Great Basin 200-meter Basin Characterization Model (BCMv8) - Monthly Historical Climate and Hydrology for water years 1896-2025

The Great Basin of the United States of America (USA) spans nearly all of Nevada, much of Utah, and parts of Arizona, California, Oregon, Idaho, and Wyoming. The Basin Characterization Model (BCM) version 8 (v8; described in Flint and others, 2021) for the Great Basin is 200 by 200-meter spatial resolution with monthly intervals ranging from water years 1896 to 2025. This data release includes downscaled Great Basin BCM gridded climate inputs, hydrologic outputs, and a model archive. Downscaled gridded climate inputs include: precipitation (ppt), minimum temperature (tmn), maximum temperature (tmx), and potential evapotranspiration (pet). Gridded hydrologic variables include: actual evapotranspiration (aet), climatic water deficit (cwd), snowpack (pck), recharge (rch), runoff (run), and soil storage (str). The units for temperature variables are degrees Celsius, and all other variables are in millimeters. Monthly historical variables from water years 1896 to 2025 are summarized into water year files and long-term average summaries for water years 1961 to 1990, 1981 to 2010, and 1991 to 2020. Raster grids are in the North American Datum of 1983 (NAD 1983) Contiguous USA Albers (meters; European Petroleum Survey Group (EPSG) 5070 NAD 83 Conus Albers) projection in an open format ascii text file (*.asc). Data are organized into: 1. 30-year summaries, 2. Model Archive, 3. Monthly climate variables, 4. Monthly hydrology variables, and 5. Water year summaries.

This BCMv8 model was developed and calibrated at the regional scale of the Great Basin. At this scale, model parameters are adjusted to provide the best fit to hydrologic targets and observations aggregated over relatively large areas. The authors consider the resulting broad spatial distribution and large-scale temporal variability of in-place recharge and runoff to be representative of historical conditions. Regional calibration of the Great Basin BCM minimizes simulated errors across the model domain. However, because the model uses regionalized representations of bedrock geology and vegetation types, simulated errors may be positive in some watersheds and negative in others. These errors can offset one another at the regional scale, resulting in a minimized apparent error for the model domain as a whole.

Because simulated errors in the Great Basin BCM can vary in magnitude and direction at the local scale relative to regional-scale results, the recommended best practice for using the model provided in this data release is to extract relevant subareas and perform localized calibration. Localized calibration can incorporate site-specific knowledge and improve estimates of recharge and runoff, providing a more robust basis for comparison with independent estimates of local basin-scale water budgets.