The Qua-Iboe River Basin in Akwa Ibom State, Nigeria,
supports approximately 500,000 people yet its quantitative hydrology remains
uncharacterized. This first comprehensive hydrological assessment integrates
Mann-Kendall trend analysis, Standardized Precipitation Index (SPI) drought
monitoring, and a multi-source surface water budget framework over 2000–2024.
Combined NiMet and CHIRPS precipitation, MODIS MOD16A2 evapotranspiration, and
SWAT/HEC-HMS outputs were cross-validated against GRACE-FO water storage and
GLOFAS discharge. Annual rainfall increased (Sen's slope +19.63 mm/yr, p +2.0) were extremely wet, indicating intensifying
flood hazard. The 25-year mean water budget partitions precipitation (2,162.4
mm) into evapotranspiration (1,361.2 mm; 62.9%), runoff (643.7 mm; 29.8%), and
storage accumulation (+157.5 mm; 7.3%), validated against GRACE-FO (r = 0.81, p
