Topographic Wetness Index as a Proxy for Soil Moisture in a Hillslope Catena: Flow Algorithms and Map Generalization

Hans Edwin Winzeler (), Phillip R. Owens, Quentin D. Read, Zamir Libohova, Amanda Ashworth and Tom Sauer
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Hans Edwin Winzeler: USDA ARS, Dale Bumpers Small Farms Research Center, 6883 AR-23, Booneville, AR 72927, USA
Phillip R. Owens: USDA ARS, Dale Bumpers Small Farms Research Center, 6883 AR-23, Booneville, AR 72927, USA
Quentin D. Read: USDA ARS, Southeast Area, 3127 Ligon St., Raleigh, NC 27607, USA
Zamir Libohova: USDA ARS, Dale Bumpers Small Farms Research Center, 6883 AR-23, Booneville, AR 72927, USA
Amanda Ashworth: USDA-ARS, Poultry Production and Product Safety Research Unit, 1260 W. Maple St., Fayetteville, AR 72701, USA
Tom Sauer: USDA ARS, National Laboratory for Agriculture and the Environment, 1015 N. University Boulevard, Ames, IA 50011, USA

Land, 2022, vol. 11, issue 11, 1-23

Abstract: Topographic wetness index (TWI) is used as a proxy for soil moisture, but how well it performs across varying timescales and methods of calculation is not well understood. To assess the effectiveness of TWI, we examined spatial correlations between in situ soil volumetric water content (VWC) and TWI values over 5 years in soils at 42 locations in an agroforestry catena in Fayetteville, Arkansas, USA. We calculated TWI 546 ways using different flow algorithms and digital elevation model (DEM) preparations. We found that most TWI algorithms performed poorly on DEMs that were not first filtered or resampled, but DEM filtration and resampling (collectively called generalization) greatly improved the TWI performance. Seasonal variation of soil moisture influenced TWI performance which was best when conditions were not saturated and not dry. Pearson correlation coefficients between TWI and grand mean VWC for the 5-year measurement period ranged from 0.18 to 0.64 on generalized DEMs and 0.15 to 0.59 for on DEMs that were not generalized. These results aid management of crop fields with variable moisture characteristics.

Keywords: topographic wetness index; compound topographic index; soil moisture; soil moisture regimes; SAGA wetness index; volumetric water content; flow algorithms; DEM filtration; DEM resampling; seasonal soil moisture (search for similar items in EconPapers)
JEL-codes: Q15 Q2 Q24 Q28 Q5 R14 R52 (search for similar items in EconPapers)
Date: 2022
References: View complete reference list from CitEc
Citations: View citations in EconPapers (3)

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