Abstract
Quantitative assessment of the impact of land use and climate change on hydrological processes is of great importance to water resources planning and management. The main objective of this study was to quantitatively assess the response of runoff to land use and climate change in the Zhengshui River Basin of Southern China, a heavily used agricultural basin. The Soil and Water Assessment Tool (SWAT) was used to simulate the river runoff for the Zhengshui River Basin. Specifically, a soil database was constructed based on field work and laboratory experiments as input data for the SWAT model. Following SWAT calibration, simulated results were compared with observed runoff data for the period 2006 to 2013. The Nash-Sutcliffe Efficiency Coefficient (NSE) and the correlation coefficient (R2) for the comparisons were greater than 0.80, indicating close agreement. The calibrated models were applied to simulate monthly runoff in 1990 and 2010 for four scenarios with different land use and climate conditions. Climate change played a dominant role affecting runoff of this basin, with climate change decreasing simulated runoff by −100.22% in 2010 compared to that of 1990, land use change increasing runoff in this basin by 0.20% and the combination of climate change and land use change decreasing runoff by 60.8m3/s. The decrease of forestland area and the corresponding increase of developed land and cultivated land area led to the small increase in runoff associated with land use change. The influence of precipitation on runoff was greater than temperature. The soil database used to model runoff with the SWAT model for the basin was constructed using a combination of field investigation and laboratory experiments, and simulations of runoff based on that new soil database more closely matched observations of runoff than simulations based on the generic Harmonized World Soil Database (HWSD). This study may provide an important reference to guide management decisions for this and similar watersheds.
Highlights
River runoff is an important fresh water resource that directly affects water resource utilization and maintenance
According to the runoff simulation results of two soil databases, we concluded that both databases provided satisfactory estimates after SWAT model calibration, but the local soil database constructed from field investigation and laboratory experiments produced better estimates
Our results showed that the combined effects were not the summation of the single effects, which explained why the total contribution rate of climate change and land use change to runoff reduction did not equal
Summary
River runoff is an important fresh water resource that directly affects water resource utilization and maintenance. 21st century, whereas surface runoff will decline in most subtropical arid regions and in Mediterranean regions [1]. In the past few decades, the runoff of most rivers in China has declined [2,3]. Changes in land use and climate are primary factors influencing changes in runoff [4,5,6]. Quantifying the impact of land use and climate changes on runoff provides essential guidance for developing new policies and taking management action. Land use change including deforestation, afforestation, and the development of agriculture and urban areas are common human activities that have important effects on hydrological processes [7,8]
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