Climate change may have substantial impacts on water cycling, affecting water resources. As predictions from climatic models and findings in some regional climate studies, climate change varies significantly by location. The response of water cycle is also expected to be varied among areas with different environmental conditions. This study is to investigate the potential differences in magnitude of hydrological responses to the changing climate among different climatic zones along the North-South Transect of Eastern China (NSTEC). NSTEC, the 15th transect of IGBP, covers seven climatic zones ranging from North Temperate Zone (NTemp, northern bound) to North Tropic Zone (NTrop, southern bound). Both air temperature (Ta) and annual precipitation (PPT) show increasing gradients along the transect.
A simplified water balance equation was used in the study, i.e., WY (water yield) = PPT – ET (evapotranspiration). ET was estimated using an empirical model, which is a function of land cover type, PET (potential ET) and PPT. Climate data was obtained from 300 meteorological stations within the transect region; land cover maps were based on Land sat derived classification. Areas of transformed land covers were removed from analysis to tease out the influence of land cover change.
Results/Conclusions
We found that Ta increased significantly during the period of 1980-2000, with the rates of change varied among the climatic zones (0.03-0.67 °C/yr). However, PPT did not show significant changes in any of the zones. Similarly, ET and WY did not show significant changes in any of the climatic zones during the same period. PPT was the dominant factor influencing the temporal dynamics of ET and WY; the effects of Ta, with the occurred increasing extents, were not notable. In the spatial dimension, ET increased from NTemp to NTrop, whereas, WY showed the same pattern as ET. The results also showed that PPT was slightly higher but WY was lower in forested area compared to non-forested area. Future distribution of water resources and their temporal changes will be greatly influenced by variation of PPT in the NSTEC region. Forests may be favored for increasing PPT, but it reduces WY due to higher ET compared to other land cover types. Forestation practice needs to consider the specific climatic conditions as well as tradeoffs between forest growth and water resources.
