Adaptation to climate change impacts on crop water requirements in Kikafu Catchment Tanzania Stella C. Rotich and Deogratias M. M. Mulungu ABSTRACT Agricultural activities are the main livelihood for about 70% of Tanzania’s population, with women being the main players. Crops need water (crop water requirements, CWRs) for their growth and production, which can either be rain-fed or irrigation sourced. However, climate change has affected the hydrological cycle, particularly water available for agricultural crops. Since impacts and consequently adaptation are site-specific, an assessment of the effects of climate change on maize water requirements in Kikafu sub-catchment was conducted using a crop simulation model, CROPWAT. Accordingly, climate scenarios were obtained from A2 emission scenario using three Global Circulation Models (GCMs). These scenarios were downscaled at two site locations using the Long Ashton Research Station Weather Generator model. The baseline period for the change analysis was 1971–2000. The CWRs are projected to increase by 3.8% in the 2020s and 7.1% in the 2050s at the Moshi Airport and 19.9 and 22.4% at Lyamungu station, respectively. More impact is projected to be during 70–80 days of the development stage and the entire mid-season (81–140 days) whereby the temperature will be high but with low precipitation. With the increasing CWRs, better adaptation measures are increase crop diversification, restore soil organic matter and change cropping systems as established through the multi-criteria analysis. Stella C. Rotich Deogratias M. M. Mulungu (corresponding author) Department of Water Resources Engineering, University of Dar es Salaam, College of Engineering and Technology, P.O. Box 35131, Dar es Salaam, Tanzania E-mail: dmulungu@udsm.ac.tz Key words | adaptations, climate change, downscaling, Kikafu River catchment, LARS-WG, maize water requirements INTRODUCTION The ever changing climate constitutes a major challenge to mankind today. Various sectors of the economy, such as agriculture, energy, tourism, are increasingly being affected by climate change. Water and food security are under severe threat escalated by increased world population and food demand. Consequently, most of the water resources are being depleted and the agricultural production decreas- ing with the reduction in arable lands. On the whole, climate change is a global problem with its effects being severe in developing countries where the majority of the people are poor and depend primarily on rain-fed agricul- ture (Morton ). As the bulk of the populations in Africa depend on rain-fed agriculture for food and their live- lihoods, they are vulnerable to the climate effects. Climatic data indicate that the continent experiences decreasing and increasing trends of rainfall and temperature, respect- ively (IPCC ). Studies have predicted that the average global temperature may increase by 1.4–5.8 W C and there would be a substantial reduction in freshwater resources and agricultural yield by the end of the twenty-first century (Tadross & Wolski ). Moreover, climate change has resulted in an increase in globally-averaged mean annual air temperature and variations in regional precipitation, with these changes projected to continue intensifying in future (Solomon et al. ). Increased temperatures lead to increased evapotranspiration, which affects water avail- ability for crops (Holmén ). In some African regions, the projected climate change is likely to increase water 1 © IWA Publishing 2017 Journal of Water and Climate Change | in press | 2017 doi: 10.2166/wcc.2017.058 Uncorrected Proof