Groundwater depletion driven by anthropogenic interventions has severely compromised the sustainability of traditional water-supply systems. This study employs the GM (1,1) to forecast the discharge dynamics of 213 qanats in a semi-arid basin, overcoming the constraints of short-term time-series data. Results indicated a systematic instability within the hydrological network, evidenced by an average development coefficient of a=0.60. Survival analysis revealed that 24.5% of the studied qanats (55 sources) are projected to reach functional exhaustion by 2036. Spatio-temporal mapping identified a depletion wave propagating from intensive pumping centers toward the basin margins. Although the total aquifer discharge remains relatively stable because of the persistence of a limited number of high-yield qanats, the deterioration of the minor qanat network reflects increasing spatial heterogeneity in the predicted discharge distribution and the gradual degradation of traditional qanat systems. These findings emphasize the necessity of revising hydraulic protection zones and implementing emergency aquifer management measures, including managed aquifer recharge (MAR), in vulnerable areas.