Soil water dynamics and water balance on a tropical coral island. Issue 12 (14th December 2021)

• Record Type: Journal Article
• Authors: Han, Shengsheng; Liu, Suxia; Mo, Xingguo; Yang, Lihu; Song, Xianfang
• Is Part Of: Hydrological processes. Volume 35:Issue 12(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-12-14
• Subjects: evaporation -- groundwater‐dependent ecosystem -- Hydrus‐1D -- root water uptake -- transpiration -- Zhaoshu Island; Hydrology -- Periodicals; Hydrology -- Research -- Periodicals; Hydrologic models -- Periodicals; Hydrological forecasting -- Periodicals; 631.432
• DOI: 10.1002/hyp.14415
• Languages: English
• ISSNs: 0885-6087

Abstract

Abstract: Understanding soil water dynamics and the water balance of tropical coral islands is important for the utilization and management of their limited freshwater resources, which is only from rainfall. However, there is a significant knowledge gap in the influence of soil water on the water cycle of coral islands. Soil water dynamics and the water balance of Zhaoshu Island, Xisha Archipelago were thus investigated using soil moisture measurements and the Hydrus‐1D model from October 2018 to September 2019. Over the study period, vegetation transpiration, soil evaporation, groundwater recharge and storage in the vadose zone were approximately 196, 330, 365 and 20 mm, occupying 22%, 36%, 40% and 2% of annual rainfall total (911 mm), respectively. For the wet season (from May to October) these values became 75, 202, 455 and 40 mm, occupying 10%, 26% and 59% and 5% of the seasonal rainfall total (772 mm), respectively. During the dry season (from November to April), a dry soil layer between 40 and 120 cm depth of the soil profile was identified that prevented water exchange between the upper soil layers and the groundwater resulting in the development of deep roots so that vegetation could extract groundwater to supplement their water requirements. Vegetation not only consumes all dry season rainfall (140 mm) but extracts water deeply from groundwater (90 mm) as well as from the vadose layer (20 mm). As such, the vegetation appears to be groundwater‐dependent ecosystems. The research results aid us to better understand the process of water dynamics on coral islands and to protect coral island ecosystems. Abstract : The rainfall, Δvolume, bottom boundary flux, transpiration and evaporation were 911, 20, 365, 196 and 330 mm, respectively from October 2018 to September 2019. A dry soil layer was found at depths between 40 and 120 cm from November 2018 to May 2019 (dry season). In the dry season, evapotranspiration was 42 mm −1 month, of which 19 mm −1 month was extracted from groundwater by plants. Vegetation on the coral islands use shallow soil water preferentially in the wet season and switch to deeper soil layers as shallow layers become dry.