Imagine tracking a child’s growth if your measuring tape had no inch markings. 1 ft, 2 ft, 2ft, 3 ft, 3 ft, 3ft

Not very helpful is it? The same thing could happen if you were trying to measure a gradual decline in nitrate with a Hach test strip, which measures in very course increments: 10 mg/L, 10 mg/L, 10mg/L, 5 mg/L, 5mg/L

For this reason, I’ve always assumed that trend monitoring is not a realistic use for volunteer monitoring data. However, that wrongly assumed that any year-to-year trends would be small and gradual. Instead, using weekly lab data, I’ve found several big swings in nitrate over the past 20 years. It turns out volunteers with the Squaw Creek Watershed Coalition tracked some of the same trends. These six sites were sampled monthly from 2002 to 2008. Trends at three sites were even statistically significant, at the 90% confidence level.

Nitrate trends as measured by volunteers with the IOWATER program.