Located in the basalt desert of northeastern Jordan, Early Bronze Age (EBA) Jawa is regarded as one of the major settlements in the Middle East during the 4th millennium BCE. In addition to a sophisticated water storage system, the existence of three complex agricultural terrace systems based on runoff and floodwater irrigation in the close vicinity was recently revealed.This paper investigates the impact of these water management strategies on harvest yields and the scale of the ‘on-site’ crop production at Jawa by applying a crop simulation model (CropSyst). Simulations for the cultivation of winter barley, winter wheat and lentils were performed for the period from 1983 to 2014. To simulate the different runoff irrigation schemes, a curve-number-based rainfall-runoff model was applied. To estimate the number of people that could have been supplied by the local food production, simple calculations based on metabolic calorie requirements and agricultural and pastoral production rates were conducted.This study shows that the runoff farming systems of EBA Jawa are relatively effective under current rainfall conditions. Even during dryer seasons, the simulated crop yields are much higher under runoff irrigation/floodwater irrigation than under non-irrigated conditions. On average the crop yields increase by 1.5 to 6 times, depending on crop type and runoff irrigation level. Moreover, a marked decrease in crop failures could be observed. The total crop and animal production could have satisfied the nutritional requirements of about 500 to 1000 persons per year. Considering the estimated maximum population for EBA Jawa, ranging from 3400 to 5000 people (Helms, 1981), local production did not meet the basic needs of all inhabitants. This indicates that trade might have been an important branch of Jawa's economy in order to supplement food resources. Moreover, former population estimates for ancient Jawa might be overstated.