Basin Characterization Model (BCM)

Science Center Objects

The Basin Characterization Model (BCM) is a simple grid-based model that calculates the water balance for any time step or spatial scale by using climate inputs, precipitation, minimum and maximum air temperature. The BCM can translate fine-scale maps of climate trends and projections into the hydrologic consequences, to permit evaluation of the impacts to water availability at regional, watershed, and landscape scales, as caused by changes in temperature and precipitation.

 

The Basin Characterization Model

The Basin Characterization Model relies on climate input and the rigorous development of potential evapotranspiration to move water through the soil profile and into underlying bedrock to become recharge or runoff. [MPa, megapascal]

Ongoing changes in climate are influencing water resources throughout the world, by reducing snowpack and causing snow to melt earlier in the spring, which are among the most important challenges to water availability. Climate change also impacts landscapes, vegetation and species, and agriculture, by causing longer dry seasons, more frequent extreme storms, fewer chilling hours, and higher snowlines.

Information available to inform land and resource managers is generally composed of model projections of precipitation and air temperature trends with coarse spatial detail. The Basin Characterization Model (BCM) can translate fine-scale maps of climate trends and projections into the hydrologic consequences to permit evaluation of the impacts to water availability at regional, watershed, and landscape scales, as caused by changes in temperature and precipitation.

Scientists divide the landscape into grid cells, each of which uses specific climate data inputs, such as precipitation and air temperature, to solve the water balance for each cell. Model calculations include potential evapotranspiration, calculated from solar radiation with topographic shading and cloudiness; snow, as it accumulates and melts; and excess water moving through the soil profile, which is used to calculate actual evapotranspiration and climatic water deficit—the difference between potential and actual evapotranspiration. Depending on soil properties and the permeability of underlying bedrock, surface water can be classified for each cell as either recharge or runoff. Post-processing calculations are made to estimate baseflow, streamflow, and potential recharge to the groundwater system for watersheds. The model output can define the water balance for any size polygon representing regions or watersheds, or can define the distribution of the various water-balance variables across the landscape.