Large gaps between actual and potential crop yields reflect the presence of socio- environmental conditions that limit production. In much of the Nile, lack of farmers’ access to available water is the prime constraint to crop production. With increasing numbers of people and their growing demand for food, combined with little opportunity to access new water sources, great need exists to make more productive use of agricultural water. Based on Crop Water Productivity, the spatial distribution of the basin can be divided into three zones: the high productivity zone, the average productivity zone and the low productivity zone. The WP index serves as a useful indicator of the performance of rain-fed and irrigated farming in water-scarce area
High productivity zone
The high productivity zone includes the delta and irrigated areas along the Nile River in the northern part of the basin. This zone is characterized by intensive irrigation, high yields and high-value crops. These characteristics collaboratively contribute to the high level of the WP attained and art’ in fact correlated. Access to irrigation results in higher yields; higher yield results in higher incomes; and higher incomes result in higher investment in from inputs by farmers.
Average productivity zone
The average productivity zone consists of two major areas, one in the eastern part (Ethiopia mainly) and the other in the southern part (areas around the Lake Victoria). Despite the fact that most of the areas in this zone receive relatively good amounts of rainfall, the predominantly rain fed agriculture has rather low yields and, therefore, relatively low Water Productivity. The fact that rainfall is sufficient to grow crops in this zone opens a wide prospect for improvement in this region. Two parallel strategies that could be applied are, first, improving farm water management and, second, promoting irrigated agriculture. The main obstacle for irrigated agriculture in this zone is accessibility to water rather than its availability. For example, in Ethiopia, due to lack of storage infrastructure the majority of generated run-off leaves the country without being utilized. Controlling these flows and diverting the water to farms can drastically improve both land and water productivity
Low productivity zone
The low productivity zone covers the central and western part of the basin. Agriculture in this zone is rain-fed and it receives a low amount of rainfall in most areas rainfall amounts received cannot meet the crop water demands and therefore crops suffer from high water stress. As a result, yields are extremely low. In this zone improving water and land productivity is contingent upon expanding irrigated agriculture. A good example that shows how irrigation can bring improvements is the Gezira scheme in Sudan.
This scheme is located in the same zone (geographically) but irrigation has resulted in significantly higher WP in the scheme compared to its surrounding rain-ted areas. However, due to poor water management, WP in the Gezira scheme is much lower than in irrigated areas in northern parts of the basin (i,e. in the delta).