The cultivation of domesticated plant species is attested in the Levant as early as the 9^th millennium. There are two types of agriculture: dry, where there is enough rainfall to water crops, and irrigated, where crops need to be supplied with water. Dry agriculture is possible in regions receiving more than 200 mm/m³ of water per year. The driest dry-farming areas could still be supplied with water by irrigation to supplement natural rainfall.