Abstract: Jinan, a city well known for its numerous springs, is now faced with spring dry out caused by human activities. In past years, the city has taken measures to protect the famous springs by limiting extraction from selfsupply wells, prohibiting extraction of centralized water supply sources, artificial recharging, etc., with no apparent success. In this paper, the mixing ratios of different recharging water sources were studies through spring level observation, tracer experiment, water quality test and analysis of karst development, complemented by mathematical modeling. The characteristics of changes of the spring level dynamics and electrical conductivity revealed that the source of recharge changes according to the season. Specifically, the springs were recharged mainly by the pipe flow from the southeast in wet seasons, and by the fissure flow from the southwest in dry seasons. The results show: in the discharging area of the karst water system, distinct correlation exists between the groundwater level and spring level dynamics; the groundwater level in Ordovician limestone correlates better with spring level than the karst water level in limestone of the Cambrian Zhangxia Formation; and artificial recharge in the Zhangxia Formation can not halt the declining trend in spring level. Based on 42 sets of data, our calculation shows that the contents of conventional ions in springs, such as Ca2+, Mg2+, Cl- and SO2-4, and total water hardness, lied between that of the karst waters of the Cambrian Zhangxia Formation and Ordovician. Moreover, in the flow of the four large spring groups, 11%32% came from the recharge of the Zhangxia Formation, 24%60% from the recharge of the Fengshan Formation and Ordovician, 5%10% from the Liyang Lake, 06% from the Xingji River, and 1%8% from the Yufu River. Artificial recharge in urban areas, therefore, would significantly influence the FiveDragon Pool. In conclusion, the northern karst developed heterogeneously; pipe flow coexisted with fissure flow as indicated by changes of spring level dynamics; and artificial recharge should be located in areas where Ordovician limestones are distributed.

Key words:  pipe flow, fissure flow, mixing ratio, recharge source, spring protection