Geographia Technica, Vol 19, Issue 1, 2024, pp. 89-102
CORRELATIONS BETWEEN TOPOGRAPHIC WETNESS INDEX AND SOIL MOISTURE IN THE PANNONIAN REGION OF CROATIA
Hrvoje HEŠTERA 
, Mladen PLANTAK , Dalibor GERNHARDT
ABSTRACT: The study investigates the relationship between variations of topographic wetness indices, resampled digital elevation model (DEM) resolutions and soil moisture in Croatia’s Pannonian region during all seasons. It delves into the spatial distribution of soil moisture, vital for various sectors including agriculture, forestry, ecology, and military. Utilizing topographic wetness index (TWI), the research focuses on resampling high-resolution DEM into coarser resolutions and flow-routing methods concerning in-situ soil moisture measurements. It encompasses the Kaznica River catchment area, characterized by diverse topography and soil types, including fine-grained automorphic and hydromorphic clays. The study extensively conducts field measurements, evaluating soil moisture at various depths (1, 15, 30, and 45cm) across all seasons, cross-referenced with meteorological data. Through an examination of six runoff algorithms and six spatial resolutions, it concludes that the optimal TWI resolution for correlation with soil moisture is 150m at a 30cm soil depth. However, it stresses the necessity of calibrations for precise soil depth, cell resolutions and season. The shallowest soil depth has the lowest correlation coefficients in all periods, while the highest coefficients were achieved in period with the highest soil moisture values. Recognizing the complexity of factors influencing soil moisture, it recommends the integration of additional data sources like remote sensing, other geomorphological indexes, and detailed land cover analysis to enhance the accuracy of predictions.
Keywords: Topographic Wetness Index, Soil wetness, Loess, Digital Elevation Model, Raster cell resolution
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