Large-scale rainfall simulation over shallow caves on karst shrublands

Within semi-arid landscapes, karst areas are among the most productive in terms of water supply-largely because of the high rates of groundwater recharge compared with those of other semi-arid areas. Recharge rates in karst regions may be affected by the type of vegetation cover. Understanding the interactions between recharge and vegetation is important at many levels, but the complex nature of karst hydrology makes this endeavour challenging. This paper presents the results of a set of hillslope-scale rainfall simulation experiments conducted within a juniper-oak woodland and over a shallow karst cave that was instrumented for drip-rate monitoring. The variables measured during these experiments include the amounts and timing of cave recharge, surface runoff, stemflow, and throughfall. The findings of this study provide insights into the importance of canopy interception during runoff-producing events, the nature and relative magnitude of rapid recharge, and the interplay between recharge and surface runoff. Key findings of the study were (1) for simulated rainstorms of around 50 mm, between 0 and 23% of the water applied was intercepted (depending on cloud conditions), and 4-9% of the water reaching the ground surface came from stemflow (which was highest under the wettest conditions); (2) surface runoff accounted for approximately 3% of the water applied; and (3) recharge accounted for between 8 and 17% of the water applied and typically reached its maximum level within 20 min of rainfall cessation, declining rapidly thereafter. Copyright (C) 2009 John Wiley & Sons, Ltd.