This paper presents an irrigation scheduling software named ?Mehran Model? which computes reference evapotranspiration (ETo) using FAO-56 Penman Monteith method and crop evapotranspiration (ETc) by dual crop coefficients. The model can develop irrigation schedules for sixty-six crop types using soil and water balance approach. The model distinguishes soil texture classes, irrigation methods, and designs real time irrigation schedule for a crop using daily weather data of a reference site. The Mehran Model also includes planning on demand basis as well as rotational (warabandi) irrigation schedules, and synchronizes both systems as well. The model has been field tested and validated on planning and management of irrigation schedules for cotton and wheat crops in Lower Indus Basin of Pakistan. Statistical analysis showed that the model at an average overestimated seasonal ETc of cotton and wheat crop by 2.41% and 4.31% respectively.