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Sentinel Site Criteria

This criteria is suggested by NGRREC/GLTG. It will be updated with revision and suggestions from partners. - for discussion/to be updated

1. Parameters of interest (do not all have to occur at a single site)
   1. Nitrate
   2. TN
   3. Total Phosphorus
   4. Dissolved Phosphorus
   5. Turbidity
   6. Sediment (If viable. Likely few sites available)
2. Site Criteria
   1. Data / Measurements
      1. Longest record available. Data going back to 1980, time series may be shortened slightly if list of sites too narrow.
      2. At least monthly sampling, more frequent is better
      3. Discreet and Continuous sensor data should not be mixed unless an analysis is done to determine if data is comparable
      4. Gaps in data should be fairly short in duration
      5. Event data, if available, can be used, though is not necessary*
      6. If methods vary between sites, can still compare as long as an approved method used, and parameter reported is the same
      7. When using WRTDS, flux bias statistic should be in range of -0.1 to 0.1
      8. Flow measurements(discharge) should be available either at the site, or close by on the waterway, to be used to calculate loads
      9. Data gaps should be relatively short, no more than one to two years- use as screening criteria to select sites with shortest data gaps
      10. Baseline 1980-1996?
   2. Geographic
      1. Between approx 1000 sq mi to 20,000 sq mi (no smaller than HUC 8, approximately size of HUC 6)
         1. HUCs not necessarily the size of the watershed.
         2. Drainage for site should be specifically calculated and mapped
      2. Watershed land use should be approximately representative of the state’s land use
      3. Small watersheds (HUC 12 size) are more relevant to a particular project, not necessarily state-level progress
      4. Sites experiencing backwater flow should generally be avoided
3. Methods
   1. Loads
   2. Flow-Normalized Loads & Trends
      1. WRTDS
         1. If interested only in NPS, then remove point source discharges

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*  Event data may not bias WRTDS, but make the trends calculated using the method less reliable. (need citation)

Selected Sentinel Sites

Each sentinel site will have a separate page. This section will summarize the sites.