Abstract
The present study predicts and assesses the individual, combined, and synergistic effect of land-use change and climate change on streamflow, sediment, and total phosphorus (TP) loads under the present and future scenarios by using the Soil and Water Assessment Tool (SWAT). To predict the impacts of climate and land-use change on streamflow, sediment, and TP loads, there are 46 scenarios composed of historical climate, baseline period climate, eight climate models of Coupled Model Intercomparison Project phase 5 (CMIP5) of two representative emission pathways (RCP4.5 and RCP8.5), after downscaled and bias-corrected, two observed land-use maps (LULC 1995, LULC 2015) and the projected two future land-use maps (LU2055 and LU 2075) with the help of CA-Markov model to be fed into SWAT. The central tendency of streamflow, sediment, and TP loads under future scenarios is represented using the annual average. The intra-/inter-annual variation of streamflow, sediment, and TP loads simulated by SWAT is also analyzed using the coefficient of variation. The results show that future land-use change has a negligible impact on annual streamflow, sediment, TP loads, and intra-annual and inter-annual variation. Climate change is likely to amplify the annual streamflow and sediment and reduce the annual TP loads, which is also expected to reduce its inter-/intra-annual variation of TP loads compared with the baseline period (2000–2019). The combined impact of land-use and climate change on streamflow, sediment, and TP loads is greater than the sum of individual impacts for climate change and land-use change, especially for TP loads. Moreover, the synergistic impact caused by the interaction of climate and land use varies with variables and is more significant for TP loads. Thus, it is necessary to consider the combined climate and land-use change scenarios in future climate change studies due to the non-negligible synergistic impact, especially for TP loads. This research rare integrates the individual/combined/synergistic impact of land-use and climate change on streamflow, sediment, and TP loads and will help to understand the interaction between climate and land-use and take effective climate change mitigation policy and land-use management policy to mitigate the non-point source pollution in the future.
Highlights
Climate and land-use change critically impact water resources by directly affecting the hydrologic processes (Ervinia et al, 2019; McDonough et al, 2020)
This study explores and predicts the individual and combined impact of land-use change and climate change on streamflow, sediment, and total phosphorus (TP) loads in the future by systematically aggregating two representative emission pathways (RCP4.5 and RCP8.5), eight GCMs, three 20-years temporal blocks, three land-use maps (LULC 2015, LULC 2055, and LULC 2075)
This study compares the individual impact of past land-use map (LULC 1995) and climate (1980–1999) on streamflow, sediment, and TP loads at the 20-years temporal block with the baseline period
Summary
Climate and land-use change critically impact water resources by directly affecting the hydrologic processes (Ervinia et al, 2019; McDonough et al, 2020). Previous studies have shown that climate and land-use change exert considerable impact on the water quantity and quality (El-Khoury et al, 2015; Lintern et al, 2018). Both climate and land use can modulate the nutrient turnover and greenhouse gas emissions due to the interplay of climate and land use (Peters et al, 2019). It is necessary to simultaneously consider climate and land use in future studies of variation in hydrology and non-point source pollution
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