Variations in evapotranspiration (ET) and gross primary production (GPP) due to climatic fluctuations deserve specific considerations for sustainable water and agricultural management. A Vegetation Interface Processes (VIP) model assimilated with Terra-MODIS remotely sensed leaf area index was used to simulate their spatial and temporal patterns from 2000 to 2010 in the Songhua River Basin of Northeast China at 1-km grid and 1-h time step. The predicted ET and GPP were well verified with the eddy covariance measurements, and the ET was in agreement with that derived from water balance. Over the whole basin, average annual precipitation (P), ET, GPP and water use efficiency are 458 mm, 374 mm, 1067 gC m−2 and 2.86 gC m−2 mm−1, respectively. Both ET and GPP display significantly spatial variability, with ET presenting different and good relationships with precipitation for different kinds of land use covers (LUCs); and GPP a unified good relationship across almost all the LUCs except water body. Over the years from 2000 to 2010, Normalized Difference Vegetation Index (NDVI), especially crop NDVI, experienced a trend of increasing. GPP showed no significant trend. ET showed an increasing trend for cropland and grassland, a decreasing trend in water body and wetland, no significant trend for other vegetation types and a weakly increasing trend for the whole basin. Annually, ET roughly follows precipitation, whereas GPP was mainly regulated by radiation (Rn). The inter-annual variability for the eco-hydrological elements with the order of the coefficient of variation (CV) being P (0.13) > EC (0.055) > ET (0.05) > Rn (0.037) > GPP (0.019) > NDVI (0.01) is less than their spatial variability with the order of CV being EC (0.23) > P (0.22) > GPP (0.19) > ET (0.15) > Rn (0.05). The highest spatial variability of ET and GPP in grassland implies the incurring problem of degradation in western basin. The low spatial variability in paddy relates agricultural management.
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