Puerto Rico StreamStats

StreamStats basin characteristics functionality became available for Puerto Rico in April 2021. It allows the user to delineate the drainage basin from a selected point and generate values of the following basin characteristics:

• Perimeter of the drainage basin, in miles;
• Mean basin slope computed from 10 m DEM;
• Change in elevation between points 10 and 85 percent of length along main channel to basin divide divided by length between points, in feet per mile;
• Drainage area, in square miles;
• Mean basin elevation, in feet;
• Mean annual reference evapotranspiration from Penman Montieth method, in millimeters;
• Maximum 24-hour precipitation that occurs on average once in 5 years, in inches;
• Average percentage of impervious land cover from NLCD 2001;
• Length of longest flow path, in miles;
• Minimum basin elevation, in feet;
• Mean annual precipitation, in inches;
• Minimum depth to bedrock, in inches;
• Percentage of area of Hydrologic Soil Type B from SSURGO.

Click on this link to obtain general information on the Puerto Rico application, as well as specific sources and computation methods for basin characteristics. 

Low-flow and flow duration functionality were implemented on July 9, 2021. These flow scenarios allow 1-, 7-, 14-, and 30-day mean low-flows at 50-, 20-, and 10- percent chance exceedance levels; and flow durations for the 99-, 98-, 95-, 90-, 80-, 70-, 60-, and 50- percent exceedance probabilities to be estimated for delineated basins. Warning: Users are cautioned to thoroughly check low flow and duration flow estimates for instances of "crossing," where flows do not increase or decrease as expected. If crossing is found to occur in StreamStats output, a graphical adjustment should be applied. Details regarding development of the low flow and duration flow regression equations can be found in the source report:

• Williams-Sether, T., 2021, Estimating flow-duration statistics and low-flow frequencies for selected streams and the implementation of a StreamStats web-based tool in Puerto Rico: U.S. Geological Survey Scientific Investigations Report 2021–5054 Version 2, 18 p.

Flood frequency regression equations have been developed and are currently undergoing implementation. Once implemented, the flood frequency scenario will allow peak flows at 50-, 20-, 10-, 4-, 2-, 1-, 0.5-, and 0.2-percent chance annual exceedance levels to be estimated for delineated basins.