Total Deposition Maps

One of the goals of the NADP Total Deposition (TDEP) Science Committee is to provide estimates of total sulfur and nitrogen deposition for use in critical loads and other ecological assessments.

The deposition estimates provided here were developed using an approach that combines measured air concentration and wet deposition data and modeled deposition velocity and dry deposition data. Wet deposition values are obtained from combining the National Trends Network (NTN) measured values of precipitation chemistry with precipitation estimates from the Parameter-elevation Regression on Independent Slopes Model (PRISM). Air concentration data from the Clean Air Status and Trends Network (CASTNET), the Ammonia Monitoring Network (AMoN), and the SouthEastern Aerosol Research and Characterization (SEARCH) network were included. Modeled data were obtained from the Community Multiscale Air Quality (CMAQ) model.

Details of the methodology for developing the data set as well as comparisons of deposition from this data set with other deposition estimates is provided in Schwede and Lear (2014). This data set is expected to be updated as the methodology evolves and as new data become available. Each version is denoted by a version number which includes the four digit year of release and a two digit version number. For example, the current release is version 2016.01 and contains files for the years 2000-2015. The data are available as ESRI ArcGRID exported gridded deposition fields and maps that can be downloaded using the links below.

Questions about the data should be directed to Donna Schwede ( or Gary Lear (