Accuracy of water application allows reducing average irrigation rate to a level that coincides with soil's hydraulic conductivity and minimizes percolation below the main root zone. Field experiment was conducted to confirm the efficiency of this approach, in a calcareous sandy clay loam soil. The source of irrigation water was ground shallow well. The treatments consisted of three irrigation systems (surface drip (T0) and subsurface drip (T15 and T30), and three levels of irrigation water application at 100, 80 and 60% of crop water requirements (T, 0.8T and 0.6T, respectively). 16 mm drip lines with 0.33-m GR emitter spacing were placed on the furrow ridge surface in the middle of alternative plant rows. Laterals with the same characteristics were buried at two depths (15 and 30 cm) in the subsurface drip irrigation (SDI). The obtained results indicated that the performance of the irrigation system was good throughout the cropping season. Values of statistical uniformity (SU) and distribution uniformity (DU) were 94.8% and 0.93, respectively. The moisture distribution in the soil monitored along plant growthstages indicated that SDI plots produced wider wetted patterns. Under scarce water, (0.8 T and 0.6T) the results demonstrated that SDI exceeded the surface drip irrigation in terms of potato yield and (IWUE). Maximum average yield (12.63 Mg/fed.) was recorded with subsurface drip line buried at 15 cm depth (T15). The overall average yield of potato in the surface drip laterals (T0) declined by 26.9 and 25.1 % compared with SDI (T15) and (T30), respectively. As the applied water decreased from 2209 to 1496.5 m3/fed. by using SDI, the average values of IWUE under SDI were higher than those obtained by surface drip irrigation at any level of applied irrigation water treatments. Thus, in the case of saving 20% of irrigation water, (0.8T15), the highest IWUE value (8.913 kg/m3) was obtained. Meanwhile, the lowest value of IWUE (4.178 kg/m3) was obtained by surface drip irrigation with 100% water application amount level, (T0). This lowest value of IWUE may be reached to 50.5 and 51.7% compared with (T15) and (T30), respectively. In the same time, there was no significant effect for the level of water application on IWUE at (T), (0.8T) or (0.6T) treatments.