## Breadcrumb

-  Publications 
-  Articles 

#           Predicting regional fluoride concentrations at public and domestic supply depths in basin-fill aquifers of the western United States using a random forest model      

      October 14, 2021    

A random forest regression (RFR) model was applied to over 12,000 wells with measured fluoride (F) concentrations in untreated groundwater to predict F concentrations at depths used for domestic and public supply in basin-fill aquifers of the western United States. The model relied on twenty-two regional-scale environmental and surficial predictor variables selected to represent factors known to control F concentrations in groundwater. The testing model fit R2 and RMSE were 0.52 and 0.78 mg/L. Comparisons of measured to predicted proportions of four F-concentrations categories (<0.7 mg/L, 0.7–2 mg/L, >2 mg/L – 4 mg/L, and > 4 mg/L) indicate that the model performed well at making regional-scale predictions. Differences between measured and predicted proportions indicate underprediction of measured F at values by between 4 and 20 mg/L, representing less than 1% of the regional scale predicted values. These residuals most often map to geographic regions where local-scale processes including evaporative discharge in closed basins or intermittent streams concentrate fluoride in shallow groundwater. Despite this, the RFR model provides spatially continuous F predictions across the basin-fill aquifers where discrete samples are missing. Further, the predictions capture documented areas that exceed the F maximum contaminant level for drinking water of 4 mg/L and areas that are below the oral-health benchmark of 0.7 mg/L. These predictions can be used to estimate fluoride concentrations in unmonitored areas and to aid in identifying geographic areas that may require further investigation at localized scales.

## Citation Information

## Related Content

                  -              Data           
                  -              Connect           

November 2, 2021

####                 Random forest regression model and prediction rasters of fluoride in groundwater in basin-fill aquifers of western United States              

California Water Science Center

#### Celia Rosecrans

##### Hydrologist

California Water Science Center

crosecrans@usgs.gov

916-278-3293

#### Ken Belitz

##### Research Hydrologist

Water Resources Mission Area

kbelitz@usgs.gov

858-775-6309

####             Katherine Ransom (Former Employee)          

##### Hydrologist

California Water Science Center

#### Peter B McMahon

##### Research Hydrologist

Colorado Water Science Center

pmcmahon@usgs.gov

303-236-6899

## Related Content

November 2, 2021

####                 Random forest regression model and prediction rasters of fluoride in groundwater in basin-fill aquifers of western United States              

California Water Science Center

#### Celia Rosecrans

##### Hydrologist

California Water Science Center

crosecrans@usgs.gov

916-278-3293

#### Ken Belitz

##### Research Hydrologist

Water Resources Mission Area

kbelitz@usgs.gov

858-775-6309

####             Katherine Ransom (Former Employee)          

##### Hydrologist

California Water Science Center

#### Peter B McMahon

##### Research Hydrologist

Colorado Water Science Center

pmcmahon@usgs.gov

303-236-6899

### Study Area

### Contact

####               Sacramento Projects Office (USGS California Water Science Center)          

6000 J Street, Placer HallSacramento, CA95819United States

916-278-3000

916-278-3070

####               Colorado Water Science Center - Main Office          

West 6th Avenue and Kipling StreetDenver Federal Center, Building 53, MS-415Lakewood, CO80225United States

(303) 236-6900

(303) 236-4912

####               New England Water Science Center          

10 Bearfoot RdNorthborough, MA01532United States

####               New York Water Science Center          

425 Jordan RoadTroy, NY12180-8349United States

dc_ny@usgs.gov

(518) 285-5695 

(518) 285-5601

### Explore Search

                  - United States
                  - Arizona
                  -  California
                  -  Colorado
                  -  New Mexico
                  -  Nevada
                  -  Utah

View All **