| Jinan City is famous for its spectacular springs. They kept spewing naturally before the early 1960's. However, as karst groundwater provides a high-quality source for the industrial and household demands, groundwater has been intensively exploited in the city since 1980. Due to the continuous groundwater withdrawal, the conditions of recharge, flow and discharge of the groundwater have been greatly changed, and so has the original balance of the hydrochemistry. The springs are at risk of dry-out. Therefore, it becomes a chief and urgent task for the city to recover the springs and guarantee the water supply simultaneously, which is extremely important to the city's sustainable development.The dissertation presents the study on the changes in the recharge of the karst water system and its environmental effects under the present scenarios in the work area consisting of 4 discharge zones respectively in Ping'andian, Xijiao (west suburb), Shiqu (downtown) and Dongjiao (east suburb) within the spring catchment. The author analyzes the hydrochemistry of the karst water, the dedolomitization process of the carbonate aquifers, and the temperature effects and the altitude effects of stable isotopes of oxygen and hydrogen, by employing interdisciplinary methods involving hydrogeology, groundwater dynamics, hydro-geochemistry and isotope hydrology. Three tracer methods (including inert hydro-chemical compositions, predominant ion ratios and hydrogen and oxygen stable isotopes) were applied for the water samples, which were sampled in group in 2005 and 2006 respectively.There are three phases in the study. Firstly, the samples are screened by analyzing the precipitation input in the recharge zones based on the conservative and inert Cl- and NO3-. Except the samples from Xijiao, which indicate there was no apparent pollution, other samples are out. Then, the samples from Xijiao are studied for the water-rock interaction of the aquifers. The Mg2+/SO42- ratios during the dedolomitization process are obtained and the tracers show the characteristics of the hydro-geochemistry and pollution of the water. Finally, the recharge features of karst water are analyzed based on the temperature effects and altitude effects of deuterium and oxygen-18 in the precipitation. Conclusions can be drawn from the study integrated with three tracer methods as the following. Under the undisturbed conditions, the karst water recharges the upper phreatic aquifer or just discharges as springs. But after the groundwater has been exploited for a long term, the original flow pattern is totally changed and the local precipitation, surface water or unconfined groundwater infiltrate and mix with the karst water, which will make the karst water polluted in different degrees. Presently, the exploited water from Shiqu and Dongjiao is a mixture of local precipitation, local shallow groundwater and karst water. Most of the exploited water from Xijiao and Ping'andian is still karst water, only a small part being mixed with local precipitation.The dissertation proves a new and effective methodology to study the nature of karst groundwater. Variety of the water-bearing media in karst area defines the diversity of flow pattern of karst water. The integrated application of the three tracer methods makes up the weak points of an individual method. The results indicate that the exploited"karst water"in Jinan is no more the pure karst water in traditional conceptions, which can be a valuable reference when making a sound plan to recover the springs and satisfy the water demands from industries and homes at the same time.
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