Columbia subject headings:
Harvard subject headings:
Africa, North--Economic conditions.
Agriculture--Economic aspects--Africa, North.
Irrigation--Africa, North.
Irrigation--Government policy--Africa, North.
Water resources development--Africa, North.
Water resources development--Government policy--Africa, North.
Water--Africa, North.
Water-supply, Agricultural--Africa, North.
Princeton subject headings:
Irrigation--Africa, North.
Irrigation--Economic aspects--Africa, North.
Water--Africa, North.
Water-supply, Agricultural--Africa, North.