Eveneari grew up as Walter Schwarz close to Marburg and Buchenau. He studied botany at Technische Universität Darmstadt and received his doctorate 1927 under the auspices of Martin Möbius. He fled from Germany on 1. April 1933 and was active in Jerusalem as professor at the Hebrew University of Jerusalem. He was a brother in law of writer Gerson Stern, his parents were German Jews and merchants from the Lorraine, which had opted for Germany after World War I and were forced to immigrate after Metz became French again. Evenari joined Hagana and fought in the Israeli War of independence.

His works on the Nabataeans runoff rainwater management were crucial for modern Israeli agriculture and explained as well how the Nabataean culture was able to supply thousands of inhabitants in a similar arid climate. Evenari showed that the runoff rainwater collection systems concentrate water from larger areas and in so far allow to grow plants with higher water needs in the given arid environment. The mechanism explained a variety of ancient agricultural features, terraced wadis, channels for collecting runoff rainwater, and the phenomenon of "Tuleilat el-Anab", grape mounds.

Evenari himself cared about the cultural heritage of the bedouins but saw them more as 'fathers' than 'sons of the desert'. He worked as well on Algae fuel, a special sort of renewable resource and biofuel.