Francisco Guadalupe Echavarría Cháirez

Caracterización hidrológica en un agostadero comunal excluido al pastoreo en Zacatecas, México.II. Escurrimiento superficial

The study was done with the objective of determining losses due to surface runoff in different resource management systems and native plant conditions, and also to estimate some parameters of the hydrological response in the area of study. Three management systems and four predominant native vegetation conditions were studied. Storms with more than 20 mm of rainfall, produced more than 65% of the total water losses in the different systems and vegetation conditions, and the ones with less than 20 mm did not produce significant amounts of runoff even in the conditions of greater plant cover. Water losses in both management systems and native plant conditions were the result of factors interaction such as variability in the time of the daily and annual rainfall (differences of magnitude within and between years), characteristics of plant cover (basal and aerial), rugosity and surface conditions of the soil, which were modified in each site after five years of grazing exclusion. Linear statistical relationships were obtained in order to estimate water loss from individual data of the magnitude of rainfall. Curve numbers (CN) of runoff were estimated for all plant native conditions and management systems. The native vegetation conditions showed differences in CN between extremes values of cover (from 77.3 ± 4.1 to 90.1 ± 1.8). The management systems did not show differences in CN (from 85.9 ± 2.3 up until 87.7 ± 2.3). The derived parameters can be used to feed simulation models that help in the extrapolation of results, strategic planning and decision making, with soil and water conservation criteria.