Development and applications of a new database of soil physical properties for the Kansas Mesonet

Abstract

In this dissertation, we investigated three central questions to improve mesoscale soil moisture monitoring using the Kansas Mesonet. Our first question was: i) Can we improve the accuracy of soil moisture measurements and related soil water processes by characterizing site-specific soil physical properties? We developed a comprehensive database of site- and depth-specific soil physical properties for the Kansas Mesonet. We analyzed a total of 320 soil samples collected from four sensor depths at 40 stations of the Kansas Mesonet monitoring soil moisture and soil temperature. The resulting database comprises 14 site and depth-specific soil hydraulic properties and three soil thermal properties for 40 stations of the Kansas Mesonet. In addition, the database of soil physical properties allowed us to identify an improved calibration model for the soil moisture sensors used by the Kansas Mesonet. Our second question was: ii) Can we re-construct precipitation events using changes in rootzone soil water storage to improve operational quality control and quality assurance of precipitation observations in mesoscale networks? Co-located hourly soil moisture and precipitation observations from May 2017 to December 2020 at 30 Kansas Mesonet stations were analyzed to test whether the rootzone can be used as a natural rain gauge. Precipitation events were back-calculated from soil moisture as the sum of hourly differences in profile soil water storage. The proposed soil moisture approach correctly flagged 82% of the precipitation events. Precipitation amounts and timing obtained from in situ soil moisture were more accurate than using precipitation observations from the nearest station when the nearest neighbor station was at a distance of >15 km. Our third question was: iii) Are traditional and modern laboratory methods for measuring soil water retention curves compatible? We compared water retention curves developed for a total of 24 soil samples from five different textural classes using traditional instrumentation (tension tables, pressure cells, and pressure plate) and modern instrumentation (precision tensiometers and a dew point water potential meter). Both traditional and modern methods resulted in similar water contents at saturation, field capacity, and permanent wilting point, but the traditional method had residual water content 125% higher than modern methods.