The map above displays locations of the 3,602 lakes included in the Georeferenced Lake Nutrient Chemistery (GLNC database). The button at the top right corner of the map also allows one to view locations of lakes with data for 6 selected parameters (NO3-N, NH4-N, PO4-P, TN, TP, chl a). A total of 28 parameters are included in the GLNC database. On the map, the marker for each lake represents the center of the lake, not a specific sample location. Labels for each lake marker include the NHDPlus v2 COMID and loc_name.
A COMID is a unique number assigned to each lake in the U.S. by NHDPlus v2. However, some small mountain lakes with chemistry data in the GLNC database are not included in NHDPlus v2. For these lakes, the COMID value displayed on this interactive map and in the GLNC database (COMIDs 1-596) were assigned for the purposes of creating the database, and are unique to the GLNC database within NHDPlus v2 regions 10-18. The GLNC database also includes a shapefile with lake polygons and COMIDS, which can be used to join to NHDPlus v2 and thereby obtain NHDPlus v2 hydrologic data for each lake in NHDPlus v2 regions 10-18.
On lake markers, values of loc_name are sample location descriptions provided by one data source that included chemistry data for the lake. Hoever, note that lake markers on the interactive map represnet the center of the lake, not a sample location. For many (but not all) lakes, loc_name corresponds to the lake name. Because there may be multiple sample locations for a lake within or accross sources, there can be more than one loc_name per COMID. However, only one loc_name is displayed per lake on the lake marker for simplicity. In many cases, mountain lakes do not have names in NHD, or lake names were recorded slightly differently accross sampling efforts, so selecting a lake name to display on the map is not simple. NHDPlus v2 includes a lake name field (GNIS_NAME) that is included in the GLNC database, but it was not used for labeling lakes on the interactive map because the GNIS_NAME field is blank for the majority of small mountain lakes accross the Western U.S.
This map is provided solely to enable users to explore lakes included in the database. Note that many factors that are not incorporated into the map (sample year, sample depth, etc) may affect the number of lakes in the GLNC database relevant to a particular application. Users should consult Williams and Labou (2017) and associated files for information about nutrient chemistry data available within the GLNC database.
Williams, J.J. and Labou, S.G. 2017. A Database of Georeferenced Nutrient Chemistry Data for Mountain Lakes of the Western United States. Scientific Data (in press).
GLNC database data are available at: https://doi.org/10.6084/m9.figshare.4578544
Abstract: Human activities have increased atmospheric nitrogen and phosphorus deposition rates relative to pre-industrial background. In the Western U.S., anthropogenic nutrient deposition has increased nutrient concentrations and stimulated algal growth in at least some remote mountain lakes. The Georeferenced Lake Nutrient Chemistry (GLNC) Database was constructed to create a spatially-extensive lake chemistry database needed to assess atmospheric nutrient deposition effects on Western U.S. mountain lakes. The database includes nitrogen and phosphorus water chemistry data spanning 1964-2015, with 148,336 chemistry results from 51,048 samples collected across 3,602 lakes in the Western U.S. Data were obtained from public databases, government agencies, scientific literature, and researchers, and were formatted into a consistent table structure. All data are georeferenced to a modified version of the National Hydrography Dataset Plus version 2. The database is transparent and reproducible; R code and input files used to format data are provided in an appendix. The database will likely be useful to those assessing spatial patterns of lake nutrient chemistry associated with atmospheric deposition or other environmental stressors.