Sensitivity of terrestrial water and carbon fluxes to climate variability in semi-humid basins of Haihe River, China

Inter-annual climate variability dominates the evolution of eco-hydrological processes over the water limited basins. Haihe Basin in semi-humid northern China is under significant climate change and serious human disturbance during the recent decades. Integrated with NASA Terra-Modis remote sensing LAI data products, the VIP eco-hydrological model is used to predict the spatiotemporal variations of evapotranspiration (ET) and vegetation gross primary production (GPP) over two catchments of Haihe River branches from 2000 to 2013. Along with precipitation increasing, average annual ET and GPP are significantly increasing. The trends are more distinct over the mountainous upstream areas. The inter-annual variations of ET and GPP are highly correlated with the 12-month SPI (Standardized Precipitation Index), while the monthly GPP is related clearly with 3-month SPI. Sensitivity analysis shows that there are remarkable differences in the elasticity coefficients of both ET and GPP to the climatic factors. It is found that precipitation, solar radiation and leaf area index are the most sensitive factors to ET and GPP in the study basin. The results are helpful to understand the catchment eco-hydrological mechanisms and their responses to climate change.