The agriculture sector is important for Iran's economy, providing 13% of GDP and 22% of employment. Most of Iran's arable land of 19 million hectares is rain-fed, receiving an average of 200-600 mm of precipitation annually in uneven seasonal distributions. Currently, rain-fed areas contribute 10% of Iran's total annual crop production of 8.7 million tons, including 31% of wheat, 34% of barley, and 48% of pulse crops. Optimization of rainwater use could help increase agricultural output and rural incomes in Iran's semi-arid rain-fed regions.