Global Satellite-Based ET Products for the Local Level Irrigation Management: An Application of Irrigation Performance Assessment in the Sugarbelt of Swaziland

Abstract

Remote sensing techniques have been shown, in several studies, to be an extremely effective tool for assessing the performance of irrigated areas at various scales and diverse climatic regions across the world. Open access, ready-made, global ET products were utilized in this first-ever-countrywide irrigation performance assessment study. The study aimed at identifying ‘bright spots’, the highest performing sugarcane growers, and ‘hot spots’, or low performing sugarcane growers. Four remote sensing-derived irrigation performance indicators were applied to over 302 sugarcane growers; equity, adequacy, reliability and crop water productivity. The growers were segmented according to: (i) land holding size or grower scale (ii) management regime, (iii) location of the irrigation schemes and (iv) irrigation method. Five growing seasons, from June 2005 to October 2009, were investigated. The results show while the equity of water distribution is high across all management regimes and locations, adequacy and reliability of water needs improvement in several locations. Given the fact that, in general, water supply was not constrained during the study period, the observed issues with adequacy and reliability of irrigation in some of the schemes were mostly due to poor scheme and farm level water management practices. Sugarcane crop water productivity showed the highest variation among all the indicators, with Estate managed schemes having the highest CWP at 1.57 kg/m3 and the individual growers recording the lowest CWP at 1.14 kg/m3, nearly 30% less. Similarly center pivot systems showed to have the highest CWP at 1.63 kg/m3, which was 30% higher than the CWP in furrow systems. This study showcases the applicability of publicly available global remote sensing products for assessing performance of the irrigated crops at the local level in several aspects.

A Framework for Irrigation Performance Assessment Using WaPOR data: The case of a Sugarcane Estate in Mozambique

“…A CV of 0 to 10 % is defined as good equity, CV of 10 to 25 % as fair equity and CV > 25 % as poor equity (Bastiaanssen et al, 1996;Karimi et al, 2019).…”

“…the ratio of seasonal ETa over seasonal potential evapotranspiration (ETp,s) (Kharrou et al, 2013;Karimi et al, 2019). The seasonal ETp,s is aggregated from the monthly value of crop coefficient of sugarcane (Table A2) times the reference evapotranspiration (Allen et al, 1998).…”

“…The seasonal ETp,s is aggregated from the monthly value of crop coefficient of sugarcane (Table A2) times the reference evapotranspiration (Allen et al, 1998). Good adequacy performance is defined for the range of 0.8<A<=1, acceptable range 0.68<A<=0.8 and poor performance A <=0.68 (Karimi et al 2019).…”

Influence of Spatial Resolution on Remote Sensing-Based Irrigation Performance Assessment Using WaPOR Data

“…The use of remote sensing to estimate and evaluate various indicators for irrigation performance at the irrigation scheme level (i.e., the irrigation perimeter) has been tested and reported for multiple spatial and temporal resolutions (e.g., spatial resolution refers to the pixel size, and temporal resolution refers to the satellite revisit time). These include studies on indicators including equity [2,6,12], adequacy [6,13,14], sustainability [2,13], and water productivity [15][16][17]. These studies used datasets with input sensors of varying resolution, including Landsat TM with a resolution of 30 m and 16-day revisit and moderate resolution imaging spectroradiometer (MODIS) Terra with resolutions of 250 m and 1-day revisit or 500 m and 8-day revisit.…”

Use of Remote Sensing and Geographic Information Systems in Irrigation Performance: A Case Study of Atabey Irrigation Scheme

“…In irrigated agriculture, however, they are used in the studies of daily or seasonal evapotranspiration, crop stress, irrigation monitoring and management, determination of the water content of field crops, water resources mapping, and salinity. By using these systems, the performances of irrigation schemes were determined in India by Thiruvengadachari and Sakthivadivel (1997), in Brazil by Bastieansen et al (2000), in Niger by Zwart et al (2010), in Córdoba, Spain by Santos et al (2010), in Egypt by Elnmer et al (2018), in California by Taghvaeian et al (2018), and in Swaziland by Karimi et al (2019).…”