Study on the threshold of main factors restricting Jinan large karst springs spewing

Abstract

Jinan spring groups are famous large karst springs in north China.The interaction of natural factors and human impact had caused a decline in jinan karstic water level.Jinan spring groups began to appear cutoff in 1972,and the cutoff lasted from1972 to 2002.To protect the jinan springs,some measures,like reducing groundwater exploitation and artificial recharge have been carried out.The result of regression analysis shows that,during that cutoff period,the main reason affecting spring water level is groundwater exploitation,but since 2003,Jinan spring groups have resumed spewing,and groundwater exploitation is no longer a major factor affecting the spring water level.Based on the series dynamic observation data of Jinan springs water level from2004 to 2012,it is determined that the development degree of Jinan karst is relatively high by the method of dynamic characteristics curve types of karst water level.Through SPSS software,the influence degree on springs water level caused by precipitation and artificial recharge was analyzed.The regression—autoregressive model was built,which shows that the last month precipitation has significant effect on the water level.Using the higher order trend mathematical model about springs water level and precipitation,it is calculated that the monthly precipitation threshold is 26.65~30.73 mm to maintain Jinan spring dynamic stability in dry season.Finally,for spring protection,the paper puts forward that the artificial recharge water quantity is not less than 165 600 m3/d in dry season.Research suggests that springs water level is sensitive to climate change and human activities,and our research results can provide some scientific basis for the jinan springs protection and groundwater recharge.