["Australian Journal of Agricultural and Resource Economics, EarlyView. ", "\nABSTRACT\nChina's irrigated heartlands face concurrent pressures of aquifer depletion and grain security. We evaluate Hebei's Substituting Groundwater with Surface Water for Irrigation (SGSWI) project—a medium‐scale, short‐haul program—using county‐level panel data and a staggered difference‐in‐differences design that combines water accounts, monthly deep/shallow groundwater levels, meteorological controls and agricultural statistics, supplemented by village/household surveys. We find that the SGSWI project rebalances irrigation sources without raising total agricultural water use: surface water rises by 3.2%, whereas groundwater falls by 2.3%. The program benefits deep aquifers—deep withdrawals decline 5.3% and the depth to the deep water table recovers by 1.85 m—with no detectable effect on shallow systems. Regarding production, grain output increases 8.3%, driven by a 7.4% expansion in sown area and a 3.7% rise in the multiple‐cropping index; yields per unit area, water‐use efficiency and fertiliser use intensity remain unchanged. Effects are larger where projects connect to inter‐provincial transfers and in severely overdrafted counties; dual‐source counties show the biggest output gains but risk rebound in total water use. A recipient‐side cost–benefit accounting yields an internal rate of return (IRR) of 11.55%, with one‐way sensitivity checks showing only moderate sensitivity to groundwater valuation, operational and maintenance (O&M) costs, and tariffs but strong sensitivity to shortfalls in realised transfer volumes. Sustainability, however, is constrained by supply uncertainty, weak inter‐regional coordination, incomplete infrastructure, underdeveloped operation and maintenance and underpricing. Policy priorities include targeting severe overdraft basins, locking in multi‐year delivery commitments, completing and funding ‘last‐mile’ assets, introducing volumetric and tiered tariffs with safeguards and strengthening aquifer‐specific monitoring and accountability.\n"]