Investigation of the scale-adaptive digital terrain analysis method for rainfall-runoff process modelling in the aridzone of China

The rapid growth of the world economy and population has created a great impact on the earth’s water cycle and water resources. Moreover, intensive human activities, such as the clearance of forests and expansion impermeable surfaces, have also made our living environment vulnerable and susceptible to extreme weather conditions. The hydrological cycle is a complex process. A better understanding of rainfall-runoff responses is a key issue for preventing and reducing natural disasters and for the better use of water resources. In an aridzone, runoff from mountainous region is essential for the survival of human settlements in the lower reaches. The rainfall-runoff often shows an unstable spatio-temporal pattern, largely due to variations in mountain topography. Because of water shortage and its influence on settlements, regional water resource studies often form a focus of hydrological modelling. Fewer investigations have looked at rainfall-runoff events, which may cause devastating consequences due to the poor water holding capability of the environment.

As is common with geographical problems, an understanding of the rainfall-runoff process also closely relates to the investigation scale. This study, therefore, will investigate methods for multi-scale hydrological modelling that are suitable for aridzone applications in China’s west. A 3-dimensional terrain-based hydrological process model will be developed by integrating a multi-scale digital terrain model with a topological flow-path network model, which is capable of representing complex hydrological processes by a set of flow tubes perpendicular to contours at a given investigation scale. Thus, the water movement over a 3-dimensional surface can be simplified and modelled to one dimension. Then a conventional one-dimensional formula in fluvial hydraulics can be linked to the flow path segments for dynamic event-based simulations. A software platform will be developed to implement the proposed spatio-temporal models to establish a ‘test-bed’ for the analysis of impacts of environmental variables and scales, and for better understanding about the hydrological processes in the aridzone of western China.

Answers will be sought for fundamental research questions in the aridzone hydrology including: (1) the topographic control on the spatio-temporal distribution of rainfall- runoff in the mountainous region, (2) the relationship between the runoff and other environmental variables in the aridzone, (3) the process of flow generation and convergence corresponding to rainfall events over a small catchment, and (4) the impact of scales of data and analysis on the hydrological modelling outcomes.