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This is an image of a reconstructed Byzantine Farmstead at Shivta. Note the two stone-built dams in the bottom of this valley—one on the left, the other near the right-center of the image. This area of the Negev receives only 3.5 in. of rain in an "average" year. Water, and soil(!), from the surrounding hills were/are diverted to the area behind the dams where topsoil and water collected. By concentrating the runoff here, 3.5 in. rain was converted to about 10 in.! Thus crops were able to grow there!
In this image, note the olive tree in the center and behind it are several carob trees! All grown without mechanical irrigation! And, this farm has been untended for years and the trees are still growing!
Contrary to previous opinions, the agricultural systems, that fed winepresses such as this, instead of dating to the Nabatean Period, actually were built during the Byzantine Period—beginning in the fifth century AD and continuing in use until the late seventh or early eighth century AD.
Please also note the barren surrounding countryside. This area only receives 3.5in of rain per year. This picture was taken in July—the middle of the dry season in Israel.