Assessment of water quality risk from karst aquifer recharge with multi-source water in the Yufuhe river, Ji’nan

Ji’nan is well known for Spring City, while facing huge challenges of spring protection and security of water supply. The aquifer recharge with multi-source water is one of the effective measures to solve these problems. However, the quality of source water is still poorer than karst water, which would caused some risk of health and safety. Comparing the standard of groundwater quality and the background value of karst water quality, this work chose the risk monitoring indicators that exceed the standard in surface water sources or are inferior to background values. And adopting the Australian Guidelines of MAR, we assessed the water quality risk of the aquifer recharge with multi-source water in the Yufuhe river. In 2015, monitoring and index analysis were performed to the water quality of source water, pore well water and karst deep well water when Yellow River water and Wohushan reservoir water recharging the aquifers many times. The results show during the Yellow River water recharging, respectively in source water, pore water and karst water, the standard indexes of average turbidity are 1.4, 1.7 and 0.93, the standard indexes of sulfate’s average content are 0.93, 0.9 and 0.73 and although the content of chloride ion does not exceed the groundwater class III standard, it in the source water content is more than 2 times the groundwater content; during the Wohushan reservoir water recharging, respectively in source water, pore water and karst water, the standard indexes of average turbidity are 2.4, 1.1 and 0.43, the standard indexes of sulfate’s average content are 0.75, 0.84 and 0.66 and the standard indexes of ammonia nitrogen’s average content are 1.14, 1.47 and 1.35. We draw conclusion that the turbidity, sulfate and the movement of pollutants in the aquifers are at critical points for the whole Yufuhe aquifer recharge project. In addition, the risk of salinity should receive attention when the Yellow River water is used as the recharge source. Similarly, the risk of nutrient is also a concerned issue when the Wohushan reservoir water is the recharge source. Based on the above analyses, this paper offers some suggestions, such as limiting the proportion of karst water resources.