Uncharted territory: Mapping diverse and dispersed smallholder irrigation in Sub-Saharan Africa through remote sensing

In recent years, there has been a renewed interest in irrigation in sub-Saharan Africa (SSA) due to the need for agricultural development and food security. Expanding irrigation is necessary to meet the region’s food requirements with the projected population growth. Smallholder farmers have long been driving irrigated agriculture in SSA for a long time through farmer-led irrigation development (FLID). Farmers have independently initiated, operated, and maintained irrigation infrastructure, often focusing on high-value cash crops to improve their income. However, FLID often goes unnoticed by official institutions due to its fragmented nature and the technical bias in defining irrigation. The small scale and heterogeneity of FLID make it challenging to accurately count and report official statistics. Moreover, the practices of smallholder farmers are sometimes considered inferior or irrelevant compared to “modern” irrigation technologies.Similar challenges arise when mapping with remote sensing (RS) due to the complex and diverse nature of these systems. Several factors contribute to the difficulty in accurately measuring and classifying irrigated agriculture using satellite sensors. These factors include the similarity in spectral signatures between different land cover classes, mixed spectral signatures within the same land cover class, complex shapes and arrangements of fields, and subjective definitions of irrigation.Despite these challenges, RS offers several advantages for mapping irrigated agriculture. It provides wide spatial coverage, allows monitoring of temporal and spatial trends, and assists in prioritizing field visits. RS data can be consistently analysed over time and is easily accessible. Different classes of irrigated agriculture can be distinguished by considering factors such as the timing of image acquisition, variations in vegetation colour, and notable changes.This thesis aims to examine the production of remote sensing maps and their ability to depict irrigated agriculture. While remote sensing cannot directly measure farmer-led irrigation, it can capture the diverse and dispersed nature of small-scale irrigated agriculture, which requires interpretation through fieldwork and local expertise. The research identifies and addresses potential challenges in mapping irrigated agriculture in SSA using remote sensing data.The research uses four case studies in Mozambique, specifically Chokwe, Xai-Xai, Manica, and Catandica, chosen for their diverse agroecological characteristics and the presence of both small-scale and large-scale irrigated agriculture.