Impacts of Climate and Land-Use Change on Blue and Green Water: A Case Study of the Upper Ganjiang River Basin, China

Yongfen Zhang,Xiaofei Nie,Anguo Tu,Taihui Zheng,Aizhong Ye,Hua Zhu,Shiqiang Zhang,Chongjun Tang

doi:10.3390/w12102661

Abstract

Quantitatively figuring out the effects of climate and land-use change on water resources and their components is essential for water resource management. This study investigates the effects of climate and land-use change on blue and green water and their components in the upper Ganjiang River basin from the 1980s to the 2010s by comparing the simulated changes in blue and green water resources by using a Soil and Water Assessment Tool (SWAT) model forced by five climate and land-use scenarios. The results suggest that the blue water flow (BWF) decreased by 86.03 mm year−1, while green water flow (GWF) and green water storage (GWS) increased by 8.61 mm year−1 and 12.51 mm year−1, respectively. The spatial distribution of blue and green water was impacted by climate, wind direction, topography, and elevation. Climate change was the main factor affecting blue and green water resources in the basin; land-use change had strong effects only locally. Precipitation changes significantly amplified the BWF changes. The proportion of surface runoff in BWF was positively correlated with precipitation changes; lateral flow showed the opposite tendency. Higher temperatures resulted in increased GWF and decreased BWF, both of which were most sensitive to temperature increases up to 1 °C. All agricultural land and forestland conversion scenarios resulted in decreased BWF and increased GWF in the watershed. GWS was less affected by climate and land-use change than GWF and BWF, and the trends in GWS were not significant. The study provides a reference for blue and green water resource management in humid areas.

Highlights

In recent years, regional water cycle processes and the impacts on these processes from climate change have become topics of great academic interest [1,2]
The Nash–Sutcliffe coefficient (NS) values for all hydrological stations in each scenario for both the rate period and the validation period were above 0.6, indicating a “good” to “excellent” simulation (Table 2). The results of these statistical analyses indicate that the Soil and Water Assessment Tool (SWAT) model is applicable for the simulation of hydrological processes in the upper Ganjiang River basin and that this model can be used in further research (Figure 3)
The effects of climate and land-use change on blue water flow (BWF), green water flow (GWF), and green water storage (GWS) and their components were quantitatively analyzed with the SWAT model for different scenarios in the upper reaches of the Ganjiang River basin, which is a humid region in southeastern China

Summary

Introduction

Regional water cycle processes and the impacts on these processes from climate change have become topics of great academic interest [1,2]. Climate change can alter regional precipitation, temperature and evapotranspiration conditions, which affects runoff and exacerbates water scarcities [3]. As populations continue to grow, high-intensity human activities will alter land cover patterns, resulting in changes in water infiltration, evapotranspiration, and soil moisture conditions [4,5]. The concepts of blue and green water have provided new perspectives on water management in recent years [7,8,9,10,11,12,13]. These concepts were first introduced by Falkenmark [14]. Green water is a large part of global water resources

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Conclusion