In the absence of permanent rivers or bodies of water, streams and groundwater, desalinated seawater and very scarce surface water must supply the country's needs. In eastern Arabia and in the Jabal Tuwayq, artesian wells and springs are plentiful. In al-Ahsa a number of large, deep pools are constantly replenished by artesian springs as a result of underground water from the eastern watershed of the Jabal Tuwayq. Such springs and wells permit extensive irrigation in local oases. In the Hijaz, wells are abundant, and springs are common in the mountainous areas. In Najd and the great deserts, watering places are comparatively fewer and scattered over a wide area. Water must be hoisted or pumped to the surface, and even where water is plentiful, its quality may be poor.