Reconstructing Precipitation Events Using Collocated Soil Moisture Information

Complete and accurate precipitation records are important for developing reliable flood warning systems, streamflow forecasts, rainfall-runoff estimates, and numerical land surface predictions. Existing methods for flagging missing precipitation events and filling gaps in the precipitation record typically rely on precipitation from neighboring stations. In this study, we investigated an alternative method for back-calculating precipitation events using changes in root-zone soil water storage. Our hypothesis was that using a different variable (i.e., soil moisture) from the same monitoring station will be more accurate in estimating hourly precipitation than using the same variable (i.e., precipitation) from the nearest neighboring station. Precipitation events were estimated from soil moisture as the sum of hourly changes in profile soil water storage. Hourly precipitation and soil moisture observations were obtained from a mesoscale network in the central U.S. Great Plains from May 2017 to December 2020. The proposed method based on soil moisture had a minimum detectable limit of 7.6 mm (95th percentile of undetected precipitation events) due to canopy and soil interception. The method was outperformed by the nearest neighbor (NN) interpolation method when neighboring stations were at distances of <10 km. However, the proposed method outperformed the NN method in 22 out of 27 stations when nearest stations were at distances > 10 km. Using changes in soil water storage was an effective approach for flagging and estimating actual missing precipitation events caused by pluviometer malfunction, highlighting new opportunities for using readily available in situ soil moisture information for operational quality control of precipitation observations in mesoscale environmental monitoring networks. Significance Statement: This study investigated a new method for reconstructing precipitation events using changes in root-zone soil water storage. The method consists of a new option for improving the quality control of precipitation observations collected at in situ environmental monitoring networks. Using the sum of hourly changes in soil water storage proved effective as a qualitative method for flagging missing precipitation events caused by pluviometer failure and as a quantitative method for reconstructing precipitation events. This study presents a promising application of in situ soil moisture information as an alternative method for quality control of precipitation and as a method for filling gaps in the historical precipitation record of catchment-scale hydrological networks and mesoscale environmental monitoring networks.