Impact of reclaimed water in the watercourse of Huai River on groundwater from Chaobai River basin, Northern China

Reclaimed water is efficient for replenishing the dry rivers in northern China, but regional groundwater may be at risk from pollution. Therefore, samples of reclaimed water, river water, and groundwater were collected at the Huai River in the Chaobai River basin in 2010. The water chemistry and isotopic compositions of the samples were analyzed in the laboratory. The reclaimed water had stable compositions of water chemistry and isotopes, and the Na. Ca-HCO3. C1 water type. The water chemistry of the river water was consistent with that of the reclaimed water. A June peak of total nitrogen was the prominent characteristic in the shallow groundwater, which also had the Na. Ca-HCO3. C1 water type. However, the water chemistry and isotopes in most of the deep groundwater remained stable, and the water type was Ca-Mg-HCO3. The amount of reclaimed water recharging the groundwater was about 2.5 - 107 m^3/yr. All of the shallow groundwater was impacted by the reclaimed water, with the mixing proportion of reclaimed water ranging from 42% to 80 % in the dry season and from 20% to 86% in the wet season. Only one deep well, with proportions of 67% （dry season） and 28% （wet season）, was impacted. TDS, EC, and major ions （Na, K, C1, NHn-N, NO2-N, and NO3-N） were increased in the impacted wells.