DOI: 10.5061/dryad.dv41ns24c
title: Dissolved calcium and pH raster layers for freshwater environments in Canada and the USA

description: Calcium concentration and pH are key parameters that are linked to
 multiple chemical and biological processes in freshwater environments.
 This dataset presents high-resolution (10 x 10 km) interpolated raster
 layers for these two variables across Canada and the continental USA.
 These layers were generated via spatial interpolation (Kriging with a
 fixed zero nugget) after comparison of multiple interpolation methods,
 using water quality data for lakes and rivers compiled from multiple
 sources. This is the first time that such data have been made available at
 this scale and resolution, providing a valuable resource for research,
 including projects evaluating risks from environmental change, pollution,
 and invasive species. 
description: For a detailed description of how the component data were
 assembled, processed, and used to generate interpolated rasters, please
 consult the associated publication.
description: # Dissolved calcium and pH raster layers for freshwater environments in
 Canada and the USA
 [https://doi.org/10.5061/dryad.dv41ns24c](https://doi.org/10.5061/dryad.dv41ns24c) ## Description of the data and file structure The dataset consists of interpolated rasters of freshwater calcium concentration (mg/L) and pH for Canada and the USA. Rasters are available both 'masked' using country outlines, and 'unmasked' to allow users to carry out various transformations or to use their own territory outlines if required. For each interpolated raster, an associated 'kriging variance' raster is provided to provide an indication of the uncertainty in the interpolated values. Data used for the interpolations are also provided; however, some data providers did not give permission for open sharing of their data so these records are not included in the shared files. Detailed metadata documents are provided for each of the database files. #### Rasters All rasters are provided in the North America Albers Equal Area projection (ESRI:102008), at 10 x 10 km resolution, and were generated by zero-nugget kriging. ###### Calcium: 1. calcium-KR-97648-median_10km_ZN_masked.tif: interpolated calcium concentration (mg\L) using median values from 97,648 sites. The raster has been masked using rnaturalearth outlines for Canada and the USA. 2. calcium-KR-97648-median_10km_ZN_variance_masked.tif: kriging variance raster for the above interpolated raster. 3. calcium-KR-97648-median_10km_ZN.tif: interpolated calcium concentration (mg\L) using median values from 97,648 sites. The final resolution is 10 x 10 km. The raster has not been masked. 4. calcium-KR-97648-median_10km_ZN_variance.tif: kriging variance raster for the above interpolated raster. ###### pH: 1. ph-KR-208784-median_10km_ZN_masked.tif: interpolated pH using median values from 208,784 sites. The raster has been masked using rnaturalearth outlines for Canada and the USA. 2. ph-KR-208784-median_10km_ZN_variance_masked.tif: kriging variance raster for the above interpolated raster. 3. ph-KR-208784-median_10km_ZN.tif: interpolated pH using median values from 208,784 sites. The raster has not been masked. 4. ph-KR-208784-median_10km_ZN_variance.tif: kriging variance raster for the above interpolated raster. #### Data ###### Calcium: 1. sites_calcium_85747.csv: temporally-averaged site data used for calcium interpolation. 2. metadata_sites_calcium_85747.csv: metadata document for above data. 3. site-date_calcium_985955.csv: calcium data for each site on all dates with calcium measurements. 4. metadata_site-date_calcium_985955.csv: metadata document for above data. ###### pH: 1. sites_ph_201183.csv: temporally averaged site data used for pH interpolation. 2. metadata_sites_ph_201183.csv: metadata document for above data. 3. site-date_ph_3525217.csv: calcium data for each site on all dates with pH measurements. 4. metadata_site-date_ph_3525217.csv: metadata document for above data. NAs in data files indicate * cases where no unique site identifier was provided in the source data (SITE_ID) * cases where no variability measures (standard deviation, 25th and 75th percentiles) could be calculated because only one record was available, or data were only available for one date (SD,Q25,Q75) Source ID information for above data files: source_ids.csv ## Code/Software Code can be found at the associated GitHub repository: [https://zenodo.org/doi/10.5281/zenodo.10573970](https://zenodo.org/doi/10.5281/zenodo.10573970)