| Karst-water resource is an significant part of the groundwater resources. The exploitation of Karst-water is important for the sustainable development of the social-economic and the improvement of living standards. The water resources assessment and management depends mostly on the water regime study. Therefore, in order to reasonable use of groundwater or to prevent the disasters, the water regime study is a must.Taiyuan city is a city which is short for water supply. The Karst-groundwater in Lancun spring area is the primary water supply for Taiyuan city, also the strategic water supply when in the emergent stage. With the rapid growth of economy, the water demand grows dramatically in accordance. As a result, the confliction between water demand and water supply becomes more and more serious. What's more, the lacking knowledge about water management made the situation even worse. The abundant and lump pumping of groundwater has caused the regional great drawdown of groundwater and the dry up of springs within the spring area. The Karst-water system in Lancun spring area is now under serious crisis of being exhausted. How to protect the system from being dried up is pressing. At present, the "Wanjiazhai "project transfering Yellow river water to Shanxi Province is under its way. This project will release the current water crisis somewhat for Taiyuan city, and it provides a gold chance for the water protection in Lancun spring area. Therefore, the water regime study at this time of great mean in effectively controlling of the continuous drawdown situation for the Karst water system in Lancun spring area, and for the Karst-grounwater system protection ,also, it is of great mean in preventing the water quality from getting deterioration.This study first qualitatively analyzed the water regime. The result shows that:The multi-year regime shows obvious stages characteristic: The steady period, from the year of 1954 to 1969. The water level behaves relatively steady, with little ups and downs around 814.3 m height; The slowly drawdown period from 1970 to 1987, with little fluctuantly draw down. The average water draw down velocity in this period is 0.38m/a; The fast draw down period from 1988 to 2000, with an average draw down speed of 1.78m/a; The slowly draw down period from 2001 to 2003.The yearly water level also shows stages characteristic: Before 1976, the difference between the highest water level and the lowest level within a year is very small, even the biggest difference is littler than 0.5m, showing that the system is under balancing condition. From 1976 to 1986, the water level difference become larger and with small fluctuation, but still littler than 1m, showing that the system at this time is under dynamic balancing condition. After 1987, the water level difference changes violently, and what's more, the difference is all larger than lm, fluctuating around 2.2m, indicting that the Karst-water system is broken.The reason why the water regime shows such behavior is that, the precipitation is continues decreasing and the water exploitation is increasing gradually. When the income couldn't meet the output for a long time, the storage volume would be taken, which would surely result in the groundwater level draws down. It would take much longer time for the precipitation water infiltrating down into the Karst-water system, due to the wide rang and complex configuration of the studying Karst system, and this phenomenon is called time delay. The study result shows that, not only the current year's precipitation contributes to the water level changes but also the previous five year's.On the basis of this qualitatively analysis and considering the specific character of the studying area, timely and spatially unevenness of water baring and distribution, the complicated water flow condition and the limited hydro-geological parameter, choose the stochastic model to study the water regime using the long series of monitoring data. The stochastic water level model built using genetic algorithm method shows that: the precipitation is the number one influencing factor, and the artificial exploitation second, infiltration from watercourse of Fen river and the lateral discharge to the adjacent Xizhang pore groundwater basin also have some effect on the Karst-water level in Lancun spring area.The precipitation and the infiltration through Fen River watercourse were forecasted using the time serial method. After that, the water levels of the five schemes according to the water protection goal of Lancun spring area were forecasted, using the model built. The forecasting result shows that: for the first scheme, the Lieshihan spring is expected to revive in the year of 2030 under the basis of no exploitation of Karst-water. But since the Karst water is vital to the economic and domestic development of Taiyuan city, shut down all the pumping well is unpractical. So in the current situation, the revival of Lieshihan spring is still out of the question. If the exploitation remains the current situation, then, the water level will draw down fluctuantly, but the extent is small when compared to the previous draw down. If the water pumping will cut down to the permissible exploitation quantity, the water level will rise. But due to different hypotheses of lateral discharge to Xizhang pore water basin, the water level rising extent differs. The lateral discharge in the scheme four is smaller than the scheme three, so to the end of 2030, the water level forecasted by scheme four is 0.5m's higher than the scheme three. For the fifth scheme, if the Karst-water exploitation will cut down 40 million m~3/a under current pumping, then the water will rise to 793.15m till the end of 2030, with 10m water rise, which is the biggest of the five schemes. And this scheme is feasible after the "Wanjiazhai" water transfering project is finished. So this scheme is the best scheme.The water chemical composition of #10 in Lancun and the #14 in Zaogou, were analyzed. The result shows that: with the Karst-water level draws down, the calcium and bicarbonate draw down somewhat, hoever, the sulfate, sodium and chloride rise somewhat. The water type doesn't change during these years according to the result of Shukaliefu classification method. But the piper ternary chart reveals that: since 1985, the water quality is deteriorating, trending to strong acid type, and the sodium and potassium composition present rising trend.At last, the water quality of #10 in Lancun and #14 in Zaogou was evaluated from the aspect of drinking safety using Nemero index method. The result shows that: the water quality is choiceness or all right through these years, but the Nemero index has the trend of growing, that means, the water quality is becoming worse.
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