Seasonal changes of the infiltration rates in a Mediterranean scrubland on limestone

To investigate the seasonal changes of infiltration rates, measurements by means of simulated rainfall experiments and cylinder infiltrometer were done in a small E-W oriented watershed in Southeast Spain. Data were collected during both the wet seasons (autumn, winter and spring) and the dry season (summer). Infiltration rates were very high in summer, when direct surface runoff is very low. During the wet seasons, the infiltration rates were lower due to the increase in soil moisture. Measurements by means of both pending as well as simulated rainfall are suitable to study the infiltration process. The former needs more replications, due to the small observation area encompassed for each experiment. Rainfall simulation experiments are more realistic and accurate, but also more sophisticated and costly. The rates measured by means of a cylinder infiltrometer were 8.5 times higher than by simulated rainfall at an intensity of 55 mm h(-1). Under simulated rainfall it was found that the soils with lower infiltration rates have greater seasonal infiltration changes. The soils of the north-facing slope always show high infiltration rates (49 mm h(-1)), while those of the south-facing slope have lower infiltration rates (27 mm h(-1)). Seasonal changes of infiltration rates play an important role in soil and slope hydrology in semiarid environments. During summer surface runoff was not observed on vegetation covered soils, and runoff rates were only 10% of the rainfall on the bare surfaces. During the wet season, especially in autumn, runoff coefficients were equal to 0.3 on bare surfaces, and on the vegetated surfaces runoff was negligible.