The basin system of irrigation in the Nile Basin is not reliable because

The basin system of irrigation in the Nile Basin is not reliable because it depends on the flow of the Nile in a particular year. The amount of water flowing in the Nile River can vary greatly from year to year due to changes in weather patterns, such as drought or heavy rainfall. This variability makes it difficult to plan and manage irrigation using the basin system, as farmers cannot rely on a consistent and predictable supply of water. Additionally, the basin system may not be suitable for certain crops, and requires significant labor to construct and maintain. Overall, the unpredictability of the Nile's flow makes the basin system of irrigation less reliable than other methods of irrigation that do not rely on natural water sources.