File:Alluvial fan in Iran.jpg

English: Seasonally dry salt lakes and the traces of ephemeral streams occupy many of the valleys of the Zagros Mountains in southern Iran. Much of the time, the rivers and lakes are dry above ground, but subterranean water flows along the same pathways. Where these subterranean streams flow out of the mountains, the water table comes closer to the surface, and it is more readily accessible through wells. This simulated natural-color image of southeastern Fars province in southern Iran shows a dry river channel carving through arid mountains toward the northeast. The dry river spreads out across the valley floor in a silvery fan. A broad belt of lush agricultural land follows the curve of the fan and stretches out along a road that runs parallel to the ridgeline. The valley-ward margin of the intensely green agricultural belt fades to dull green along streams (or irrigation canals). The image was captured by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA’s Terra satellite on October 12, 2004.