How is "Mean Annual Precipitation" calculated for a site evaluation?

Mean Annual Precipitation is determined by averaging measurements taken from a nearby weather station, as this method provides a reliable and standardized way to assess rainfall patterns over time. By utilizing data from a weather station, the evaluation can incorporate extensive historical records that reflect on varying conditions within the specific region.

This approach also allows for the inclusion of systematic data collection methods used by meteorological agencies, ensuring that the information is consistent and has been verified for accuracy. Weather stations are strategically placed to capture data relevant to a broader area, making their readings informative for local site evaluations when establishing mean annual precipitation figures.

While historical rainfall data and local government rainfall reports can contribute to understanding precipitation in an area, they often rely on data collected from weather stations to validate their findings. Agricultural records, while potentially useful, do not provide the comprehensive and systematic approach that weather station measurements do.