Application Of The Climatic-hydrological Model ABCD With Investigations On Its Parameterization Properties

ABCD model is a climatic-hydrological model proposed by Thomas from the USA, which has only 4 parameters(a, b, c, d), using precipitation and potential evapotranspiration as input and estimating evapotranspiration, runoff as well as the changes in soil water and groundwater storage. It is available in modeling catchment hydrology by month step or annual step.In this paper, the ABCD model was applied to study hydrological climate response properties in multiple watersheds. The first case was the North Loup River Basin(NLRB) in Nebraska, USA, where meteorological and hydrological data are available for a long period more than 60 years.According to sensitivity analysis, the reasonable ranges of the initial storages and parameters were determined. It was found that the errors in the initial storages only significantly affect the estimation results for the beginning 10 years.Then the observation data in the un-sensitive period was applied to calibrate the model parameters. The changes of groundwater storage that obtained with the model basically agreed with the results in the literature estimated with groundwater level data. It indicated that the ABCD model is suitable for the North Loup River Basin. With theextreme drought and extreme humid climate conditions corresponding to the 50-year return period, the possible hydrological changes in catchment was forecasted by ABCD model.The results indicate that the soil water storage can quickly respond on the climate change has little buffer action on runoff. On the contrary, groundwater storage exhibited a delayed respond on the climate change and the half-life time is longer than 10 years, significantly reducing the runoff’s sensitivity to extreme climate.The second case was the Hailiutu River Basin in Ordos, China.The changes of baseflow that obtained with the model basically agreed with the results in the literature.It indicated that the ABCD model is also suitable. Responding to extreme climate scenarios in the catchment was basically identical with the previous case, and groundwater storage exhibited a more delayed respond on the climate change. The potential falw of the ABCD model is not considering groundwater evaporation, which can’t fully reflect the characteristics of the ordos plateau.With the background of the ordos plateau, this paper adopted the comparison between HYDRUS model and ABCD model to study the variables and the physical significances of the parameters in ABCD model. The results in daily step of the Soil-Plant-Atmosphere Continuum(SPAC) simulated by HYDRUS-1D were considered as the actual evapotranspiration. Using the ABCD model fitting the actual evapotranspiration in monthly and annual steps, the simulated results of soil water storage and leakage can be evaluated. The results indicate that ABCD model calibrated by actual evapotranspiration can’t obtain the leakage and soil water storage changes in monthly scale. In annual scale, it can model the leakage approximately, but soil water storage changes can’t be simulated. The simulation results of evapotranspiration by ABCD model have certain correlation with the soil hydraulic parameters(saturated moisture content ?s, residual moisture content ?r, saturated permeability coefficient Ks, curve parameters ? and n). The inversion results of ABCD model mainly depend on the parameter values of a and b. The correlation between the two parameters and traditional hydrogeological parameters were also analyzed.