A Coupled Hydrological–Multi-Criteria Framework for Irrigation Water Allocation in Regulated Canal–Aquifer Systems: Design and Demonstration on TIKEVIR (Hungary)

The Hajdúhát loess plateau in eastern Hungary has no perennial watercourse and overlies a drought-sensitive shallow aquifer, so irrigation supply security and allocation both constrain production. We coupled a dry-2018/wet-2020 MIKE Hydro River model of the East Main Canal (EMC) with a seventeen-year (2009–2025) MIKE SHE groundwater model, and a decision-support layer that couples conveyed-water allocation across sectors with a ranking of management responses. Calibration attains Moriasi Very Good bias-and-balance skill (mean |PBIAS| 1.59%/0.86%), with a head MAE of 1.431 m over 132 wells, and continuous validation reproduces measured discharge to within −7.7% bias over 2022–2025. Growing-season evapotranspiration (448 mm) exceeds precipitation (309 mm), leaving a 314 mm unsaturated-zone deficit; the dry-year canal terminus shows 34 of 92 no-flow days and a sustainability index of 0.09, against 0.34 when wet. A reconciled reach × sector balance and an isolating hydraulic test show the deficit is an allocation problem, not a conveyance limit. A Leopold/analytic-hierarchy-process ranking favors priority-ordered allocation over new capacity, and, in a two-objective time–quantity allocation, re-timing 8.57 × 106 m3 of fish-pond filling into winter would remove the spring deficit without new infrastructure. Dry-year supply is thus a problem of allocation and timing as much as of capacity.