Effects of Reclaimed Water Use for Scenic Water on Groundwater Environment in a Multilayered Aquifer System beneath the Chaobai River, Beijing, China: Case Study

Reclaimed water has been widely utilized because of water shortages in Beijing, China. Approximately $18\mathrm{million}{\mathrm{m}}^3/\mathrm{year}$ of reclaimed water has been used for scenic water in the dry Chaobai River, and over $12\mathrm{million}{\mathrm{m}}^3/\mathrm{year}$ of such water has percolated from the river bed to recharge the underlying aquifers. Twenty-seven monitoring wells were built into 30, 50, and 80-m depths to quantify changes of groundwater level and quality in the multiaquifer system beneath the river and adjoining areas. The monitored data were utilized to develop a groundwater flow model and a numerical solute transport model to project future changes in the multiaquifer system. It was deduced from the monitored data that the hydrodynamic field in the 30-m depth aquifer was affected by reclaimed water recharge, whereas the 50 and 80-m depth aquifers were relatively slightly affected. The 80-m depth aquifer was the mainly exploited layer in the study area. Chloride ion was utilized to track the constituent movement of reclaimed water. The monitored data showed that groundwater quality in the 30 and 50-m depth aquifers was substantially influenced. Model prediction showed that groundwater level of 80-m depth aquifers over the next 20 years would decline by 22 m for water source A and B, and 12 m for water source C. At the same time, chloride concentration in three different aquifers would be substantially influenced by reclaimed water recharge, and the impacted area for these three aquifers was 22.2, 21.9, and $15.0{\mathrm{km}}^2$, respectively.