Jean-Louis Janeau (IRD-iEES Paris) and Nitjaporn Koonklang (IRD assistant) were in the field during the first week of May to survey the land use in Huay Ma Nay catchment, Phrae Province, Thailand. They described the soil surface features of more than 300 measurement points in this hilly catchment with steep slopes, mostly covered by maize crop. Field measurements will allow calibrating and validating the observations processed from satellite images. Such field surveys are done every year since 2016 to get the annual land use map that will be further refined at the GET laboratory in Toulouse.
These maps are necessary to understand the hydro-sedimentary balances in this watershed, which is representative of the steep agricultural areas of northern Thailand. Annual burning from farmer to eliminate parasites, grass and crop residues, lead to high erosion of bare soils at the beginning of the rainy season.