User story: as a surface water hydrologist, I need quick access to computed historic percentile data are calculated using citable and trusted methods.

• Create methods documentation for statistics used for percentile calculations
• Define the approach for calculating percentile statistics. This should serve as the reference for hydrologists who are using these data. When existing services are used, identify methods and ensure they have passed Fundamental Science Practices (FSP).
• Enable mapping of percentiles by a UI: provide raw percentiles and categories ('bins') using commonly accepted thresholds. his feature will enable downstream users to create national-scale maps.
• Provide an example in the Documentation for how to generate a real-time, national-scale map with sites colored by percentile value

1. Pull NWIS data of current streamflow
2. Calculate historical percentile values for all sites with current conditions for the day of the year on daily, 7-day, 14-day, 28-day average timescales
3. Create a standardized data output to enable downstream mapping of data and percentile values at the site, state and HUC2 scales

Considerations:

• need to handle negative flows

Nice to have:

• filtering dataset to the HCDN network, as per Xiaodong Jian recommendation

References: https://waterwatch.usgs.gov/index.php?id=real