In spring-irrigated areas water can be attached to land in the form of 'turns', which give rights to divert the canal into the field for a fixed period of time. The 'turn' can however be detached from the land and sold or rented separately. This landowner 'precedence' has permitted the private development of deep tubewell extraction, which is in some ways in conflict with Islamic principles. As far as the production of qat is concerned, no official figures are available, but there have been estimates that at least one-fourth of the irrigated land is under qat production. Production of vegetables, potatoes and fruits have increased significantly.
Pulses also retain an important place.
However, no figures on the area covered by all irrigated crops are available for the country as a whole. Salinization due to irrigation exists in several regions, but no figures are available. No drainage systems are reported to exist. The successful and sustainable exploitation of the water resources in Yemen is threatened. The most serious and obvious problem is the rapid depletion of groundwater resources.