Subsurface water retention technology (SWRT) is a new, long-term approach developed to improve water storage capacities of sandy soils for sustainable crop production. It consists of subsurface polyethylene membranes installed within the soil profile that prevent the loss of irrigation water via deep percolation. Our objective was to identify membrane shape and placement to maximize the reduction in irrigation losses. A greenhouse experiment was conducted to measure the distribution of water in a surface-irrigated sand lysimeter with six membranes of different geometry installed at four depths. The HYDRUS-2D model was calibrated using soil water content data to estimate water losses from four soils modified with SWRT membranes. Membranes with 2:1, 3:1, and 5:1 aspect ratios installed at the 20- and 40-cm depths in sand, sandy loam, loamy sand, and sandy loam soils were used in the simulations. Different vertical and horizontal alignments were also tested for the 2:1 membrane aspect ratio. The HYDRUS-2D model adequately described the dynamics of water content measured in the lysimeter experiment. The simulation results showed that the highest reductions in water loss for most studied soil textures were achieved with a 2:1 aspect ratio membrane installed at the 20-cm depth. The SWRT was sensitive to excessive irrigation, and its performance declined rapidly in response to overirrigation. Our modeling results demonstrated a high potential for the SWRT to reduce water losses from the plant root zone. Further testing of membrane performance is needed for different crops in real soils across a range of different climates.