Reach-scale LCOE of run-of-river hydropower under glacier retreat and winter ice in the Tien Shan

Run-of-river small hydropower (SHP) can electrify off-grid mountain communities in Central Asia, but national assessments rely on coarse runoff grids and fixed capacity factors. We assess 949 reaches of the glacierised Sary-Jaz basin (Tien Shan, Kyrgyzstan) by combining twelve winters of Sentinel-1 backscatter to detect river ice, a degree-day discharge model forced by ERA5-Land and CHIRPS, and a levelised cost of electricity (LCOE) framework. Energy is computed from a screening capacity factor or simulated daily flow, and uncertainty is examined with Monte Carlo, multi-SSP and lifetime analyses. Screening LCOE without ice is 72–544 USD/MWh (median 147). Without ice, the 20–50% glacier-fraction class is cheapest (139.5 USD/MWh), but SAR-derived ice derating shifts this to the 5–20% class (146.7 versus 152.3 USD/MWh). The shift persists with flow-based energy (156.8 versus 162.7 USD/MWh) and needs a shutdown fraction of only 0.00–0.14. Because simulated winter flow mostly falls below the minimum turbine flow, this derating is an upper bound; with generation-weighted derating the classes are tied at present, but the 5–20% class remains cheaper in all eight SSP snapshots. With reach-level cost uncertainty, it is cheaper in 63% of 2000 Monte Carlo realisations, a probable tendency rather than a certainty. Under SSP2-4.5, the 50–100% class loses 24% of its design discharge by 2080; its lifetime LCOE rises from 173 to 180 USD/MWh between commissioning years 2030 and 2050, whereas the 5–20% class stays near 152 USD/MWh. No reach approaches the ≈46–52 USD/MWh feed-in tariff; tariff reform or concessional finance is required.