Monitoring the groundwater level in tropical peatland through UAV mapping of soil surface temperature: a pilot study in Tanjung Leban, Indonesia

There is increasing interest in the use of unmanned aerial vehicles (UAVs) as cost-effective, high-resolution alternatives to satellites for the environmental monitoring of large areas. In this study, we tested the feasibility of using UAV-acquired soil surface temperature to monitor groundwater level in a peatland undergoing groundwater restoration to mitigate fire risk (Tanjung Leban, Indonesia). We used two UAVs (Inspire 1, with an infrared camera, and Phantom 4) to map soil surface temperatures at 459 points on bare land. Using a spline analysis of groundwater-level and elevation data in Arc GIS 10.6, we produced ground elevation and groundwater table maps and measured the groundwater level (depth from the ground surface) at each bare-land point. Spearman's rank correlation analysis determined a negative correlation between the soil surface temperature and groundwater level. Our study shows that soil surface temperature is a reliable proxy for groundwater level in tropical peatlands. This proxy can be monitored cost-effectively using UAVs equipped with infrared cameras.