Understanding the Future Dynamics of the Historic Rice Fields' Ecohydrological Systems Under Changing Climatic Conditions

ABSTRACT Historic rice‐field watersheds in Georgetown County, South Carolina, experience climate‐driven hydrologic changes threatening waterfowl habitat. The reproducible GIS–Python workflow combines HUC‐scale delineation with ArcGIS Pro processing and MACA‐v2 downscaled climate analysis through grouped cross‐validation to measure and explain stream exposure. We used GroupKFold leave‐one‐tributary‐out mixed‐effects modeling and Boruta‐screened random forest/gradient boosting with permutation importance and partial dependence for explainable machine learning. The mid‐century (2030–2059) stream flow patterns increased before showing a slight decrease at the end of the century (2070–2099). The Waccamaw River experienced a discharge increase from 26,851.52 to 30,802.87 m 3 s −1 before its flow decreased to 30,179.38 m 3 s −1 , while the Black River showed the most significant percentage increase at +18.63%. The Coastal Carolina region received its highest precipitation amount of 55.71 ± 2.54 mm. The mixed‐effects model showed that precipitation positively correlates with discharge ( β = 0.136, p = 0.042). The Waccamaw–Atlantic Intracoastal Waterway complex emerged as the most affected area with 28.21% of its stream length classified as affected. The research supports the implementation of riparian buffers, land‐cover management, and adaptive operations, which provide decision‐ready diagnostics to protect water quality and maintain waterfowl benefits during late‐century conditions.