Increasing agricultural productivity without undermining further the integrity of the Earth’s environmental systems such as soil water balance are important tasks to ensure food security for an increasing global population in rainfed agriculture. The impact of intercropping maize (Zea mays L.) with potato (Solanum tuberosum L.) on yield, land equivalent ratios (LER), water equivalent ratio (WER), water use, energy output, and net economic return were examined under seven planting systems: potato grown solely or intercropped on theflatfield without mulching, maize grown solely or intercropped with potato on ridges orflatfield with or without plasticfilm mulched. The three intercropping systems had 3–13% less water use than the monocropping. Among the intercropped systems,flatfield caused more depletion of soil water than ridgedfield for both years. Compared to monocultures, intercropping with plasticfilm mulching and ridging significantly increased LER and WER. Meanwhile, intercropping with mulching and ridging significantly increased net economic return and energy output by 8% and 24%, respectively, when compared to monocropping. These results suggest that maize under plasticfilm mulched ridge-furrow plot intercropped with potato underflat plot without mulching increased energy output, net economic return, and water use efficiency without increasing soil water depletion, which could be an optimal intercropping system for the semiarid farmland on the western Loess Plateau.