NSS Known Issues as of 2016/04/25

TABLE OF CONTENTS

General program issues
Arizona
Colorado
Georgia
Iowa
Massachusetts
New Mexico
North Carolina
Rhode Island
South Carolina
Texas
Utah

General program issues

Prediction Intervals computed for some equations in NSS will display the wrong values when metric display is selected from the NSS Options menu. Do NOT use the metric display option until further notice.

Bank-full equations computed by NSS will only compute correctly in Imperial units. Switching to metric units will cause many of these to compute incorrectly.

Arizona

Equations using slope variables from SIR 2006-5306 incorrectly requested slope values in units of percent when NSS was using version of the database prior to 2016-04-25. Parameters should be entered as unitless (ft per ft) as now requested by NSS.

Colorado

If input variables include "Percent_above_7500_ft", enter actual percentage (not percentage plus 1 as indicated in the associated report number SIR 2009_5136). The one will be added by NSS during its computations. Also note that prediction errors for Annual Monthly and Mean Streamflows have been corrected for Mountain, Northwest, Rio Grande, and Southwest hydrologic regions as well as Duration flows for Southwest hydrologic region.

Equations using slope variables from SIR 2006-5306 incorrectly requested slope values in units of percent when NSS was using version of the database prior to 2016-04-25. Parameters should be entered as unitless (ft per ft) as now requested by NSS.

Georgia

For Peak_Southeast_US equations in Georgia, North Carolina, or South Carolina, the sum of all percentages entered into NSS by the user must be equal to 100% in order for the equation output to be valid. If all output values report zero, the rounded sum of input values did not equal 100%. Since NSS rounds to 3 significant figures, it is best to enter only 3 significant figures and make sure that all rounded parameters add to 100%. See report number SIR 2009-5043 (GA), SIR 2009-5158 (NC), or SIR 2009-5156 (SC) for further details. Links to these reports can be found on the NSS publications page at: http://water.usgs.gov/osw/programs/nss/pubs.html

Note: NSS results from databases starting with the 2014-03-26 version and ending before the 2014-10-07 version may have produced incorrect results if the above input rule was violated. Results from inputs that added to 100% were unaffected by this error.

Iowa

Equation results for M1D10Y, M7D10Y, M1D10Y1012, and QAH from Low_Flow_Southern_Region_2012_5171 computed incorrectly when using NSS databases dated earlier than 2015-09-29. Users should recompute using a newer version.

Massachusetts

The Massachusetts-Rhode Island Water Science Center strongly recommends contacting a hydrologist from their office before using any peak flow estimates generated by NSS for Massachusetts.

New Mexico

Equations using slope variables from WRIR 01-4271, SIR 2008-5119, and SIR 2006-5306 incorrectly requested slope values in units of percent when NSS was using version of the database prior to 2016-04-20. Parameters should be entered as unitless (ft per ft) as now requested by NSS.

North Carolina

For Peak_Southeast_US equations in Georgia, North Carolina, or South Carolina, the sum of all percentages entered into NSS by the user must be equal to 100% in order for the equation output to be valid. If all output values report zero, the rounded sum of input values did not equal 100%. Since NSS rounds to 3 significant figures, it is best to enter only 3 significant figures and make sure that all rounded parameters add to 100%. See report number SIR 2009-5043 (GA), SIR 2009-5158 (NC), or SIR 2009-5156 (SC) for further details. Links to these reports can be found on the NSS publications page at: http://water.usgs.gov/osw/programs/nss/pubs.html

Note: NSS results from databases starting with the 2014-03-26 version and ending before the 2014-10-07 version may have produced incorrect results if the above input rule was violated. Results from inputs that added to 100% were unaffected by this error.

Rhode Island

Prior to the 2015-06-12 version of the database, Rhode Island peak-flow equations from SIR 2012-5109 produced slightly different results when weighting an ungaged location with a gaged location, due to the use of wrong drainage area exponents in previous versions. Errors were on the order of 1%.

South Carolina

For Peak_Southeast_US equations in Georgia, North Carolina, or South Carolina, the sum of all percentages entered into NSS by the user must be equal to 100% in order for the equation output to be valid. If all output values report zero, the rounded sum of input values did not equal 100%. Since NSS rounds to 3 significant figures, it is best to enter only 3 significant figures and make sure that all rounded parameters add to 100%. See report number SIR 2009-5043 (GA), SIR 2009-5158 (NC), or SIR 2009-5156 (SC) for further details. Links to these reports can be found on the NSS publications page at: http://water.usgs.gov/osw/programs/nss/pubs.html

Note: NSS results from databases starting with the 2014-03-26 version and ending before the 2014-10-07 version may have produced incorrect results if the above input rule was violated. Results from inputs that added to 100% were unaffected by this error.

Texas

Users needing to estimate peak streamflows for Texas should consult report number SIR 2009-5087 before using NSS to solve the regional regression equations. This report provides information needed by the user to determine input values and application limits. Failure to do so may result in improper estimates. This report replaces previous peak-flow equations from WRIR 96-4307.

Utah

Equations using slope variables from SIR 2006-5306 incorrectly requested slope values in units of percent when NSS was using version of the database prior to 2016-04-25. Parameters should be entered as unitless (ft per ft) as now requested by NSS.