streamstats_watershed.R

library(jsonlite);library(sf);library(sp);library(geojsonio)

watershed = function(state, lon, lat, sf=TRUE){
  p1 = 'https://streamstats.usgs.gov/streamstatsservices/watershed.geojson?rcode='
  p2 = '&xlocation='
  p3 = '&ylocation='
  p4 = '&crs=4326&includeparameters=false&includeflowtypes=false&includefeatures=true&simplify=true'
  query <-  paste0(p1, state, p2, toString(lon), p3, toString(lat), p4)
  mydata <- fromJSON(query, simplifyVector = FALSE, simplifyDataFrame = FALSE)
  poly_geojsonsting <- toJSON(mydata$featurecollection[[2]]$feature, auto_unbox = TRUE)
  if(sf){
    poly <- st_read(poly_geojsonsting, quiet=T)
  }else{
    poly <- geojson_sp(poly_geojsonsting)
  }
  poly
}

#Example: Delineate Calapooia River, OR
lon = -123.1121
lat = 44.6390
state = 'OR'

#Watershed example as sp object
ws = watershed(state, lon, lat, sf=F)
plot(ws, col='red')

#Watershed example as sf object
ws = watershed(state, lon, lat, sf=T)
plot(ws$geometry, col='red')