Assessing the impacts of climate change on rain fed agriculture and the use of rainwater harvesting for mitigating its effects in Teso sub-region.

Abstract

The most severe effect of climate change is the alteration of the hydrological cycle and extreme events which in turn affect rainfed agriculture. It impacts the quantity and quality of water resources at both spatial and temporal scale, according to IPCC 2001, African countries are more vulnerable to these changes due to lack of institutional capacity and low levels of economic development. In Uganda, most of the population depends on rainfed agriculture. The study assessed the impacts of climate change on rainfed agriculture in Teso sub-region. In this study, the impacts of climate change were assessed using the downscaled climate projected data from the NorESM1 General Circulation Model (GCM) in two scenarios RCP4.5 and RCP 8.5 for 2040-2060 period in Teso subregion. The study applied the Man-Kendall (MK) test using the XLSTAT software 2019, to calculate the variation in the rainfall and temperature in the observed and predicated data (trends) over the region and the detection of the magnitude of the trend (slope) was calculated using the Sen’s slope estimator method (change per year). The variability in precipitation was calculated using the coefficient of variability and the variability index to determine the dry years and the severity of the droughts, the FAO CROPWAT 8.0 and CLIMWAT 2.0 simulation software’s were used to calculate the crop water demand and the available future runoff. The analysis showed generally, the temperature was projected to increase by 1.18oC at RCP 4.5 and 2.7oC at RCP 8.5. There is an insignificant decrease in total annual precipitation in the projected 21-year period of 26% and 23.9% at RCP 4.5 and 8.5 respectively. The inter annual variability was calculated as 14% in the baseline, and 17% and 19% at RCP 8.5and 4.5 respectively. The projected dry years where 2041, 2042, 2046, 2057 and 2041, 2046, 2048, 2052, 2060 for RCP8.5 and 4.5 respectively. The potential rainfall runoffs were 614mm, 728mm, and 781mm per year while the crop water demand was 301.5mm, 555.6mm and 544.4mm per year under the baseline and RCP4.5 and RCP8.5 scenarios respectively. From these results, it was evident that the temperature in sub-region is rising, and this leads to an increase to crop water demand thus affecting agriculture. There is both a horizontal and vertical shift in the rainfall patterns especially the start dates of the rainy seasons and the associated extreme weather events. The projected increase in temperature was 1.18oC at RCP 4.5 and 2.7oC at RCP 8.5, However, the increase in precipitation statistically insignificant overtime. The potential rainfall runoff is higher than the crop water demand in all the scenarios and therefore, sufficient rainwater runoff can be harvested to satisfy the crop water demand.