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

ABSTRACT Accurate crop data are essential for reliable irrigation water requirements (IWR) calculations, which can be acquired during the crop growth season for a given region using earth observation (EO) satellite time series. In addition, a relationship between crop coefficients and the NDVI can be established to allow for crop evapotranspiration estimation. The main objective of the present work was to develop a methodology, and its implementation in an application software, to extract crop parameters from EO image 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 at two distinct test sites, the Vila Franca de Xira (site I) and Vila Velha de Ródão (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 were used to estimate the basal crop coefficients, planting dates, and crops growth stage lengths. Based on crop, soil and meteorological data, the IWR for the main crops of both test regions were estimated using the IrrigRotation model. The crop coefficient curves obtained from the EO data proved to be reliable for IWR estimation.

摘要
准确的作物数据是可靠计算灌溉需水量（IWR）的核心前提，此类数据可通过地球观测（EO）卫星时序影像，在特定区域的作物生长季内获取。此外，可建立作物系数与归一化植被指数（NDVI）之间的关联关系，以此实现作物蒸散量的估算。本研究的核心目标为开发一套方法学体系，并将其集成至应用软件中，以从多类作物地块的EO影像时序数据中提取作物参数，将其作为土壤水量平衡模型的输入数据，用于计算灌溉需水量。该方法在葡萄牙的两个市镇试点区域——维拉弗兰卡迪谢拉（试点I）与罗德昂新镇（试点II）——开展了测试验证：试点I采用2013年4月至10月期间获取的Landsat-7与Landsat-8影像，试点II则采用2015年4月至9月期间获取的SPOT-5 Take-5影像。研究利用EO数据估算了基础作物系数、播种日期以及作物生育期时长；结合作物、土壤与气象数据，采用IrrigRotation模型对两个试点区域的主要作物灌溉需水量进行了估算。经验证，基于EO数据获取的作物系数曲线可有效用于灌溉需水量估算。