Uncertainty in Rainfall Measurements and Its Implications to Hydrologic Modeling.

Measurements from tipping bucket rain gauges (TBRs) consist of systematic and random errors as an effect of external factors, such as mechanical limitations, wind effects, evaporation losses, and rainfall intensity. Three different models of tipping bucket rain gauges (TBRs), viz. HS-TB3 (Hydrological Services Pty Ltd.), ISCO-674 (Isco, Inc.) and TR-525 (Texas Electronics, Inc.), were calibrated in the lab to quantify measurement errors across a range of rainfall intensities (5 mm·h− 1 to 250 mm·h− 1) and three different volumetric settings. All three TBR models showed a substantial deviation (α = 0.05) in measurements from actual rainfall depths, with increasing underestimation errors at greater rainfall intensities. Correction equations were developed and applied to field-collected rainfall data. Sensitivity and performance of hydrologic models, viz. SWAT and DRAINMOD were assessed using the uncorrected versus corrected rainfall data for a sub-watershed of Upper Big Walnut Creek Watershed in Ohio. The results of this study will be presented.