Confederación Hidrográfica del Guadiana

Areas of Activity: Information Systems

Sectors of Operation: Irrigation Systems

 

 

In the last few years the Guadiana River Basin Authority has launched various lines of work with a range of initiatives linked to the deployment of information systems involving the utilization of geographic information to support some of the organization’s planning and management tasks.

In this context, geographic information on land cover is highly useful as an aid in the management of certain resources, especially water resources.

At the start of the project there were already various precedents in Spanish public bodies of remote sensing surveys based on satellite images for theme mapping of land cover and use. This work provided a proven methodological basis, supported by ongoing technological developments in the field of remote sensing, new satellite launches and improvements in satellite sensors, the possibilities shown by such techniques in application to land-use management and lower costs due to progress in the associated information technologies, for a series of assistance assignments by Adasa for the periodic generation of up-to-date agricultural theme maps and the establishment of a periodic service to ongoing updating.

The survey area is in the centre of Badajoz province (plus a small part of the south of Cáceres province), following a strip some 160 km long in an east-west direction, with the river Guadiana running along the middle, and covering the Vegas Altas and Vegas Bajas lowlands. The most typical irrigated crops grown in the area are maize, tomatoes and fruit trees, very widely planted in the four irrigable areas. In the Vegas Bajas area there are also notable quantities of winter cereals and beet, while in Vegas Altas large tracts are given over to rice.

The technical assistance provided by Adasa since 2005 has allowed the Guadiana River Basin Authority to be provided with a cartographic and image database for the irrigation seasons of 2005, 2006, 2007 and 2008, as well as a view of trends in the areas of the most widely planted crops in the irrigable regions and an estimate of the irrigated area, supplementing information from other sources.

The annual characterization of crops has been based on an analysis of satellite images taken on at least three dates in the year, followed by the usual central processing involved in this kind of work: quality control of images acquired, atmospheric and geometric corrections, identification of spectral signatures and supervised classification procedures with validation of results.

Each year’s processing work has been accompanied by intensive sampling in the field allowing us to identify, as confirmation on the ground, a large number of plots and the crop corresponding to each season. This sampling process has facilitated the identification of model plots for the generation of spectral signatures, as well as the very process of validating and estimating reliability in the identification of each crop in each irrigation season.

The results obtained (themed crop maps, satellite images and an associated database) have been integrated into the Basin Authority’s corporate geographic information system so that they may be displayed and accessed by all users with the necessary privileges.