Box-and-whisker plots provide a statistical summary for a single set of data; in this case, a single sampling site on the Truckee River (sites T1, T2, T3, T4). On the plot, N = # means the number of samples that were collected for the parameter over time at the site.
The boxes representing data for each sampling site are cut by a horizontal line, which represents the 50th percentile (median).
The top of the upper box represents the 75th percentile and the bottom of the low box represents the 25th percentile of the data set. The diamond shows the mean value.
Either the mean or median value can be referred to as the “average,” so any discussion of “the average concentration” should specify which statistical quantity (mean or median) is being used to represent the “average” concentration.
The whiskers extend down from the 25th percentile to the minimum concentration, and up from the 75th percentile to the maximum concentration.
Indicator Gauge Icon Legend
Legend Colors
Red is bad, green is good, blue is not statistically different/neutral.
Compared to Distribution
the value is in the best half of communities.
the value is in the 2nd worst quarter of communities.
the value is in the worst quarter of communities.
Compared to Target
meets target; 
does not meet target.
Compared to a Single Value
lower than the comparison value;
higher than the comparison value;
not statistically different from comparison value.
Trend
non-significant change over time; 
significant change over time; 
no change over time.
Compared to Prior Value
higher than the previous measurement period;
lower than the previous measurement period;
no statistically different change from previous measurement period.
Significantly better than the overall value
Significantly worse than the overall value
No significant difference with the overall value
No data on significance available
Truckee River Average Yearly Total Nitrogen
This indicator is archived and is no longer being updated. Click to learn more
Truckee River annual average monitoring samples (total milligrams/liter) to determine if the river is meeting water quality standards established for the Total Maximum Daily Loads for Phosphorus, Nitrogen and dissolved solids set under Section 303 of the Clean Water Act. Maximum annual average anti-degradation = 0.3 mg/l; annual average beneficial use at Vista/Lockwood = 0.75 mg/l (nitrate standard for drinking water is 10 mg/l; nitrate is a component of the total nitrogen load).
Note that samples are not collected every month each year, and include storm, flood and drought years. [Site nutrient and TDS data analysis were discontinued in 1999 for the station @ E. McCarran Bridge. Vista Gage was discontinued for restoration work in 2011, and moved from the station above Lockwood to @ Lockwood/T4 in 2012.]
Why is this important?
The Nevada Division of Environmental Protection (NDEP) oversees compliance with the Federal Clean Water Act and conducts a comprehensive water quality analysis every two years to identify impaired waterbodies and create a priority list for which plans are needed to restore water quality. River pollutants or stressors include temperature, total Phosphorus, total Nitrogen, turbidity and many other impairments. In low water years, we often see water quality improve because less water carries fewer pollutants into the river. Expect to see increased levels of pollutants in years with wet winters.
Total Nitrogen milligrams per liter (annual average monitoring samples per testing station)
| Testing Station | Source | Measurement Period | Total Nitrogen milligrams per liter (annual average monitoring samples per testing station) | |
|---|---|---|---|---|
Data Source
- Nevada Division of Environmental Protection
Note: This source uses Zip Code Tabulation Areas (ZCTAs) for its Zip Code data. Learn more
Maintained By: Truckee Meadows Tomorrow
Filed under: Environmental Health
NEDP Preferred Data Graph - Box and Whiskers Plot for Nitrogen
The side-by-side box-and-whisker plots show data from four sampling sites (T1, T2, T3, T4) for easy comparison. In this case, the plots show that both the mean and median concentrations for total nitrogen increase from upstream (T1) to downstream (T4).
Average Yearly Total Nitrogen (N mg/L) in the Truckee River
One Truckee River Testing Stations Map
Click on the map to view testing stations