Studies have reported a significant decrease in the use of traditional RWH techniques in many regions (Agarwai & Naraii, 1999; Al-Wadaey & Bamatrf, 2010; Ferrand & Cecunjanin, 2014). This gradual abandonment of traditional RWH systems increased the pressure on other water sources, resulting in water conserva tion problems (Edmunds & Cardona, 2006).

Spate irrigation orfloodwater diversion systems are designed to capture floodwater to improve agricultural productivity and livestock production (NWP, 2007). These systems are among the most impor tant indigenous systems, many of which are still in use today, particularly in dry areas. Diversion weirs used in traditional spate irrigation systems can withstand all or a portion of floods and divert the water to adjacent agricultural areas. This practice can mitigate the problems caused by droughts and floods and slows erosion processes (Edmunds & Cardona, 2006).

Another example of indigenous systems is the traditional system of khooshab, which was used in northern Baluchistan, a region in southeast Iran that receives only 150 mm annual rainfall. Khooshabs are macro-catchment harvesting systems used to utilize flash floods generated from torrential monsoon rainfall during summer. They are constructed on the ephemeral riverbanks and divert floodwater to irrigated areas of between one and 10 ha (Hosseini-Marandi, 2005).

Traditional runoff agriculture has been practiced in Iran for more than 3000 years (Berndtsson et al., 2016). In northeastern Iran, near the border with Turkmenistan, a traditional system known as sowma is still practiced. Sowmas are earth trapezoidal bunds built across relatively flat and wide U-shaped valley beds and parallel to irrigated fields. A typical sowma is 0.5e2 m high with side slopes of 1:1 and 20e100 m of cropping areas between each sowma. The semi-arid conditions in northeastern Iran, which has an annual rainfall of less than 200 mm and no groundwater resources, meant that the Turkmens, who were the ancient in habitants, used the sowma system, which is a macro-catchment RWH system for use for agricultural, livestock, and domestic purposes (Berndtsson et al., 2016; Sheikh et al., 2012).