The Sweetest Waters

On May 31^st I joined once and future colleagues at the Office of Arid Lands Studies to attend a talk on Water Harvesting Impact Assessment in Dry Areas of Tunisia, by Dr. Mohamed Ouessar of the Institut de Regions Arides, Tunisia. He wrote an article for the Arid Lands Newsletter several years ago. Following Dr. Ouessar’s presentation, several of us went to lunch, then I joined Dr. O. and the editor of the ALN, Katherine Waser, to do a tiny tour of water harvesting efforts in Tucson. I was immensely flattered when Katherine proposed that we visit MY site.

In the end, my home visit was a chance to cool off and drink homegrown lemonade between visits to some REAL water harvesting sites in Tucson. But it was fun to share my fledgling efforts and get some expert advice on some of my rather unscientific and disorganized approaches to water catchment. While we were outside admiring my water collection cisterns, a neighbor pulled up to the side of the road and ran toward us. “Uh, oh,” I thought, cynically bracing myself against an accusation of ugliness in my sustainability improvements. Instead, she said, “I am so glad you’re outside! I want one of those!” Happily I met another kindred spirit and printed off some specs and contact information for her. She said she has a lovely yard and she wants to keep it looking lovely while minimizing her use of groundwater. It made my day. This stuff is contagious! She’s the third neighbor I’ve met as a result of my installations—a nice side effect, yes?

Visits to the homes of Brad Lancaster and Barbara Rose framed my little lemonade party. These are two leaders in the permaculture movement--teachers and role models among the growing community of people seeking to reduce their impact on the earth. I’m still distilling all I learned while I tagged along and listened to the conversation and information exchange between an international expert on water harvesting and these local experts who have had an enormous positive influence on my own community.

On that lovely day, I learned a new word: eremology: the science of dry areas. I like using esoteric titles to describe my professions, so now I can say I’m a gypsy scholar, word smith, librarian’s apprentice, and eremologist.

As long as people have inhabited and cultivated dry lands, they have harvested water. Water harvesting is the practice of collecting water from an area that is treated to increase runoff from rainfall or snowmelt for beneficial use. Examples of early water harvesting technology exist in Southern Jordan (5000 years ago), Southern Mesopotamia (4500 BC), the Negev and Yemen (1000 BC), Tunisia, Egypt and Morocco.

Some methods for water harvesting include collection of water from the atmosphere (fog and dew harvesting), from overland flow, and groundwater. People have imitated a kind of beetle which positions itself so that it can collect, condense and consume moisture from the fog that passes over its body. There is also a desert plant called walasia (sp?), which has unexpectedly large leaves, for a desert plant, which it uses to collect condensed fog. In the Canary Islands, humans use volcanic ash to condense dew—it infiltrates the soil to produce onions, grapes, and figs with no irrigation. The ash also serves as mulch to reduce evaporation.

Rainwater can be harvested from rooftops in micro- or macrocatchments (i.e. the size of the catchment). Water can be stored in jars, tanks and cisterns. Agriculture can make use of land contouring and plant placement to make the best use of precipitation. A subterranean dam made of sand can be drilled into the soil to obstruct the movement of water, to create a shallow aquifer. The water is stored in the area upstream of the dam, collecting water for use in agriculture. Small crescents can be shaped to collect water from slopes, preventing erosion and creating terrace-like areas for planting. Diversion dykes can be built with lateral spillways to redirect natural impluvium. Simple cages, filled with rocks, can be used to form blocks to make small check dams to reduce the velocity of runoff, giving more time for the water to seep into the ground to recharge the aquifer. Groundwater recharge wells can be used to directly recharge the aquifer, though silt builds up in these structures quite rapidly, reducing their effectiveness.

These are the sorts of implementations that have taken place in the dry areas of Tunisia. I’ll spare you all the intricacies of Dr. Ouessar’s Impact Assessment, but I will share this: in the study area where he and his team collected thirty years of data, the results of the water harvesting practices were quite nice: there was almost complete elimination of outflow, with increased percolation and seepage, with a slight increase in evapotranspiration. This had a positive impact on crop production and aquifer recharge. However, there were some not so pleasant side effects downstream from the water harvesting area. Cutting the runoff from upstream decreased the quality of halophyte vegetation in the saline depression at the very bottom of the watershed. This vegetation provides winter forage for livestock, and the overall quality of that area has decreased as a result of water savings upstream.

Dr. Chuck Hutchinson, director of OALS, asked to what degree local communities are involved in restoration and rehabilitation of the ancient water harvesting technology in their areas. Dr. Ouessar said that these structures are built and maintained by local populations, but there is the problem of migration as people move to cities to pursue a better life. He said the Tunisians do have one little secret weapon in the battle to preserve the ancient technologies for the benefit of their communities: they have a strong connection to place, so that even when they leave, they retain an investment in their home lands. They honor the property of their ancestors, making them more likely to put forth effort to preserve and improve the land and its associated assets. Water harvesting systems are regarded as part of the landscape, part of the history of the place. Some areas use the structures in ecotourism.

I know that first-hand; I visited some of these ancient structures in 199? with classics professor Dr. David Soren. We visited many of the sites described in his book: Carthage (David Soren, Aicha Ben Abed Ben Khader and Hedi Slim. Simon and Schuster/Touchstone: 1990). Perhaps even then I was taking in what I saw, letting that knowledge percolate down into a fundamental way of living influenced by ancient wisdom and pragmatism.

One of my favorite moments from that whole day was when Dr. Hutchinson told of his interviews with the elders of a community in Spain, who said, “The sweetest waters are in March.” The last rainwater of the season came into cisterns from rooftops that had been washed clean with the season’s rainfall. Perhaps the sweetest is that which is soon to be absent for a while, or forever. Maybe the sweet blessing of rainfall in the desert will inspire more and more people to use various time-tested methods to collect it for our own beneficial use.