T71 Rivers in Karst: Processes and Applications

Monday, 28 October 2002
8:00 AM - 12:00 PM

KARST IS A WORK IN PROGRESS WITH FEEDBACK MECHANISMS AND EXTERNAL FACTORS CONTINUALLY CHANGING THE ENDPOINT

Paper number: T71-4
Program: Technical Sessions
Time: 9:45 AM – 10:00 AM

Authors

Abstract

Karst aquifers and rivers develop in response to feedback mechanisms between the rock and groundwater flow, coupled with the imprint of the environment of formation, tectonic stresses, external factors, etc. Development of karst includes abandonment, redirection, and consolidation of water flowpaths at nonuniform rates over time. A familiar sequence example follows. Start with a recharge and/or base level change causing a steeper flow gradient which increases the likelihood that water chemistry is out of equilibrium with the karst rock, leading to solution which changes the hydrogeologic values, which may further change the gradient and result in consolidation of water flowpaths. The underlying principle is that karst reflects an ongoing evolution toward an effective drainage network for recharge water coupled with feedback mechanisms that modify the design requirements for optimal drainage. Recreating the history of development requires the determination of groundwater flow patterns over time.

External factors play a major role in changing design requirements for optimal drainage of recharge. These include climatic change, base-level change, presence of low K layers, breaching of low K layers, change of base level, soil development as it affects recharge water chemistry, etc. The karst we are attempting to model, may have hydrogeologic properties developed primarily during the last glacial period, that are currently being modified. Groundwater flow patterns reflect all of the above factors with feedbacks such as concentration of groundwater flow on the outside meander bends of karst rivers and the breaching of low K layers. Karst reflects a smorgasbord of impacting factors over its history of development, cybernetic feedback processes, and likely has not reached equilibrium with the present day environment or any environment in its history. Karst is a work in progress.