Application of Geospatial techniques in assessing supplemental Irrigation for sorghum and maize production in Karamoja Region

Abstract

Karamoja region is situated in north-eastern Uganda. Over 80% of the population in this region is moderately food insecure, and this has oftenly prompted relief agencies to engage in humantarian relief especially food aids for atleast the last three decades. The main objective of this study was to apply geospatial techniques in determining supplemental irrigation requirements for Maize and Sorghum production in this region. To achieve this goal, a land suitability analysis employing the use of spatial Multi-Criteria Evaluation (SMCE) tool in Integrated Land and Water Information System (ILWIS) was carried out. This involved the development of relevant geospatial datasets for the study area. The generated datasets were structured, standardized and weighted in ILWIS, from which the respective suitability maps for Maize and Sorghum production were calculated. The SMCE results showed 85.3% and 45.4% of the area in the region as being at least moderately suitable for Maize and Sorghum production, respectively. An irrigation suitability analysis was then conducted by initially establishing the average decadal effective rainfall maps for each of the designed three (3) seasons across the set scenarios i.e. wet, normal and dry scenarios. Average decadal net irrigation requirement (NIR) maps, as a deficit of the respective calculated average decadal crop water requirements and the effective rainfall maps earlier developed, were then determined and classified using set NIR ranges and logical-IFF condition commands in ILWIS. Finally cropping and irrigation alternatives to guide effective land utilization were determined following an inferential approach in which statistic information summarizing specific acreages and percentages at varying suitability index for each crop across all scenarios was collated. It was observed for Season-1 (running from March to June) that significant areas are highly suitable for both crops particularly in the wet year scenario. This is majorly attributed to the relatively higher effective rainfalls in the region around this time of the year, thus eliminating the need for irrigation. Season-2 (running from July to October) showed significant areas falling in the marginally suitable class. The region was particularly observed to have up to 57% of the area marginally suitable for Sorghum production in the dry year scenario. The increase in marginal suitability is majorly attributed to the relatively high NIR during this season. Season-3 which runs from November to February coincides with the driest spell in this region with average decadal rainfall ranging from 0-26 mm as compared to the 10-54 mm in Season-1. This statistic calls for relatively more irrigation water supply across all three scenarios of Season-3 in order to guarantee effective crop production. The results of this study show the extent of supplemental irrigation required to sustain effective crop production in the various areas of Karamoja region. The study recommends that a more detailed soil water balance analysis, at a relatively higher spatial resolution be conducted in the future in order to ascertain the specific contribution of other ambient factors to supplemental irrigation estimation within the study area.