115 Geo-Eco-Marina 28/2022 1. INTRODUCTION Water demand is noticeably increasing as a result of global population growth, climate change, and socioeconomic factors, such as industrial development, improved sanitation, and domestic waste management (Ferroukhi et al., 2015). The global population has grown from 3.03 billion in 1960 to 7.38 billion in 2015 (Roser et al., 2013). To support this rising population, agricultural production tripled between 1960 and 2015 by employing chemical fertilizers and pesticides, regulating water supplies, and adopting new farming practices such as mechanization (FAO, 2017). This took a signifcant amount of water and energy. Agriculture is the major user of the global water supply, accounting for an average of 70% of all global water withdrawals (Postel and Vickers, 2014). The world population is expected to reach 9 billion people by 2050 if current trends continue (Cole et al., 2018). Feeding this population will necessitate a 60% increase in food production over 2015 (Bene et al., 2015). Nexus thinking evolved out of an awareness that natural resources are beginning to constrain economic growth and human well-being objectives signifcantly. The pressure on resources may eventually result in shortages, jeopardizing people’s access to water, energy, and food, impeding economic development, causing social and geopolitical DEFINING A WATER-ENERGY-FOOD NEXUS FRAMEWORK FOR WATER ALLOCATION IN THE LOWER DANUBE BETWEEN IRON GATES AND ZIMNICEA SANAULLAH SALAM 1 , IOANA POPESCU 1 , ALBERT SCRIECIU 2 1 IHE Delft Institute for Water Education, PO Box 3015, 2601 DA Delft, the Netherlands e-mail: sanaullah.salam@yahoo.com, i.popescu@un-ihe.org 2 National Institute of Marine Geology and Geo-Ecology (GeoEcoMar), 23-25 Dimitrie Onciul St., 024053 Bucharest, Romania e-mail: albert.scrieciu@geoecomar.ro DOI: 10.5281/zenodo.7491459 Abstract. Water consumption is rising due to global population growth, climate change, and other socioeconomic factors. The race to extract more water to meet the demands of various sectors is intensifying, making equitable water allocation challenging. An efort was made in this study to assess the water supply and demand gap among several sectors, namely energy, agriculture, and navigation in the lower Danube stretch, where water is shared by Serbia, Romania, and Bulgaria. The main study was conducted on water allocation needs for various sectors. To understand the water supply and demand balance under diferent conditions, three alternative scenarios were generated: dry, normal, and wet year periods. The Water Evaluation and Planning Model (WEAP) software tool was used to estimate the demand and supply gap in the research area for both energy production and irrigation, and a hydraulic model was used to determine the water depth corresponding to the fow remaining in the river after the withdrawals for energy and irrigation. The hydraulic model was based on the US Army core of Engineers tool HEC-RAS. In terms of water demand for energy production, the fndings indicate that over a calendar year, the highest water demand is fulflled during the month of April, while September has the lowest demand fulflment. No water defcit has been found for agriculture water use in any of the defned scenarios, given the fact that available water in the system is much higher than the required crop water requirement (cwr) throughout the year. According to the hydraulic model results, water depth is rather low in dry years, which will have a detrimental impact on navigation. Key words: water allocation, planning, hydraulic modelling, crop water requirement, lower Danube, WEAP, HEC-RAS