Flood water harvesting, also sometimes referred to as spate irrigation, is a method of informal irrigation using the floodwaters of a normally dry water course or riverbed (wadi). These systems are in general characterized by a very large catchment upstream (200-5000 ha) with a ratio of “catchment area : cultivated area = between 100:1 - 10 000:1. There are two types of spate irrigation: 1) floodwater harvesting within streambeds, where turbulent channel flow is collected and spread through the wadi where the crops are planted; cross-wadi dams are constructed with stones, earth, or both, often reinforced with gabions; 2) flood water diversion, where the floods - or spates - from the seasonal rivers are diverted into adjacent embanked fields for direct application. A stone or concrete structure raises the water level within the wadi to be diverted to the nearby cropping areas.