Submitted to: Water Resources Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/27/2007
Publication Date: 5/16/2008
Citation: Keefer, T.O., Unkrich, C.L., Smith, J.R., Goodrich, D.C., Moran, M.S., Simanton, J.R. 2008. An event-based comparison of two types of automated-recording, weighing bucket rain gauges. Water Resources Research, Vol. 44, W05S12, doi:10.1029/2006WR005841. Interpretive Summary: An improved electronic type of recording raingage was installed at Walnut Gulch Experimental Watershed replacing the mechanical type that has been in operation there for the past 50 years. From 2000 through 2004 the electronic and mechanical types of raingages were operated side-by-side so that an exhaustive analysis of the comparable measurements could be undertaken. The results showed 1) that there is virtually no difference between individual electronic raingages, 2) the data processing procedures of the mechanical raingage may introduce errors affecting the measured peak rainfall intensity but only at short time intervals of less than 5 minutes, 3) the electronic and mechanical raingages are equivalent for most measures of rainfall such as depth and intensity measured over time intervals of 5 minutes or more, and 4) computer simulations of runoff will only be affected in limited cases on very small watershed areas, less than 1 acre.
Technical Abstract: A multi-year, multi-gage comparison of two types of automated-recording weighing-bucket raingages was conducted using precipitation data collected at the United States Department of Agriculture, Agricultural Research Service’s Walnut Gulch Experimental Watershed in Southeast Arizona. The comparison was part of the conversion of all raingages on the watershed from an analog-recording mechanical-weighing raingage to a datalogger controlled digital-recording electronic-weighing raingage with radio telemetry. This comparison applied to nine pairs of analog and digital raingages that were in co-incident operation during a five-year period, January 1, 2000 to December 31, 2004. This study showed that 1) individual digital raingages recorded precipitation equivalently; 2) high errors in event intensities may be produced when analog charts are digitized at short time intervals; 3) for several different measures of precipitation, the analog and digital data were equivalent; and 4) implications for the rainfall-runoff model, KINEROS2, showed a limited but significant effect in modeled runoff due to differences in analog and digital raingage input precipitation intensities. This study provided a useful analysis for long-term raingage networks that have recently converted, or will soon convert, from analog to digital technology. Understanding these differences and similarities will benefit interpretation of the ultimately combined long-term precipitation record and provide insights into the impacts on hydrologic modeling.