The Multi-Attribute Catchment Hydrology (MACH) dataset contains daily climate forcing data and catchment attributes for 1,014 watersheds across the United States. Climate variables include precipitation, minimum air temperature, maximum air temperature, mean air temperature, snow water equivalent, shortwave radiation, water vapor pressure, day length, potential evapotranspiration, and actual evapotranspiration. Hydrologic data include daily observed streamflow. The primary data record spans 1 January 1980 to 31 December 2023. Catchment attribute categories include land cover, hydrology, geology, soil, regional, climate indices, and anthropogenic characteristics. MOPEX time series data are additionally provided for 395 watersheds for the period 1 January 1948 to 31 December 1979, including precipitation, minimum and maximum air temperature, and observed streamflow. The MACH dataset integrates basins originally defined in the MOPEX and CAMELS datasets using a consistent watershed delineation framework based on NHDPlus Version 2. As a result, basin boundaries and drainage areas in MACH may differ from those reported in the original MOPEX or CAMELS releases, which employed alternative delineation approaches and data vintages. These differences primarily affect area-dependent quantities and may be most pronounced for a small subset of basins. To support cross-dataset comparisons, MACH preserves the original USGS site number (SITENO) for all basins, enabling direct alignment with legacy CAMELS and MOPEX records. Drainage area values derived from MACH (NHDPlusV2/QGIS), along with corresponding drainage areas reported in NWIS and original datasets CAMELS and MOPEX, are provided in the Microsoft Excel file area_differences.xlsx, together with absolute percent differences. This allows users to explicitly account for basin definition differences when conducting area-sensitive analyses. Despite these differences, MACH is fully comparable with CAMELS and MOPEX for most applications, particularly for analyses focused on temporal variability, relative anomalies, and basin-scale hydrometeorological relationships. Users requiring strict consistency in basin area may apply the provided area metrics to normalize variables or restrict analyses to basins with minimal delineation differences. The inclusion of harmonized identifiers, documented area discrepancies, and consistent aggregation procedures enables transparent comparison across datasets while maintaining compatibility with prior studies. Version 4.0 Attribute updates (NHDPlusV2-based attributes) Attributes in anthropogenic.csv, geology.csv, hydrology.csv, regional.csv, and soil.csv were updated for 27 basins following manual reassignment of NHDPlusV2 flowline identifiers (COMID). Reassignments were performed based on visual inspection of gage locations relative to NHDPlusV2 flowlines to resolve drainage area discrepancies. Updated COMIDs are documented in the "COMID_new" column of area_differences.xlsx. Streamflow metadata: In discharge_mach.csv, the total record count, first_date, last_date, and annual completeness metrics were updated. Streamflow data for 2023 were revised in accordance with updates to the USGS provisional data record, resulting in improved data coverage. MACH time series In MACH_ts.zip, daily USGS catchment averaged streamflow values ("OBSQ") were updated for all 1,014 watersheds (last accessed 30 December 2025). Raw discharge data The discharge_cfs.zip archive now includes raw daily USGS streamflow values in cubic feet per second for all watersheds along with USGS data qualification codes (e.g. approved, estimated, provisional). Normalized Difference Vegetation Index The ndvi.zip archive now includes bimonthly NDVI values from GIMMS3G+ for all 1,014 watersheds. Drainage area comparison file The area_differences.xlsx workbook documents original drainage area values from CAMELS, MOPEX, NWIS, and NHDPlusV2, along with MACH-derived geodesic areas and cross-dataset absolute percent differences. Updated COMID assignments and associated NHDPlusV2 cumulative upstream drainage areas (TotDASqKm from the NHDPlusV2 PlusFlowlineVAA table) are provided where realignment occurred. No changes were made to watershed polygon delineations or geodesic basin areas derived in QGIS. All spatial boundaries and drainage areas remain identical to previous versions. Basin delineations are provided in MACH_basins_all.gpkg MACH metadata The README.csv metadata file was revised to reflect all updates introduced in Version 4.0. Version 3.0 README: updated to include the soil_ssurgo.csv attributes Version 2.0 Attributes (site_info.csv): basin 06188000 state abbreviation corrected (MY to WY) Attributes (site_info.csv): basin 06191500 state abbreviation corrected (MY to MT) Attributes (soil_ssurgo.csv): additional soil data added, curated using SSURGO database Attributes (discharge_mopex.csv): added in missing 1948 column, count remains the same MOPEX_ts: csv file for 0163400 data ended 2/15/1967, added missing data MACH_ts: reformatted date column in files to date type, some reading as character. Paper describing the dataset and methods is currently under review. Desktop application: MACH Explorer (Windows executable) available at https://github.com/k-sink/MACHexplorer under releases. This application requires the full_dataset.duckdb file, also available under releases.