EVALUATION OF HYDROLOGICAL PARAMETERS FOR DESIGN OF MICROCATCHMENT WATER HARVESTING IN A SEMI-ARID CLIMATE

Most parts of Iran are located in arid or semi-arid regions with low amounts of rainfall and a moderate-to-high potential of runoff. The microcatchment water harvesting (MCWH) system could store more runoff water in the soil of the root zone of trees and improve their growth. This study was carried out to evaluate the hydrological parameters for microcatehment design, taking into account (i) rainfall, runoff, soil moisture holding capacity and tree water consumptive use relationships, and (ii) the long term runoff behavior of the control, compacted and chemically-treated microcatchments. The results indicate that surface mulching with cationic emulsion of petroleum mulch of 10000 lit/ha was not effective in increasing surface runoff. Furthermore, mechanical compaction of the soil surface was only effective in increasing runoff during the First year of experiment and resulted in a runoff coefficient of the proportionality of 0.056 vs. 0.04 for the non-compact surface. The proportionality coefficient of runoff increased to ahout 0.09 in later years. Furthermore, an area-dependent equation for annual runoff efficiency was used to presenl nonnograph for determination of the annual runoff depth with selected recurrence intervals. Thus, the annual runoff could he used in the design of microcatchment size at given annual rainfall, soil water holding capacity, root depth and the consumptive use of a tree.