Runoff formation from experimental plot, field, to small catchment scales in agricultural North Huaihe River Plain, China

S Han,D Xu,S Wang

doi:10.5194/hess-16-3115-2012

Abstract

Abstract. Runoff formation at an experimental plot (1600 m2), a field (0.06 km2), and a small catchment (1.36 km2) with a shallow groundwater table and a dense drainage system in the agricultural North Huaihe River Plain (China) was analysed based on the observed rainfall, runoff, and groundwater table data of 30 storm events that occurred during the 1997 to 2008 flood seasons. The surface runoff was collected and measured at the outlet of the furrow of the experimental plot, whereas the total runoff was collected and measured at the outlets of the drainage ditches of the field and the small catchment. The present study showed that the relatively narrow range of rainfall amounts resulted in significantly different runoff amounts at the 3 scales. When the groundwater is close to the surface, the runoff amount is a large percentage of the total rainfall. The difference in rainfall and runoff amounts was regressed against changes in the groundwater table, and a significant linear relationship was determined. Significant rainfall-runoff relationships were indicated for the events divided into 3 groups according to the initial groundwater table depths (as indicators of the antecedent moisture conditions): less than 0.5 m, more than 2.1 m, or between 0.5 m and 2.1 m. These findings suggest that saturation excess surface flow dominated the runoff response, particularly when the groundwater table was shallow. For almost all events, the groundwater table rose above the bottom of the drainage ditch. The total runoff amounts were larger both at the field and at the catchment than at the plot with only the surface runoff collected, which shows a considerable contribution of subsurface flow. Groundwater table depth, which indicates antecedent moisture conditions and influences lateral sub-surface flow to the drainage ditches, is an important parameter that influences runoff formation in catchments, including the study area with a shallow groundwater table and a dense drainage system.

Highlights

Over the past decades, numerous studies have been conducted to investigate runoff generation mechanisms
Surface 6ru2n2off occurrence is more frequent with crops at the Significant rainfall–runoff relationships were indicated for the events of the 3 groups with different initial groundwaseedling or early growth stage than later in the season
Based on our analysis of the observed rainfall and runoff data of 30 rainstorm events obtained from an experimental plot, a field, and a small catchment during the flood seasons from 1997 to 2008 at the North Huaihe Plain, the following conclusions are presented: 1. The relatively narrow range of rainfall amount resulted in significantly different runoff amounts from the experimental plot, field, and small catchment

Summary

Introduction

Numerous studies have been conducted to investigate runoff generation mechanisms. For rainfall-runoff studies in agricultural catchments, knowledge of the process originates mostly from the plot or the field (Burt and Slattery, 2006), and mechanisms of runoff generation are often detected or simulated at the catchment (Cerdan et al, 2002). Identification of runoff generation processes in an agricultural area requires further investigation at plot, field, and small catchment scales to characterise the dominant water flow pathways. Stream flows during storm runoff events were measured at 3 different scales: plot, field, and small catchment. The stream flows of the catchment and field were measured using a flow meter with water surface width, cross-sectional area, and average water depth data.

Runoff formation

Rainfall–runoff relationship with different initial groundwater table depths

Conclusions