<p>The study was conducted at Bontanga irrigation scheme in Northern Region of Ghana to know the extent of water losses in the scheme, identify deficiencies leading to water losses, propose solutions for reduction of water losses, and project the impact of water losses on water demand using Water Evaluation and Planning (WEAP) model. Assessment of water losses was based on conveyance, distribution, in-field, and total water losses. Out of the seasonal irrigation water supply of 8,391,118.37 m³, total water losses of 5,766,524.23 m³ (conveyance losses: 1,208,321.04 m³, distribution losses: 2,657,635.02 m³, and in-field losses: 1,900,568.17 m³) were recorded, representing 68.70% of the seasonal inflow into the irrigation system. Total water losses were beyond the acceptable limit of 40% for the surface irrigation system. Such significant water losses were attributed to lack of proper maintenance on canals, under-utilization of flow measuring structures, excessive lateral canal tailwater losses, and poor water management at field level. Without efforts to reduce water losses, WEAP model results revealed that unmet water demands are likely to reach 2,482,519 m³ by 2030. However, by reducing total water losses from 68.70 to 40%, an average seasonal water saving of 3,894,597.86 m³ is projected to be achieved during the simulation period from 2024 to 2030.The study has enlightened the significance of effective water loss management to meet competing water demands in the face of a changing climate. Future studies should investigate an in-depth synergy between crop water productivity and system’s water losses in the study area.</p>