The role of seasonal variation of precipitation/recharge for different climates in karst genesis behaviors

Abstract

Recharge is an important factor controlling dissolution processes during speleogenesis of karst aquifers. In former studies simplified assumptions were considered, where a maximum recharge rate is assumed while its fluctuation is ignored. Under the latter assumption, the karst genesis is clearly divided into two successive processes characterized by either a hydraulic head limitation (hydraulic control) or a flow rate limitation (catchment control). In this study, we consider a karst system evolving according to a maximum recharge rate linked to the seasonal variation of precipitation, which may lead to speleogenesis processes under hydraulic control or catchment control from the beginning of the karst genesis. We found that, without considering the recharge fluctuation, the enlargement of fractures as well as the dimensions of dissolving area under a long-term evolution tends to be underestimated. Moreover, in the cases of a large catchment area, the time required to reach the final dissolution patterns tends to be underestimated (i.e., earlier breakthrough), while it tends to be overestimated in the cases of a small catchment area. In addition, the flow focusing during the karst genesis may be interrupted during dry seasons when the recharge regime is under catchment control. This may cause a stagnation in the evolution of flow channeling or even a less localized flow field. This study highlights the importance of recharge fluctuation in modeling karst genesis, which may have important engineering implications for the management of karst aquifers or the leakage risk prediction at dam sites.