Abstract
Assessing the impacts of land use and cover (LUCC) change and climate change on discharge and sediment load is beneficial for the regional management of water resources and the water environment. The Mann-Kendall test and soil and water assessment tool (SWAT) model were applied to analyze the change trends of meteorological and hydrological variables and to quantitatively assess the response of discharge and sediment load to LUCC and climate change, respectively, in the Hunhe River Basin (HRB). The results showed that LUCC changed little during 1980–2009, mainly from forestland (−0.36%) to other land use types, such as urban land (+0.13%) and grassland (+0.13%). Temperature increased significantly (p < 0.01), and precipitation showed a non-significant decreasing trend. Discharge showed a non-significant decreasing trend, and sediment load significantly (p < 0.05) decreased. The Nash–Sutcliffe efficiency (NSE), coefficient of determination (R2), and percent bias (PBIAS) during the calibration and validation periods indicated that good performance was achieved for the discharge simulation (NSE: 0.77–0.79; R2: 0.79–0.84; PBIAS: −9.61–1.48%) and satisfactory performance for the sediment load simulation (NSE: 0.65–0.77; R2: 0.65–0.78; PBIAS: −2.56–8.31%). The calibrated SWAT model was successfully utilized to assess the impacts of LUCC and climate change on discharge and sediment load, finding that the combined impact of LUCC and climate change decreased the annual discharge and sediment load by 22.65% and 31.51%, respectively. Minor changes in annual discharge (+0.08%) and sediment load (−1.33%) were caused by LUCC, and climate change led to a pronounced decrease in annual discharge (−22.69%) and sediment load (−30.61%). These findings indicate that climate change rather than LUCC dominated the hydrological alterations in the HRB. This study provides important information for decision makers to identify the reasons for changes in hydrological alterations and to design adaptive measures.
Highlights
Analyzing the change trends of land use and cover change (LUCC) and hydrometeorological variables and assessing the impacts of LUCC change and climate change on discharge and sediment load are crucial for the regional management of water resources and the water environment
The upstream Hunhe River is mountainous with elevations ranging from 400 to 800 m a.s.l., and the downstream area is dominated by hills with elevations of 100–200 m a.s.l
On the basis of the criteria of Moriasi et al [36], we found that good model performance was achieved for discharge, and the sediment load simulation performance was satisfactory
Summary
As an important aspect of environmental change, LUCC is primarily caused by human activities. LUCC changes the hydrological conditions of a watershed, such as flood frequency and severity, base flow, discharge, and soil erosion [7–9]. As another important aspect, climate change alters changes in precipitation and temperature, which in turn affects the hydrological cycle [10], and changes the flow routing time, peak flow, flow volume, and sediment yield [9,11,12]. Previous studies show that global land change exhibits deforestation and agricultural expansion in tropical region and reforestation/afforestation, cropland intensification and urbanization in temperate region [13], and the increasing global temperature and the change of precipitation patterns have greatly affected regional water resource sustainability [10,14,15]. Analyzing the change trends of LUCC and hydrometeorological variables and assessing the impacts of LUCC change and climate change on discharge and sediment load are crucial for the regional management of water resources and the water environment
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