CROP DATA RETRIEVAL USING EARTH OBSERVATION DATA TO SUPPORT AGRICULTURAL WATER MANAGEMENT

Irrigation water requirements (IWR) estimation requires the availability of accurate crop data, which can be acquired, along the crop growth season for a given region, through the use of Earth Observation (EO) time series. Besides, a relationship between the crop´s coefficients and the normalized difference vegetation index (NDVI) can be established allowing the crop´s evapotranspiration estimation. The main objective of the present work is to develop a methodology, and its implementation in a computational application, to extract crop’s parameters from EO images time series for a set of parcels of different types of crops, to be used as input data for a soil water balance model to compute IWR. The methodology was tested in two distinct test sites, Vila Franca de Xira (site I) and Vila Velha de Rodao (site II) municipalities, Portugal. Landsat 7 and 8 images acquired from April to October 2013 were used for site I, while SPOT-5 Take-5 images from April to September 2015 were considered for site II. EO data was used to estimate the basal crop’s coefficients, the planting dates and the lengths of crop’s growth stages. Based on crop, soil and meteorological data, IWR for the main crops of both test regions were estimated using the IrrigRotation model. The crop coefficients values obtained from EO data proved to be reliable for the IWR estimation.