The effect of over or under irrigation on vegetables is the reduction in yield. The study carried out in the Black Volta Basin that falls within the administrative boundaries of the Upper West region of Ghana, sought to ascertain the potential for increasing agricultural water productivity under various agricultural water management interventions being used for dry season gardening and livestock rearing. Seven sites were selected for detailed studies. Primary and secondary data were collected through desk studies, key informant interviews, questionnaire administration, focus group discussions, field observation and measurements. Statistical and scientific tools such as Microsoft Excel and CROPWAT 8.0 model were used in processing, generating, and analyzing the raw data obtained. The results revealed that agricultural water management intervention in which supply and application of water is under gravity and capillary action gave crop water consumption factors of about 87% each for both tomato and pepper, hence, over irrigation as compared to FAO values for semi-arid to arid conditions under optimal performance should be zero. The riverine intervention using water pumps, pipes, and hoses gave crop water consumption factor of about -8%, thus a water deficit being experienced by pepper. Shallow wells with line and bucket intervention gave crop water consumption factors of about 6% and 24% for tomato and pepper respectively. The intervention in which water pumps are used in lifting water directly from small reservoirs gave crop water consumption factors of about -10% and -25% for tomato and pepper
respectively. The intervention that used water pumps to lift water from main canals of small reservoirs to the fields gave crop water consumption factors of between 36% to 16% for tomato and 9% to -25% for pepper. The physical and economic productivities from the results are generally low as compared to the FAO standards for arid and semi-arid conditions. The agricultural land productivity was also very low in the study area. But livestock water productivity was high although the animals were not engaged in any dry season agricultural activities. Hence, the study concludes that the potential to increase agricultural water productivity exists for all the interventions considered with the highest in gravity and capillary action based systems. This is possible if water resources engineers and managers with in-depth knowledge in agriculture water management are engaged to plan, operate and manage such projects.