To investigate the evolution trend of water quality in Dongping Lake after South-North Water Transfer Project operation as well as to ensure the safe usage of the water receiving areas, water samples were collected and determined before and after water delivery in different hydrological seasons. Then, comprehensive pollution index method, comprehensive nutrition state index method and health risk assessment model were utilized to evaluate the quality, nutrition, and health risk of Dongping Lake water. Results showed that the quality of Dongping Lake water still met level Ⅲ (light pollution) no matter before or after water delivery. The nutrition state was improved from light eutropher before water delivery to mesotropher after water delivery. The health risk level was reduced from high-medium before water delivery to medium level after water delivery. In summary, the operation of the eastern route of South-North Water Transfer Project is beneficial for water environment improvement of Dongping Lake.

As nitrate pollution in groundwater has become increasingly serious in recent years, nitrogen isotope was adopted in this paper to define its sources in a typical agricultural area of Dong'e hydrogeological unit. The results show that: Higher content of NO₃^- detected in shallow groundwater is 27.77 mg/L on average and δ¹⁵N content ranges from 7.8‰ to 12 ‰, indicating that shallow groundwater is mainly contaminated by sewage or feces. In contrast, less NO₃^- in deep groundwater (karst water) has an average value of 12.81 mg/L and δ¹⁵N content is between 7.2‰ and 14.3‰, which is closely related to human disturbance as mentioned above. In addition, considering relatively low groundwater quality at some monitoring sites, reasonable fertilization is a better choice in the study area to reduce nitrate source in groundwater.