Field experiments were conducted at El-Tina Plain, North Sinai governorate, Egypt, in growing seasons of 2012, 2013 and 2014 to evaluate of design criteria of permanent sprinkler irrigation “PS" under marginal conditions using impact sprinklers with different nozzle diameter and different operating pressure. The other purpose is the response of forage millet yield to seasonal applied water depth and to maximizing the water productivity.Christiansen uniformity coefficient values by different range levels “CUc", irrigation water use efficiency “IWUE", water lost by percolation “DP" and irrigation adequacy “pa" was estimated through field experiments. The randomized complete block design with four replications was used. Experimental treatments consisted of five different sprinkler irrigation uniformity range levels: "CUc1" (90 -95%), "CUc2" (80 - 85%),"CUc3" (70 - 75%), "CUc4" (60 - 65%) and "CUc5" (50 - 55%).The obtained results showed that the maximum value of irrigation adequacy was 69% for CUc1 treatment, while its minimum value (38.8%) was obtained for CUc5 treatment. By increasing irrigation uniformity coefficient, the irrigation adequacy increased, while the water losses decreased. The maximum value of water losses “Dp" was 26.15% for CUc5 treatment, while the minimum value was 7% for CUc1 treatment. By decreasing the irrigation uniformity coefficient "CUc" the high losses of irrigation water "Dp" was caused. Forage millet yield depends on both the application depth of water and the sprinkler irrigation performance, but it is more sensitive to the differences in applied water depth than to the differences in sprinkler irrigation uniformity. Therefore, the good uniformity of the irrigation system under marginal conditions does not mean high forage yield. The methodology of this study could have useful applications in design optimization, management and promotion of permanent sprinkler irrigation system and in deficit irrigation planning under marginal conditions, such as El-Tina Plain.