Freshwater scarcity is a critical constraint on global agriculture, with arid regions such as Saudi Arabia facing acute challenges as farming consumes most of the available water. This study evaluated the performance of a dual-lateral subsurface drip irrigation (SDI) system using fresh and brackish water for potato and tomato production under hyper-arid conditions. Over three growing seasons, six irrigation strategies combining simultaneous and sequential operation of fresh and brackish water were tested in a factorial design. Results showed that irrigation water quality and operation mode significantly affected crop response. For potatoes, yield and water productivity were highest under simultaneous application, while brackish-dominated sequences reduced performance. Tomatoes exhibited higher salt tolerance, maintaining yield across treatments, though water productivity and footprint varied with operation sequence. Overall, dual-lateral SDI with concurrent operation demonstrated superior efficiency, reducing dependence on freshwater while sustaining crop yields. These findings highlight the potential of dual-lateral SDI as a sustainable irrigation strategy for water-scarce regions.