Risk assessment of managed fracture-karst aquifer recharge with roof rainwater

Karst aquifer recharge with urban stormwater is an effective way, which can maintain natural water cycle, increase groundwater recharge, insure spring group spewing and urban flood control. But the fracture-karst aquifer has large permeability coefficient, fast water velocity and is hard to recover in short time once it is polluted; so the risk assessment of recharge project needs to be carried out. This paper took fracture-karst aquifer recharge project with roof rainwater in the west campus of University of Jinan as an example. To do so, the Australian Guidelines MAR was applied to the risk assessment, which mainly consisted of entry-level assessment, commissioning investigations, commissioning risk assessment and risk management. The entry-level assessment shows that this project has an overall low difficulty and certain feasibility. The monitoring of roof rainwater quality and groundwater quality before and after injection during commissioning investigations shows that except for the turbidity, roof rainwater treated by initial rainwater removal sedimentation and filtration basically meets the Ⅲ grade of quality standard for groundwater (GB/T 14848-93) and can quickly replenish the groundwater. The result of commissioning assessment indicates that the turbidity after the pre-treatment is still high and becomes the key hazard and critical control point. Therefore, risk management plan should be developed by improving pre-treatment device to decrease the turbidity. In addition, to ensure that the operation of this project can highly efficient and sustainable, the intensified finalperiod management is very important.