Feature Transformation

Feature transformation was carried out to ensure that variables were more informative and suitable for model training. Categorical variables such as major river basin (MRB) and dominant land cover (DLC) were encoded with unique integer values to represent each class. For MRB, the HydroSHEDS-provided HYBASID was used as the unique identifier (Lehner et al., 2008).

Several continuous variables exhibited high skewness, particularly those related to spatial dimensions (e.g., capacity, area, and length). To address this, a natural log transformation was applied. The original abbreviations and variable names were retained after transformation to ensure consistency across tables and figures.

Additionally, negative values of sedimentation rate (SR)—which can arise from sediment management interventions or short observation periods (Minocha and Hossain, 2025a)—were replaced with small nonzero values (0 MCM/year). This adjustment ensures that the models do not attempt to learn physically implausible negative values, while still preserving the integrity of the dataset.

Log-Transformed Features

The following variables were transformed using the natural logarithm. Original feature numbers and abbreviations have been retained for consistency.

No.	Name	Abbreviation
P1	Original Built Capacity	log_OBC
P2	Dam Height	log_HGT
P6	Reservoir Area	log_RA
P7	Reservoir Perimeter	log_RP
P8	Flow Length	log_FL
P9	Catchment Area	log_CA
P10	Differential Catchment Area	log_DCA
P14	Land cover of artificial surfaces	log_LCAS
P15	Land cover of cropland	log_LCC
P16	Land cover of grassland	log_LCG
P17	Land cover of trees	log_LCT
P18	Land cover of shrubs	log_LCS
P19	Land cover of herbaceous vegetation	log_LCHV
P20	Land cover of mangroves	log_LCM
P21	Land cover of sparse vegetation	log_LCSV
P22	Land cover of bare soil	log_LCBS
P23	Land cover of snow and glaciers	log_LCSG
P24	Land cover of water bodies	log_LCWB
P36	Mean Annual Inflow	log_MAI
P37	Peak Annual Inflow	log_PAI
P39	Standard Deviation in Inflow	log_I_std
P42	Mean Annual Outflow	log_MAO
P43	Standard Deviation in Outflow	log_O_std
P47	Mean Surface Area	log_SA_mean
P48	Standard Deviation of Surface Area	log_SA_std
P51	Kurtosis of Surface Area	log_SA_kurt
P52	Mean Surface Area (clipped)	log_SA_mean_clip
P62	Mean Annual Rainfall	log_MAR
P74	Relative Original Capacity	log_ROBC
P75	Geometry Complexity	log_GC
P82	Rainfall per Unit Area	log_rain_per_area
P83	Trapping Efficiency	log_TE
P84	Residence Time	log_RT
P85	Estimated Capacity Loss Rate	log_ECLR
P86	Estimated Sedimentation Rate	log_ESR
P87	Sediment Influx	log_SIN
P88	Sediment Outflux	log_SOUT