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In arid regions, water resources are limited; thus irrigation water use needs to be optimized. As a first step, more precise calculation of crop water use is essential. Crop water use, also known as crop evapotranspiration (ETc), is influenced by the prevailing meteorological conditions, available moisture in the soil, crop species and growth stage. The influence of the meteorological conditions on crop water needs is given by the reference crop evapotranspiration (ETo) and the relationship between the ETc and ETo is termed as the crop coefficient (K-c). The K-c values are affected by agro-meteorological factors, soil characteristics and the agronomic techniques that affect crop growth. Consequently, the use of Kc values developed in other regions may need modification to accurately estimate crop water requirements. Thus, the development of region-based K-c values could be used to accurately estimate crop needs and such values can reliably be determined using weighing lysimeters. A weighing lysimeter was installed at the experimental farm of the International Center for Biosaline Agriculture (ICBA), Dubai, UAE (25 degrees 06'31 '' N; 55 degrees 22'59 '' E). Two potential forage crops of this region, namely pearl millet and sorghum, were tested in the lysimeter during 2008 and 2011, respectively. The data from the weighing lysimeter provided ETc values of the tested crops. The ETo values were calculated using the FAO Penman-Monteith equation using the weather data of the ICBA. The obtained singled (time-averaged) K-c values of pearl millet were 0.28, 1.04, and 0.59 for the initial, mid-season and late-season growth stages, respectively. For sorghum, the corresponding K-c values of three growth stages were 0.65, 1.10, and 0.88, respectively. These values can be used in developing K-c curves for predicting ETc.