Uri Nachshon

Dr. Gabriel Rubanenko, Prize for Excellence in Research, 2006

Department of Environmental Hydrology and Microbiology
Zuckerberg Institute for Water Research
Jacob Blaustein Institutes for Desert Research
Ben-Gurion University of the Negev

My name is Uri Nachshon, and I am 29 years old. I am the older brother for my sister Yael and my brother Gal. I was born in a small, rural village, near Tel-Aviv. Since childhood my parents (Shalom and Didi) took us for many trips around the country and thanks to them I got to know and love Israel; its nature and landscapes. In my family we use to say that "the north of Israel is beautiful, but the problem is that the trees are blocking the view". Maybe, upon this joke, my love for the Negev developed.
At age 14 I moved to a special Environment-Nature oriented high school at Midreshet Ben Gurion (without knowing that 10 years later I would return to the same place to do my Master's degree). My four years at this special high school were full of experiences and adventures.
As all Israelis, I joined the army at the age of 18 and served for 4 years, in a combat unit of the armored forces.
Following the "Israeli Tradition", after the army I flew away for one year to see the world. I traveled in New-Zealand, Australia and Southeast Asia. This trip was a great experience with a corny and important lesson, that there is no place like home.
Four years ago I started my Bachelor's degree in geology at the Ben-Gurion University, in Beer-Sheva. After that I started my Master's degree in Hydrology, at this wonderful institute in Sede-Boker campus.
For the last few years I have lived with my girlfriend Lihi at Kibbutz Beit-Kama, 20 minutes from Beer-Sheva. All I can ask is to have many more years of learning, exploring and satisfaction, as I have found in Sede-Boqer.

Description of research:

Air Convection Flows in Rock Fractures; Patterns and Characteristics

Supervisors: Dr. Noam Weisbrod, Dr Maria Dragila

Fractures in rocky terrain, especially in arid regions play a major role in the hydrological cycle. Recent studies have found that a significant amount of water evaporates through the fracture walls. As a result of the evaporation, salts are being deposited along the fracture walls. The salty crust can accumulate and clog the fracture or dissolve in rain events and cause infiltrating water to reach the ground water.
A conceptual model was suggested by Weisbrod and Dragila to explain the massive evaporation through the fractures. They suggested that air convection flows appear at the fractures due to thermal differences between the fracture and the atmospheric air. These convection flows take with them water vapor and increase the evaporation.
My research goal was to prove the presence and to quantify the air convection flows in the fractures. The first part of my research was held in the laboratory, where I simulated a natural fracture. I used smoke to visualize the convection flows and by analyzing the smoke flows I learned about the convection velocities, patterns and dimensions. The second part of my research was held in the field where I measured the thermal distribution in a natural fracture. The thermal data showed that the convection cells also appear in natural fractures. The convection cells dimensions and characteristics at the field where in agreement with the laboratory results.
The laboratory experiments and the field measurements proved that the convection cells do appear and results the intense evaporation.
This research can lead to some interesting and practical applications such as extraction of contaminant gases from the soil by using the relatively high mass transfer rates of air through the fractures.