As much as 90% of Yemen's water use is in agriculture, with irrigated farmland increasing from 37,000 hectares in 1970 to 407,000 in 2004. Before the 1970s, traditional agricultural practices had a sustainable balance of use and recharge:.  Household water in Sanaa was supplied by shallow wells, and the relative scarcity of water led to people using gray water for watering gardens. Meanwhile, agriculture in the surrounding rural areas was watered by rainfall, with terracing and flood diversion systems making as much as possible out of the limited rainwater. However, after the introduction of deep tube wells and the identification of the Tawilah aquifer, there was an explosion of agriculture in the Sanaa area. By 1995, there were over 5,000 wells in the Sanaa area; as of 2010, the number was about 13,500. At the same time, traditionally grown, drought-resistant crops have been largely replaced by more water-intensive cash crops such as citrus, bananas, grapes, vegetables, and especially qat, which as of 2010 accounted for 6% of Yemen's entire GDP. In the Sanaa area, 27% of all farmland was dedicated to growing qat; by 2010, the number had increased to around 50%.