Rainwater harvesting: A gardening necessity in semi-arid regions

This research aims to introduce the water supply method required for pistachio orchards in semi-arid climatic regions using the rainwater harvesting technique. For this purpose, a rain catchment system with an area of 1000 m2 was constructed at the Tasuj Station site. Based on the mean annual rainfall of the region, runoff threshold, runoff coefficient for insulation surfaces and the area of the catchment system, water storage pool was designed and constructed with a nominal capacity of 280 m3. In addition, a geomembrane cover is used to insulate the surfaces of the rain catchment system and the water storage pool. To reduce agricultural water consumption and increase productivity, the drip irrigation method with gravel filters was used to irrigate pistachio trees from harvested rainwater. The results showed that from the total rainfall of 267 mm, about 227 m3 of water was harvested from rainfall in the year 2021. According to the findings, the per capita water consumption of each fruitful pistachio tree has decreased from 8.65 m3 in the usual drip method to one m3 in the drip irrigation method with gravel filters; without having a negative effect on production yield. The simultaneous use of rainwater harvesting techniques and drip irrigation methods along with gravel filters will reduce the pressure of groundwater resources exploitation and increase the irrigation water efficiency. The results of this research were introduced to the farmers of the region in the form of educational-promotional workshops, which have been well accepted.