Skip to main content

Table 3 Agreement* between nitrate measures, overall and by type of water source

From: Water quality monitoring records for estimating tap water arsenic and nitrate: a validation study

  Radius (maximum distance between residence and water source, miles)
  0.5 1 2 3 4 5 6 7 8 9 10
All residences (N = 105)            
% with monitoring data in radius 50 72 87 92 94 98 100 100 100 100 100
Agreement*            
All sources in radius            
   Mean 0.49 0.44 0.39 0.34 0.34 0.30 0.32 0.32 0.31 0.32 0.34
   Maximum 0.37 0.37 0.27 0.26 0.28 0.28 0.33 0.29 0.29 0.29 0.25
   Most recent 0.38 0.17 0.31 0.32 0.25 0.27 0.31 0.30 0.28 0.21 0.18
Closest source only            
   Mean 0.34 0.32 0.25 0.25 0.25 0.24 0.25 0.25 0.25 0.25 0.25
   Maximum 0.19 0.26 0.19 0.20 0.19 0.21 0.20 0.20 0.20 0.20 0.20
   Most recent 0.35 0.33 0.24 0.24 0.23 0.22 0.21 0.21 0.21 0.21 0.21
Residences on a public system† (N = 87)            
% with monitoring
data in radius
47 72 87 92 94 99 100 100 100 100 100
Agreement* (mean, all sources in radius) 0.49 0.39 0.35 0.29 0.29 0.24 0.29 0.30 0.28 0.31 0.35
Residences with a private well‡(N = 18)            
% with monitoring data in radius 61 72 83 94 94 94 100 100 100 100 100
Agreement* (mean, all sources in radius) 0.14 0.60 0.40 0.51 0.47 0.44 0.47 0.46 0.43 0.41 0.40
  1. * Correlation (Spearman's rho) between nitrate levels measured in tap water of individual residences and selected summary measures for that home estimated using public water quality monitoring data and geographic information systems (GIS).
  2. Water system served by wells, surface sources or other sources with federally-mandated monitoring.
  3. ‡ Individual or shared private well, not subject to federally-mandated monitoring.