Climate suitability analysis of alternate wetting and drying irrigation for expansion of rice cultivation in Uganda :

Abstract

Rice cultivation plays a significant role in contributing to food security in Uganda. Paddy cultivation is carried out using traditional continuous flooding practice that requires a lot of water, contributes to greenhouse gas emissions, posing a threat to the future of paddy production due to climatic changes causing droughts and water scarcity. Promotion of sustainable water management practices such as alternate wetting and drying (AWD) irrigation is required. This study investigated the suitability of AWD irrigation as a climate-smart water management technique to improve on water management in paddy rice fields in Uganda. Relevant climate data, including temperature, precipitation, evapotranspiration, and soil moisture, were used to analyze the current and future climate suitability of the technique in paddy rice fields. The data was prepared in QGIS 3.28.1, and the files were imported into Maxent for habitat modeling, to enhance accurate predictions of rice crop distribution under different climate scenarios. For suitability analysis, Ecological Niche Modeling (ENM) technique in conjunction with maximum entropy model (Maxent) were used to assess the ecological niche of paddy rice, potential benefits and viability of AWD practice for Eastern region, considering factors such as water availability, soil characteristics, and climate conditions. The results show that 5 major environmental predictors: organic carbon stock (OCS), volume fraction of coarse fragments (CRFVOL), available water (AW), exchangeable potassium (EXK) and topographical wetness index (TWI) and precipitation of the warmest quarter (BIO18) were the most influential predictors in evaluation of AWD. The findings from Maxent model for potential suitability distribution of irrigated rice in Eastern Uganda indicates high-performing metrics with area under the operating characteristic curve(AUC) and percentage correctly classified(PCC) on training data with> 92% and > 90%, respectively. The percolate rates ranging from 1- 5mm/day was found unsuitable for AWD in wet season with rainfall amount greater than 20mm/day and suitable in dry season under all percolates rates. The AWD was found more suitable with increasing percolation rates and region has 70.4% of sand clay loam texture soils class favoring paddy cultivation due to its high percolation rates. The study is a guide into suitability analysis of AWD and provide insights of the potential benefits and limitations of adopting AWD irrigation in Uganda, as a foundation for pilot implementation, and scaling up of the practice in paddy rice fields. Therefore, this is a supportive tool to the decision ad policy makers, irrigation engineers and government for development of sustainable water management strategy that enhance reduced water consumption, mitigation of greenhouse gas emissions and expansion of paddy rice production for food security in Uganda.