Identifying separate impacts of climate and land use/cover change on hydrological processes in upper stream of Heihe River, Northwest China

Abstract

Climate change and land use/cover change (LUCC) are two factors that produce major impacts on hydrological processes. Understanding and quantifying their respective influence is of great importance for water resources management and socioeconomic activities as well as policy and planning for sustainable development. In this study, the Soil and Water Assessment Tool (SWAT) was calibrated and validated in upper stream of the Heihe River in Northwest China. The reliability of the SWAT model was corroborated in terms of the Nash–Sutcliffe efficiency (NSE), the correlation coefficient (R), and the relative bias error (BIAS). The findings proposed a new method employing statistical separation procedures using a physically based modeling system for identifying the individual impacts of climate change and LUCC on hydrology processes, in particular on the aspects of runoff and evapotranspiration (ET). The results confirmed that SWAT was a powerful and accurate model for diagnosis of a key challenge facing the Heihe River Basin. The model assessment metrics, NSE, R, and BIAS, in the data were 0.91%, 0.95%, and 1.14%, respectively, for the calibration period and 0.90%, 0.96%, and −0.15%, respectively, for the validation period. An assessment of climate change possibility showed that precipitation, runoff, and air temperature exhibited upward trends with a rate of 15.7 mm, 6.1 mm, and 0.38 °C per decade for the 1980 to 2010 period, respectively. Evaluation of LUCC showed that the changes in growth of vegetation, including forestland, grassland, and the shrub area have increased gradually while the barren area has decreased. The integrated effects of LUCC and climate change increased runoff and ET values by 3.2% and 6.6% of the total runoff and ET, respectively. Climate change outweighed the impact of LUCC, thus showing respective increases in runoff and ET of about 107.3% and 81.2% of the total changes. The LUCC influence appeared to be modest by comparison and showed about −7.3% and 18.8% changes relative to the totals, respectively. The increase in runoff caused by climate change factors is more than the offsetting decreases resulting from LUCC. The outcomes of this study show that the climate factors accounted for the notable effects more significantly than LUCC on hydrological processes in the upper stream of the Heihe River.

Long Term Quantification of Climate and Land Cover Change Impacts on Streamflow in an Alpine River Catchment, Northwestern China

“…We concluded that the climate change and land cover change both contributed to the increase of the streamflow, whereas climate change was the main factor, consistent with the conclusions of several previous studies [17,36,53]. Because of the changes to climate and land cover, the rainfall-runoff relationship has varied, which has also been demonstrated in previous studies [1,31].…”

“…Overall the streamflow increasing due to climate change by 14.08% of total streamflow over the last 50 years, in agreement with the results of Wu et al [53] and Zhang et al [17]. The latest study also confirmed that the climate dominate the streamflow effects more significantly in the upper stream of the Heihe River rather than land cover change [36]. Figure 10 shows decadal changes of monthly precipitation, average temperature, and streamflow compared to values from the 1960s.…”

“…However, there has been little work done to assess the impact of the changing environment on streamflow of the upper mountainous watershed over a long time period. Yang et al [36] have identified the separate impacts of climate and land cover changes on hydrological processes in upper stream of HRB based on the obtained climate data and land use/cover change data from 1981 to 2010. However, their study only focused on conditions over 30 years; long-term study on the climate and land cover change impacts still remains to be addressed.…”

Separation of the Climatic and Land Cover Impacts on the Flow Regime Changes in Two Watersheds of Northeastern Tibetan Plateau

“…where Δ represents the total change of a given hydrological element; hydrological elements can serve as statistic mean values over annual, seasonal, or monthly time scales [21].…”

“…Separation of the individual influence of the two factors on hydrological processes thus warrants the need for inputting the applicable status of two factors from the baseline period to the entire period. Yang et al [21] recommended that a combined statistical and modeling method could be used to resolve this bias and further identified the climate and land cover change impacts on the hydrological processes in the Heihe River. In that study, the results were more reasonable and offered greater accuracy than the traditional OFAT and other statistical methods.…”