- The main objective of the study was to assess the relative importance of the electrolyte concentration of rain drops and their kinetic energy on the infiltration rate of naturally crusted loess soil. A highly accurate portable rainfall simulator was used in this study. The effect of electrolyte concentration on infiltration rates was studied by comparing the runoff patterns observed using distilled or tap water. Similar infiltration curves were obtained for both treatments indicating that the effect of the electrolyte concentration of the applied water on infiltration was negligible. The effect of raindrop energy on infiltration rate was assessed by comparing the runoff characteristics of three treatments: fog, plot covered with dense mesh and no-surface protection. No runoff was observed in the fog treatment and the infiltration rates in the protected treatment were significantly higher than those of the unprotected treatment. The results of this study suggest that the momentum of drops hitting a naturally crusted loess soil significantly affect the infiltration process while the electrolyte concentration of the rain water does not meaningfully contribute to further crust development. Runoff coefficients derived from studies carried out with rainfall simulators that do not mimic the natural distribution of drop size and energy should be viewed with care.