Isolating the impacts of climate change and land use change on decadal streamflow variation: Assessing three complementary approaches

Assessing the respective impacts of land use change and climate change on decadal streamflow variation is important for water resources management. By using: (i) a simple eco-hydrological approach, (ii) an elasticity differential analysis, and (iii) a calibrated physically-based MIKESHE model, we have qualitatively and quantitatively isolated the relative contributions that land use change and climate change made to decadal streamflow changes in Chaohe watershed (4854 km2) located in northern China. This is an important watershed of Miyun Reservoir that supplies 70% of drinking water for Greater Beijing Area (Population over 19 M). The results suggested that streamflow of the watershed, compared with the reference period from 1963-1979, greatly decreased during 1980–1989 and 2000–2008, whilst it slightly changed during 1990–1999. The insignificant streamflow change for 1990–1999 was due to the effects of less soil water storage capacity on hydrological impact of land use change. However, the change impacts (i.e., land use change impacts dQ_Landuse and climate change impacts dQ_Climate) for 1980–1989 and 2000–2008 seem different between the approaches: dQ_Climate were almost similar to dQ_Landuse for these two periods according to eco-hydrological approach, whilst dQ_Climate from the differential elasticity-based analysis only 33% and 45% and from MIKESHE modeling 51% and 78% for 1980–1989 and 2000–2008, respectively. We found that the different results were mainly caused by errors associated with each approach. By taking into account the errors of each approach, a general consistent results could be arrived from the three approaches, i.e., streamflow reduction of 1980–1989 and 2000–2008 was accounted for by land use change and climate change with almost similar magnitude contribution. We emphasized that various source of errors and uncertainties may occurre in the different approaches. This required a careful interpretation of the results on isolating hydrological impacts of land use change and climate change. As hydrological impacts of land use change and climate change may be temporally varied, it is requisite to manage water resources adaptively to address future climate change and water resources shortage.