Joost Wellens

Monitoring the evolution of irrigated areas with Landsat images using backward and forward change detection analysis in the Kou watershed

The Kou watershed is characterized by important water resources used for drinking, agriculture (especially in the irrigated areas), industry and the preservation of aquatic fauna and flora. For several decades, there has been increasing pressure on the Kous water resources, partly because of the expansion of the irrigated agricultural areas. This study was conducted to examine this issue, focusing on one specific irrigated area. In order to monitor the expansion of irrigated areas in developing countries, a low-cost remote sensing method based on Landsat images and aerial photographs was developed. The method is based on maximum-likelihood classification, followed by backward and forward change detection analysis requiring agronomic expertise. Using pixel trajectory analysis, the method connects all pixels to their consecutive states in order to correct their current states. The study showed that the irrigated area has expanded by almost 70% over 20 years, with most of this expansion occurring in the past 10 years. The method, if validated, could be used to obtain better information on past occupation in the rural irrigated areas for which there is currently no archived data, making temporal analyses impossible.

On the Use of Decision-Support Tools for Improved Irrigation Management: AquaCrop-Based Applications

Feeding more people with less water is putting efficient irrigation practices worldwide high on the agendas. As a reaction, over the last decades, numerous irrigation decisionsupport tools have been developed. For several reasons, the gap between farmer and modeler remained in most cases too large. The Food and Agriculture Organization of the United Nations (FAO) contributes to alleviate the encountered adoption limitations with AquaCrop and its stand-alone AquaCrop plug-in. This simple and robust fieldcrop-water balance has been successfully tested for a wide range of crops and regions, and its database is still expanding through worldwide contributions. The present chapter describes how AquaCrop can help irrigation advisory services draft efficient irrigation calendars that are easily applicable and adoptable: either by the elaboration of site-specific irrigation schedule calendars in chart format when the user has no access to the needed data or by the integration of its plug-in in a server/client ICT application offering centralized data management. As for the irrigation charts, studies prove 10-30% water savings, while maintaining yield and requiring minimum data. The server/client application offers an all-in advice tool, including real-time irrigation advice and yield forecasts. No adoption assessments have yet been carried out, but several ongoing pilot studies are promising.

Potato monitoring in Belgium with “WatchITGrow”

WatchITGrow is a web-based application developed for potato monitoring in Belgium. The different components encompass a back-end with biophysical parameters derived from high resolution satellite imagery, agrometeorological algorithms, phenological development and crop models; and a front-end with dashboards to visualize spatio-temporal information and insert potato field information.

Assessment of AquaCrop for winter wheat using satellite derived fCover data

The integration of crop growth models with remote sensing has presented great potential in (regional) crop yield forecasting; although so far few field-level applications exist. Based on crowd/farm-sourced observations (phenological stages and yield measurements) and a basic assimilation procedure using satellite (DMC) and digital hemispherical pictures (DHP) derived green fractional cover data (fCover), the AquaCrop plug-in model was assessed for winter wheat fields in Belgium. A semi-automated R-environment was developed to simultaneously run, assess and evaluate the ensemble of field-level simulations. The root mean square error (RMSE) was 0.8 ton/ha. It was concluded that the presented approach might be promising for large scale field-level yield forecasting.

Water conflicts in tropical watersheds: hydroeconomic simulations of water sharing policies between upstream small private irrigators and downstream large public irrigation schemes in Burkina Faso

A spatial hydroeconomic model was developed to analyze the competition between small private (SPIS) and large public (LPIS) irrigation systems for water control in tropical watersheds and applied to several water allocation policies in Kou watershed in Burkina Faso. Capital (cash and motorpumps) is the main constraining factor for SPIS expansion, and capital inflow accelerates SPIS development and reduces water flows for downstream LPIS users. As SPIS is more cost-effective and less water thirsty, LPIS needs to shift to less water-demanding and high-value crops or adopt more water-saving practices. Otherwise, only a sharp rice yield increase in LPIS can justify a reserved water quota for downstream users.