Risk Assessment Of Fracture-karst Aquifer Recharge In Jinan Spring Area

Karst groundwater is a great resource for spring spewing in Jinan city, while the directrecharge area of groundwater was damaged by urbanization. Undoubtedly, aquifer recharge isan effective measure to promote sustainable development of local groundwater. Consideringthe facture-karst aquifer has a high hydraulic conductivity, risk assessment and managementare needed for aquifer recharge projects in Spring Area.Now, there are few studies on (karst) groundwater recharge at home and abroad. Healthrisk assessment model of U.S.EPA was widely applied in water quality, while the potentialhazards before and after projects’ construction were neglected. Australia has a rich experienceon risk assessment of MAR (managed aquifer recharge) and issued the Australian Guidelinesfor Water Recycling. The guidelines also contained a framework of managing health andenvironmental risk, which has used for hazards identification and management timely of mostMAR projects in Australia. Therefore, it is reliable to use Australian risk assessmentframework for karst groundwater recharge in Jinan.The framework of managing health and environmental risk was consisted of entry-levelassessment, pre-commissioning investigations, pre-commissioning risk assessment (maximal&residual risk) and risk management. Firstly, the viability and degree of difficulty wereassessed before construction. Subsequent management was also attached importance duringoperation. In this case, limestone aquifer recharge with roofwater pilot project in the westcampus of University of Jinan was evaluated by the framework. The project collected roofrunoff in flood seasons and injected it into carbonate aquifer with a tube well (250m) afterfirst-flush removal, precipitation and filtration, which has a obvious economic benefit withbenefit-cost ratio of4.52and annual total benefits of￥31,280,000.It is shown that this project has a low difficulty and a high feasibility. Monitoring ofroofwater and groundwater in recharge well was conducted during pre-commissioninginvestigations. Before recharge, treated roofwater quality basically met the III grade of qualitystandard for groundwater (GB/T14848-93). Furthermore, minor corrosion was occurred between rainwater and ambient aquifer media after recharge. Clogging may be produced by arelative high pH and turbidity of roofwater, which could be alleviated by calcite dissolution.The average flow velocity of groundwater with a depth of over180m in karst channel is9～20m/h, which has a high efficiency of groundwater recharge. Pre-commissioning riskassessment indicated that turbidity is the key hazard and critical control point. Consequently,risk management plan should be developed by improving pre-treatment device to decreaseturbidity. In addition, later running management, emergency control and publicity educationof water resources are also needed.