The South-to-North Water Transfer (SNWT) Project of China is the largest of its kind ever implemented. Its Middle Route, completed in 2014, will transfer 14 billion m3 of water annually from the upper Han River, a tributary of the Yangtze and the water supplying area, to North China Plain by 2030. Thus, water quality in the 95,000 km2 upper Han River basin is of great concern for the interbasin water transfer project. A watershed management initiative has been implemented in the basin since 2004, and the ultimate objectives are to quantify basin’s ecosystem functioning and to develop an integrated management system with respect to water resources conservation. The program includes several themes such as land use and land cover change, biogeochemistry of carbon and nutrients, and biomonitoring of the aquatic environment, and finally development of a watershed management system for water conservation. For the past 10 years, we have been systematically monitoring changes in land use and land cover through satellite imageries, using stable isotope technique to identify carbon and nitrogen sources in the river ecosystem, and implying diatom community as bioindicator for the aquatic health assessment, and consequently conducting ecological restoration for water quality conservation.
Results/Conclusions
The results showed that conservation projects such as‘Grain-for-Green’ Program (GGP) had effectively protected the existing forests, facilitated vegetation recovery from 34.8% to 72.6%, and croplands decreased from 31.5% to 8.1% over a 30-year time period. The sources of POM primarily included soil organic matters and planktons with the C isotope range of -28.83‰~ -22.04‰. There were larger POM in spring (0.40 ~39.80 mg/L) and winter (0.06 ~41.76 mg/L). The sources of dissolved nitrate originated from precipitation, plankton and fertilizes with the isotope range of amminion and nitrogen of -1.48 ~ 15.86‰, -5.86 ~ 17.20‰, respectively. The δ15N of sediment and nitrate of river in residential and cultivated zones were larger than that in forest zone, implying the river was interfered by human activities (e.g., agriculture). We also derived spatio-temporal patterns of benthic diatoms and developed a benthic diatom-based index of biotic integrity (BD-IBI) for the aquatic environment assessment. We explored the determinants driving the benthic metabolism under the influence of environmental variables including water quality, riparian canopy cover and upstream catchment land cover. This programmer provides the justifications of the watershed management initiative and the results are comprehended with respect to the water conservation in the Han River basin.