Population growth, increasing demands for food, ever-growing competition for water, reduced supply reliability, climate change and climate uncertainty and droughts, decline in critical ecosystems services, competition for land use, changing regulatory environments, and less participatory water resources governance are contributing to increasing difficulties and challenges in water resource management for agriculture and food. The need for sustainable food security for our global population and the need for preserving the environment, namely natural and man-made ecosystems and landscapes, have created an increased need for integrated, participative and scalable solutions focusing the various levels of irrigation and nature water management, from the field crop to the catchment and basin scales. Meanwhile, challenges and issues relative to water management for agriculture and food have evolved enormously in the last 30 years and the role of active management of the components of the water cycle is assuming an increased importance since their dynamics are key to assure water use sustainability, mainly agriculture and natural ecosystems sustainability. However, different regions face context-specific challenges associated with water scarcity, climate, governance, and population requirements. The main and first challenge is producing enough food for a growing population, which is intimately related with challenges placed to agricultural water management, mainly irrigation management. This paper revises challenges and progress achieved in the last 30 years focusing on irrigated agriculture, mainly water management, and its contribution to food security and the welfare of rural communities.

The proliferation of food, feed and biofuels demands promises to increase pressure on water competition and stress, particularly for Thailand, which has a large agricultural base. This study assesses the water footprint of ten staple crops grown in different regions across the country and evaluates the impact of crop water use in different regions/watersheds by the water stress index and the indication of water deprivation potential. The ten crops include major rice, second rice, maize, soybean, mungbean, peanut, cassava, sugarcane, pineapple and oil palm. The water stress index of the 25 major watersheds in Thailand has been evaluated. The results show that there are high variations of crop water requirements grown in different regions due to many factors. However, based on the current cropping systems, the Northeastern region has the highest water requirement for both green water (or rain water) and blue water (or irrigation water). Rice (paddy) farming requires the highest amount of irrigation water, i.e., around 10,489 million m3/year followed by the maize, sugarcane, oil palm and cassava. Major rice cultivation induces the highest water deprivation, i.e., 1862 million m3H₂Oeq/year; followed by sugarcane, second rice and cassava. The watersheds that have high risk on water competition due to increase in production of the ten crops considered are the Mun, Chi and Chao Phraya watersheds. The main contribution is from the second rice cultivation. Recommendations have been proposed for sustainable crops production in the future.

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.

Selecting appropriate crops and applying deficit irrigation can help increase water productivity in water-limited regions such as the Mediterranean. The objective of this study was to develop water production functions of major cereal and legume crops under the same environmental and management conditions. Bread and durum wheat, faba bean, chickpea, and lentil were grown under full supplemental irrigation (FSI), two deficit irrigations levels of 2/3 of FSI (2/3SI) and 1/3 of FSI (1/3SI), and under rainfed conditions (no irrigation). In average, the actual evapotranspirations (ETs) under FSI were 549, 552, 365, 451 and 297mm, for bread wheat, durum wheat, faba bean, chickpea and lentil, respectively. For the same crops, they were 463, 458, 330, 393 and 277mm for the treatment 2/3SI and 357, 351, 265, 318 and 244mm for the treatment 1/3SI, respectively. In the case of the rainfed treatment, ETs for the mentioned crops were 250, 251, 227, 237 and 215mm, respectively. The experiment was conducted at the ICARDA experimental station at Tel Hadya, near Aleppo, Syria, over three growing seasons from 2007 to 2010. Results showed that, in general, the treatment with 1/3 of FSI gave the highest rate of increase in grain yield and water productivity. The mean grain yield from rainfed, 1/3SI, 2/3SI, and FSI were 1.36, 3.82, 5.18, and 5.70t/ha for bread wheat; 1.24, 3.80, 5.10, and 5.75t/ha for durum wheat; 1.57, 2.35, 2.86, and 3.54t/ha for faba bean, 1.36, 2.63, 3.36, and 3.74t/ha for chickpea, and 0.64, 1.16, 1.42, and 1.58t/ha for lentil respectively. Grain yield reductions due to the application of 2/3SI were around 10, 5, 15.6, and 10.2% of FSI on average for wheat, chickpea, faba bean, and lentils, respectively. Deficit irrigation at 2/3SI increased water productivity compared to rainfed treatments, by 200, 223, 126, 148 and 190% for bread wheat, durum wheat, faba bean, chickpea, and lentils, respectively. However, differences in total water productivity of crops grown under full irrigation compared to deficit irrigation were not significant. Irrigation water productivity ranged from 25kgha⁻¹mm⁻¹ in wheat with 1/3SI to 10kgha⁻¹mm⁻¹ for legumes under the FSI treatment. Unlike legumes, maximizing wheat grain yield caused a decline in water productivity.

As the uncertainty and importance of securing resources increase, the nexus concept is used for integrated sustainable use management planning. In particular, because protected farms are most affected by temperature change, the connection between the heating temperature variable and resources must be analyzed. In this study, a water-energy-food-carbon nexus model that reflected the agricultural characteristics of protected farms was constructed. The crop yield, irrigation amount, and heating energy were simulated, and a sensitivity analysis was performed according to climate change scenarios and heating temperature variables. There was no significant decrease in the yield of food resources even at heating temperatures lower than 12 °C. In contrast, the growing period shortened as the heating temperature increased above 12 °C, which decreased the irrigation amount but tended to increase the heating energy. In addition, lowering the heating temperature standard from 12 °C to 8 °C (or less) is suitable for efficient resource management.