Effects of land use/land cover and climate changes on surface runoff in a semi-humid and semi-arid transition zone in northwest China

Jing Yin,Fan He,Guo Yu Qiu,Yu Jiu Xiong

doi:10.5194/hess-21-183-2017

Abstract

Abstract. Water resources, which are considerably affected by land use/land cover (LULC) and climate changes, are a key limiting factor in highly vulnerable ecosystems in arid and semi-arid regions. The impacts of LULC and climate changes on water resources must be assessed in these areas. However, conflicting results regarding the effects of LULC and climate changes on runoff have been reported in relatively large basins, such as the Jinghe River basin (JRB), which is a typical catchment (> 45 000 km2) located in a semi-humid and arid transition zone on the central Loess Plateau, northwest China. In this study, we focused on quantifying both the combined and isolated impacts of LULC and climate changes on surface runoff. We hypothesized that under climatic warming and drying conditions, LULC changes, which are primarily caused by intensive human activities such as the Grain for Green Program, will considerably alter runoff in the JRB. The Soil and Water Assessment Tool (SWAT) was adopted to perform simulations. The simulated results indicated that although runoff increased very little between the 1970s and the 2000s due to the combined effects of LULC and climate changes, LULC and climate changes affected surface runoff differently in each decade, e.g., runoff increased with increased precipitation between the 1970s and the 1980s (precipitation contributed to 88 % of the runoff increase). Thereafter, runoff decreased and was increasingly influenced by LULC changes, which contributed to 44 % of the runoff changes between the 1980s and 1990s and 71 % of the runoff changes between the 1990s and 2000s. Our findings revealed that large-scale LULC under the Grain for Green Program has had an important effect on the hydrological cycle since the late 1990s. Additionally, the conflicting findings regarding the effects of LULC and climate changes on runoff in relatively large basins are likely caused by uncertainties in hydrological simulations.

Highlights

Both climate and land use/land cover (LULC) changes are key factors that can modify flow regimes and water availability (Oki and Kanae, 2006; Piao et al, 2007; Sherwood and Fu, 2014; R. Wang et al, 2014)
The objectives of this study were as follows: (1) to assess the surface runoff variability influenced by LULC and climate changes in recent decades in the Jinghe River basin (JRB) by using the Soil and Water Assessment Tool (SWAT) model, which differs from the climate elasticity model based on the Budyko framework; (2) to quantify the combined and isolated impacts of LULC change and climate variability on surface runoff in the basin from 1971 to 2005 by using scenario simulations after calibrating and validating the SWAT model at monthly and yearly timescales; (3) to discuss how LULC and climate changes affect surface runoff; and (4) to discuss the simulation uncertainty in the context of SWAT modeling due to parameterizations and Hydrol
The dryness index exhibited little change, a large dryness index (> 1.9) indicates that the climate became drier. These results indicate that the climate in the JRB changed dramatically over the last 4 decades, as characterized by decreased precipitation and increased temperature and dryness index values

Summary

Introduction

Both climate and land use/land cover (LULC) changes are key factors that can modify flow regimes and water availability (Oki and Kanae, 2006; Piao et al, 2007; Sherwood and Fu, 2014; R. Wang et al, 2014). Both climate and land use/land cover (LULC) changes are key factors that can modify flow regimes and water availability Since the 20th century, climate variability is believed to have led to changes in global precipitation patterns (IPCC, 2007), thereby changing the global water cycle and resulting in the temporal and spatial redistribution of water resources (Milly et al, 2005; Murray et al, 2012). J. Yin et al.: Effects of land use/land cover and climate changes arid and semi-arid regions characterized as vulnerable (Fu, 2003; Vorosmarty et al, 2010)

Objectives

Methods

Results

Discussion

Conclusion