Susquehanna River at Harrisburg, PA


USGS gage 01570500 has been operating since 1890. This incredible 130 year period of record is a great resource for hydrologists. I pulled daily flow data from this period of record to put recent flow years into context.

How does 2020 stack up?

2020 was dry in the northeast US. I was wondering how river flows were compared to past years. The below graphic allows you to compare years interactively. The left pane shows yearly average daily flow sorted from high to low. The right pane shows hydrographs of yearly flow. You can select a year to view by clicking on either plot, or entering a year from the selection box. You can select additional years by holding down the shift button on your keyboard.

Annual Flows


JASON Months


However, the melt/rain event at the end of 2020 was the highest flow event of the entire year. Flows went from ~9,000 to nearly 300,000 cfs in only 5 days!. If we look only at the traditionally dry months of July - November (the JASON months), how does 2020 compare? The below plot is identical to the graphic above, but just for this condensed time period.

How does 2020 rank?


How does 2020 rank compared to the 130 year period of record? We’ll also throw in 2016, another dry year in recent memory.

  • For the full year:
    • 2020 - 48th driest
    • 2016 - 11th driest
  • For JASON months:
    • 2020 - 20th driest
    • 2016 - 27th driest


2020 was actually drier than 2016 in the July - November period!


See the table below for a full list of the rankings. You can sort by Annual or JASON timeframes. 1 is driest – 130 is wettest.


I’ll leave you with an image of the Susquehanna in all her glory, courtesy of the International Space Station. The gage used in this analysis is just south of the image extent.