Ohio Nowcast.
How did the nowcast system perform in past years?

Huntington - How did the nowcast perform in past years?At Huntington, nowcasts were provided to the public for 697 days during the recreational season of 2006-13.

  • The nowcast provided a correct response 85.1 percent of time.
  • The sensitivity of the nowcast was 60.5 percent. That means that the nowcast correctly predicted that the standard was exceeded on 72 out of 119 days that the standard was actually exceeded.
  • The specificity of the nowcast was 90.1 percent. That means that the nowcast correctly predicted that the standard was NOT exceeded on 521 out of 578 days that the standard was actually NOT exceeded.

The Huntington nowcast continues to provide more accurate information and better estimates of public health risk than the use of the previous day’s E. coli (the current method used by most beach managers.), especially in regard to sensitivity. In addition, nowcast results have been consistent from year-to-year.

  • The previous day’s E. coli provided a correct response 74.9 percent of time.
  • The sensitivity of using the previous days E. coli was 23.4 percent. That means that the current method correctly predicted that the standard was exceeded on only 25 out of 107 days that the standard was actually exceeded.
  • The specificity of using the previous days E. coli was 85.4 percent, slightly lower than using the nowcast.
Huntington Beach Nowcast Results (2006-2013).

At Edgewater, nowcasts were provided to the public for 693 days during the recreational season of 2008-13.

  • The nowcast provided a correct response 75.6 percent of time.
  • The sensitivity of the nowcast was 59.2 percent. That means that the nowcast correctly predicted that the standard was exceeded on 90 out of 152 days that the standard was actually exceeded.
  • The specificity of the nowcast was 80.2 percent. That means that the nowcast correctly predicted that the standard was NOT exceeded on 434 out of 541 days that the standard was actually NOT exceeded.

The Edgewater nowcast provided more accurate information and better estimates of public health risk than the use of the previous day’s E. coli (the current method used by most beach managers.). Although the sensitivity of the nowcast was greatly improved over the previous day’s E. coli, the specificity was about the same using the nowcast and the previous day’s E. coli concentrations.

  • The previous day’s E. coli provided a correct response 71.4 percent of time.
  • The sensitivity of using the previous days E. coli was 34 percent. That means that the current method correctly predicted that the standard was exceeded on only 49 out of 144 days that the standard was actually exceeded.
  • The specificity of using the previous days E. coli was 81.6 percent, about the same as using the nowcast.
  • Work will continue in 2014 to improve the accuracy of the Edgewater nowcast. These include measurements of foreshore head and photosynthetically-active radiation and qPCR results.
Edgewater Beach Nowcast Results (2008-2013).  

 

At Maumee Bay State Park, nowcasts were provided to the public for 49 days during the recreational season of 2013. The nowcast was able to provide more correct responses (79.6%) than the use of the previous day’s E. coli (64.7%) and both a higher sensitivity and specificity.
 Maumee Bay Beach Nowcast Results (2013).  

 

At Cuyahoga Valley National Park, nowcasts were provided to the public for 139 days during the recreational season of 2013. On 37 of these days, samples were taken to check nowcast results. The nowcast was able to provide more correct responses (89.1%) than the use of the previous day’s E. coli (77.8%) and both a higher sensitivity and specificity.
 Cuyahoga River Nowcast Results (2013).

At Villa Angela, nowcasts were provided to the public for 197 days during the recreational seasons of 2012-13. The nowcast was able to provide more correct responses (74.1%) than the use of the previous day’s E. coli (61.0%) and both a higher sensitivity and specificity.
 Villa Angela Beach Nowcast Results (2013).

For comments or changes regarding this Web page, please contact:
Donna Francy, USGS Ohio Water Science Center, 6480 Doubletree Avenue, Columbus, OH 43229; Phone: (614) 430-7769