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Water allocation is a key component of good water management in an irrigation system. Water imbalance between upstream and downstream has been a major issue at Tanjung-Karang Rice Irrigation Scheme Malaysia. This study applied the HEC-RAS model to estimate water for supply and analysed its allocation to the demand in the scheme. Water demand was computed based on water requirement, effective rainfall and seepage/percolation. Results of R2, NSE, PBIAS and RSR during the model calibration and validation were 0.66, 0.64, 0.94 and 0.60; and 0.65, 0.59, 1.77 and 0.64, respectively. The irrigation scheme was under-supplied from January-March and over-supplied from April-June during the off-season. While in the main-season was under-supplied from July-September and over-supplied from October-December. Similarly, the excess water during the off and main seasons for the period was 40.10 and 52.40 Mm3 respectively. Whiles the deficit water during the same seasons was 52.46 and 53.14 Mm3, respectively. This suggests providing an adequate storage facility, which could store excess water during low water demand and use it in the period of water shortage. The developed model could therefore assist in estimating the over/under-supply with respect to the demand thereby storing the excess for use during the period of high demand.&nbsp

Irrigated agriculture has been identified as an important practice to achieving food security and socio-economic development in the face of rapid population growth and climatic uncertainties. In northern Nigeria, irrigation has long been identified as the key to achieving the much-desired increase in food production to meet the ever-increasing population. However, the existing irrigation schemes encountered several challenges coming from different dimensions including economic, social, environmental, institutional and technological. To attain sustainable crop production, this paper attempts to uncover the underline challenges confronting irrigation schemes in northern Nigeria that cut across sustainability pillars. The findings revealed that irrigation schemes contributed immensely toward achieving food security and improving the wellbeing of rural dwellers. However, the huge investment in large- and medium-scale irrigation schemes have resulted in massive economic losses. This could be attributed to their under-utilization, poor management and abandonment although few ones are performing remarkably well. The study recommends the need to adopt new water allocation and application methods that can improve water use efficiency, users-managers join approach (participatory), effective and competent institutions which include improved monitoring, evaluation and surveillance systems, frequent policy review to suit the situation, law enforcement, and timely sensitization and awareness campaigns.