The Food and Agriculture Organization (FAO) CROPWAT 8.0 standard software and the CLIMWAT 2.0 tool affixed to it have been utilized in this study for Qassim Region of Saudi Arabia to find CWRs and irrigation plans for numerous extremely valuable crops of KSA. We were used CROPWAT P. M. method for find out the ETo and (USAD) S. C. method utilized to determine roughly effective rainfall. The analysis demonstrated that ETo change over from 2.84 mm/day in January to reach maximum 9.61 mm/day in July due to high temperature in summer with annual mean was 6.33 mm/day, effective rainfall changes from 0 mm to 53.4 mm. The total IWRs were 308.3 mm/dec, 335.9 mm/dec, 343.6 mm/dec, 853 mm/dec and 1479.6 mm/dec for Barley, Wheat, Maize, Rice and Citrus, respectively. Due to low demand in winter and high demand in summer, the total net irrigation and total gross irrigations are 210.6 mm and 147.4 mm, 176.6 mm and 123.6 mm, 204.5 mm and 143.2 mm, 163.9 mm and 114.7mm for Wheat, Barley, Citrus, and Maize respectively except rice crop. These results showed that Wheat, Barley, Citrus, Maize and Rice crops have 4, 4, 12, 4 and 12 irrigation schedules respectively in a year.