the tested watersheds was validated.The watershed attributes of topography,soil type and land use patterns related to parameters were extracted.Considering the physical meaning of parameters,the regression equations were constructed and verified.The study improves the TVGM's application in ungauged basins.