Functional Regionalization And Renewable Capacity Of Karst Water System In The Semi-humid Area,Central Southern Shandong Province

How to rationally develop,utilize and protect karst water resources has become an important problem to be solved in the social and economic development of the semi-humid area in central southern Shandong Province.In this study,we select Pingyi-Feixian area in the semi-humid area,central southern Shandong Province,as the research area,where a large number of field investigations,experiments and comprehensive research have been carried out.We focus on the composition of karst water system,the characteristics of hydrodynamic field and the karst water system structure,runoff and discharge conditions,and so on.We also identified the conceptual model,formation age and renewable ability of karst water system.The main understanding and innovative conclusions have been achieved as follows:?1?The karst water system has special hydrogeological characteristics of“two sources and multiple sinks,multi-layer storage and multiple fault-dominated”in the hard structure.it also being distinctive formation mechanism and influence factors of renewable capacity,at different depth of karst water system.?2?There were composed of four subsystems,with the deterministic functional regionalization,which include two direct recharge zones,one indirect recharge zone and three discharge zones in the karst water system.In the direct recharge zones,the intense water-rock interaction and strong karst erosion have been in progress,because of the abundant recharge and the strong permeability.In the discharge zones,karst fissures have been well developed with strong water abundance,and undeveloped with water-rock interaction,generally the specific capacity has been greater than 5,000m³/d.?3?There has been obvious difference in characteristics of formation age and renewable capacity in the different subsystems,even in recharge zones or discharge zone.where as being no correlation with the stratigraphic age of the aquifer.The karst water retention time has been 3¹7 years in the direct recharge zones,and been 14²5 years in the discharge zones.The forming age of karst water has between 146³808 years in the direct recharge zones,where the younger its formation age in the shallower aquifer,and the forming age of karst water has been 1046⁵403 years in the discharge zones,where the older karst water has been farther away from the recharge area and longer runoff path.?4?There has been distinct sampling segment by the value of ¹⁴C content of karst water,and the distribution of samples has an inherent spatial correlation with the functional regionalization.In the discharge zones,there bas been a negative correlation between the value of ¹⁴C content and the value of main anions and anions content in karst water.In the direct recharge zones,there generally bas been no correlation between the value of ¹⁴C content and the value of the main cation and anion content,except for Ca²⁺and Mg²⁺,because of the complex recharge and strong hydrodynamic erosion.?5?It has been found that the main factors,mechanism and influence mode of the renewable capacity in the study area,which beyond the functional regionalization and the aquifer distribution,have been controlled by the length of karst water runoff path,burial depth,karst erosion and connectivity,as well as the surface water accumulation and recharge abundance of karst water.In the direct recharge zones,atmospheric precipitation infiltration recharge may be remarkably increase because of the more dense surface vegetation.In the discharge zones,massive artificial pumping of karst water may stimulate the renewable capacity of karst water system and increase the amount of karst water resources.?6?There have been three focus on the rational development and effective protection of karst water resources,such as the control of the pumping mode,the control of the pumping area and the control of the exploitation intensity.In the direct recharge zones,it is necessary to enhance the ecological coverage of trees and shrubs,such as pine,cypress,locust and thorns,improving the conservation and protection ability of karst water resources.In the discharge zones,it is necessary to enhance the ability of multi-class water and soil conservation.