The construction of the flow duration curve and the characteristics of parameters in Northern Shaanxi of China

Abstract: Predicting daily runoff time series in ungauged catchments is both important and challenging. Flow duration curve is an important characteristic of daily runoff of a river, and important for the design of water conservancy projects. Therefore, in the ungauged catchments, the evaluation of distribution functions and the parameters of flow duration curve is a helpful method to understand the characteristics of the flow duration curves. This study uses data collected at 19 hydrological stations to evaluate the applicability of 11 distribution functions to simulate flow duration curves in Northern Shaanxi of China. Among the selected distribution functions, the log normal model is the most suitable model to develop flow duration curves in Northern Shaanxi. By using a multivariate linear regression model, a regional model that are functions of watershed geomorphologic and climatic characteristics based on distribution parameters is constructed. Moreover, Analysis of Baijiachuan hydrological station, found that parameters a, b showed a decreasing trend over the studied period. This study presents an innovative approach to evaluate runoff based on flow duration curves that consider the impacts of geomorphologic and climatic characteristics, which can be used to provide guidance for construction and planning of soil and water conservancy projects in areas without measured flow data, especially in Northern Shaanxi of China.

Keywords: Flow duration curve; Distribution function; Log normal model; Geomorphology; Climate