KARST HYDROLOGY AND CHEMICAL CONTAMINATION

Ground-water flow in karst aquifers is very different from flow in gra nular or fractured aquifers. Karst ground-water flow is often turbulen t within discrete conduits that are convergent in their upper reaches and may be divergent in their very lower reaches, simulating the flow pattern of surface water streams that are dendritic or trellised but w ith discharge to one or more springs. Significant precipitation events tend to flood karst aquifers quickly, causing a rapid rise in the pot entiometric surface that may flood older, higher levels which discharg e to a different set of springs. The epikarstic zone in karst terranes stores and directs infiltrating water down discrete percolation point s. Chemical contamination may be fed directly to a karst aquifer via o verland flow to a sinkhole with little or no attenuation and may conta minate down-gradient wells, springs, and sinkholes within a few hours or a few days. Contaminants may also become temporarily stored in the epikarstic zone for eventual release to the aquifer. Flood pulses may flush the contaminants to cause transiently higher levels of contamina tion in the aquifer and discharge points. The convergent nature of flo w in karst aquifers may result in contaminants becoming concentrated i n conduits. Once contaminants have reached the subsurface conduits, th ey are likely to be rapidly transported to spring outlets. Traditional aquifer remediation techniques for contaminated aquifers are less app licable to karst aquifers.