Mapping soil moisture with drones: challenges and opportunities

Droughts are increasing in frequency, magnitude and impact. Agroecosystems are anthropogenic ecosystems with high water demand, providing essential ecosystem services. Although water use efficiency has increased in agriculture in the last few decades, drought management should be based on long-term strategies for proactive water management, rather than crisis management. The AgrHyS network of sites in French Brittany collects high-resolution data on soil moisture across agronomic stations and catchments. Remote sensing has proven to be an excellent tool in upscaling point measurements up to catchment scale by using images captured by UAVs or satellites. Mapping soil moisture and plant water stress is crucial to perform water stress risk assessments. Our research seeks to upscale in situ point measurements of soil moisture and plant water stress not only in agricultural areas but also in natural ecosystems to assess the usability of UAV and satellite images in tracking and monitoring soil moisture. Our objectives are as follows: i) to demonstrate the applicability of UAVs in mapping soil moisture (SM) and plant water stress (PWS) by upscaling in situ measurements and to ii) evaluate the use of in situ measurements from a highly instrumented eLTER site in validating these essential water stress indicators.