Water Wheel March/April 2025: Remote Sensing

Abstract

Surface soil moisture is an essential climate variable (ECV; moisture) which is monitored to inform our understanding of changes in the atmosphere and earth. Soil moisture is also an important indicator, in addition to vegetation and soil types, of the presence of a wetland. According to the South African National Water Act, Act 36 of 1998 (RSA, 1998:18), wetlands are defined as ‘land which is transitional between terrestrial and aquatic systems where the water table is usually at or near the surface, or the land is periodically covered with shallow water, and which land in normal circumstances supports or would support vegetation typically adapted to life in saturated soil’ . Only the top 50 cm of soil is used for wetland identification and delineation (DWAF, 2005). Therefore, to be able to detect a wetland using soil moisture as an indicator, we should be able to detect and monitor changes in soil moisture up to 50 cm of depth. In South Africa, wetlands make up < 7% of the extent of the land mass, however, we have not detected all our wetlands yet (Van Deventer et al., 2020).

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