Soil Water dynamics and water balance on a coral island: Zhaoshu Island,
Studying soil water dynamics and water balance on coral islands is
important to utilize and manage the limited freshwater resources of
these islands. In this study, we investigated the soil water dynamics of
Zhaoshu Island, Xisha Archipelago, using observed data and the Richards
equation and analyzed the water balance of this island from October 2018
to September 2019. The precipitation, the water change values in the
entire flow domain (△Volume), the bottom boundary flux (vBot),
transpiration (Er), and evaporation (Es) during the entire observed year
were 913 mm, 10 mm, 349 mm, 203 mm, and 351 mm, respectively.
Precipitation is the only source of the freshwater, while approximately
38% of the precipitation infiltrated into the groundwater, 22% of the
precipitation was taken up by vegetation, and 39% of the precipitation
evaporated from the land surface. From November 2018 to April 2019 (dry
season), there was a dry soil layer at depths between 40 cm and 160 cm
in the soil profile. Evapotranspiration (ETa) was only 44 mm/month,
which was 94% greater than the amount of precipitation, and
approximately 14 mm/month of water was taken up from the groundwater by
plants. However, in wet season, infiltration dominated the processes of
soil water movement. Approximately 56% of the precipitation infiltrated
into the groundwater and 37% of the precipitation was consumed by ETa.
This study can help us to better understand the process of water
movement on coral islands and provide references for further management
to protect coral island ecology.