Spatial variability assessment of irrigation performance in the Lower Usuthu Smallholder Irrigation Project (LUSIP) in Eswatini

Abstract

The performance of most smallholder sugarcane growers in Eswatini has been underwhelming and this has been largely attributed to inefficient irrigation systems. As such, the Government of Eswatini has made huge irrigation investments towards smallholder farming with the intention of advancing access to water and consequently, improve irrigation efficiency. There is, however, a lack of evidence to support such an assumption hence the need for this study which was conducted at the LUSIP area in Eswatini. The main objective was to assess the irrigation performance of schemes under LUSIP area over three cropping seasons using remote sensing-derived indicators. More specifically, the objective was to determine the spatiotemporal variability for adequacy, equity, reliability and water productivity using the python module for Surface Energy Balance Algorithm for Land (PySEBAL). Results showed that relative evapotranspiration $\left({ET}_{\mathrm{rel}}\right)$ was 0.86, 0.88 and 0.82 for the 2013/14, 2014/15 and 2015/16 seasons, respectively. The seasonal coefficient of variation of ${ET}_{\mathrm{rel}}$ was 0.05, 0.07 and 0.06 for 2013/14, 2014/15 and 2015/16, respectively. All results indicated that performance indicators were within allowable limits except for water productivity. Water productivity decreased with each passing season and in 2014/15 and 2015/16 water productivity values (1.29 and 1.09 kg/m³) were below the acceptable range of 1.3–2.2 kg/m³. It was, therefore, concluded that on average, irrigation performance in the area was within allowable ranges. It was, however, recommended that in the future yield and its associated factors be investigated. Such studies could inform strategies that can be used to improve water productivity.