NMSU professor boosts Afghan irrigation system

Writer: Jay A. Rodman

HERAT PROVINCE, Afghanistan – Military forces from the U.S. and other coalition nations have been in Afghanistan for almost a decade, following the events of 9/11. For much of that period, governmental and non-governmental agencies have also been there, working to stabilize the society through non-military means and repair crucial infrastructure.

Zohrab Samani

NMSU civil engineering professor Zohrab Samani (center, with notebook) participates in the weekly inspection of the reconstruction of Karez Bibi in Herat Province, Afghanistan. (Photo courtesy of Zohrab Samani)

For the past three years, New Mexico State University has headed up AWATT, the Afghanistan Water, Agriculture and Technology Transfer project. The $16 million USAID-funded project is a collaborative effort involving three U.S. partner universities, additional U.S. government entities, non-governmental organizations and Afghan government agencies and other institutions. AWATT’s mission is to help restore Afghan watersheds and irrigation systems, increase agricultural production, create jobs for Afghans and help improve the people’s confidence in Afghan government agencies and programs.

One of many NMSU faculty members to spend time in Afghanistan is Zohrab Samani, a professor in the Department of Civil Engineering with expertise in irrigation systems. In that country, where the economy is largely based on agriculture, the state of the irrigation infrastructure is of great importance.

Samani’s primary assignment during summer and fall 2010 was to oversee the rebuilding of degraded irrigation canals, culverts, diversion dams and feeder tunnels, or “karezes,” in Herat, a province that borders Iran in western Afghanistan. Samani, who has been involved in international project work in numerous countries since 1983, is originally from Iran. He is fluent in Farsi, a language closely related to Dari, one of the two main languages spoken in Herat.

Samani and his team were expected to accomplish their work in a way that improved long-term performance, safety, reliability and ease of maintenance of the infrastructure. A key member of the team was Nazir Ahmad, an Afghan civil engineer hired by AWATT. A Herat native whose degree is from Kabul University, Ahmad made major contributions to both the project’s design and its implementation.

“Priorities included designing the project to meet the long-term needs as defined by the local communities, hiring local contractors and laborers, using local materials when possible, and ensuring the work was done well and at a reasonable cost,” Samani said.

In terms of impact, the highlight of Samani’s project was his work on the karezes. A karez is a horizontal well with a slight upward slant. From the surface, a tunnel is bored into the hillside at a slight upward angle until it taps into a nearby aquifer. The water from the aquifer travels downhill through the karez to canals that deliver it to where it is needed.

“With the karez design, no pumping system is necessary to extract the water; gravity moves it from source to destination,” Samani said. “This helps explain why karezes are such a crucial part of the Afghan irrigation infrastructure – in Herat, for instance, they supply more than 60 percent of the water for farming.”

The karez concept dates back 3,000 years and functioning examples can be found from China to Africa. But the traditional design is not very efficient. Samani estimates that in Herat and places with similar climate, 50-80 percent of the water transported by karezes is lost, either because it seeps away before it reaches the fields or because it flows whenever it is available instead of only when irrigation is needed.

Extensive annual maintenance is another drawback of traditional karezes. Because they are essentially tunnels through dirt, they erode, get clogged and collapse. The average karez in the Shindand District of Herat, where Samani’s project was concentrated, is about a half mile in length and the maintenance work can take a couple of months.

Several karezes were on Samani’s list of rehabilitation projects. His innovative approach, designed to improve the karezes’ durability and efficiency, included lining them with rock or other stable materials after they were dug out, covering them with slabs before burying them again, putting covers on the access wells and adding mechanical water-control features.

The most difficult aspect of the project was to improve the farmers’ access to adequate water when it was most needed. The volume of water flowing through these karezes at any particular time is related to precipitation cycles, snow melt in the mountains and the amount of water held in the aquifers. Traditionally, there has been no way to shut off or regulate the flow. As a result, much of the available water might flow through the system when irrigation wasn’t needed and there was no way to store it for expanded irrigation during the growing season.

The technical breakthrough that Samani came up with involved applying certain well-design principles to the karez. He hypothesized that if the new rock-and-cement lining of the karez segment below the water table were surrounded with a layer of gravel, with periodic slots allowing water to flow through the walls, it should be possible to shut off the karez with a gate at the delivery end without causing it to overflow – the water would flow back into the area surrounding the karez and replenish the aquifer. When water was needed, the karez gate could be opened, either partially or fully, allowing stored water to flow into the canals.

Karez Bibi, in Shindand Province, was the test site for Samani’s karez-closing experiment. He reported that the contractor and local farmers had been skeptical, but they agreed to give the new design a chance. The karez was “closed” for the winter on Dec. 15, 2010 and when water did not overflow the gate, it was clear that the new design was functioning as Samani had predicted.

“This essentially transforms the karez into an underground reservoir, similar to a dam but even better, because the underground reservoir does not evaporate or seep out,” Samani said.

Samani’s innovation has implications for more effective and sustainable irrigation wherever karezes are used. He also believes that the knowledge gained through his karez experience will have applications to irrigation in New Mexico and other Southwestern states where the climate and terrain are similar to Afghanistan’s.

Although there were a few bumps in the road, the 11 specific irrigation projects that Samani supervised in Herat were completed over the course of about five months for approximately $1 million. The rehabilitated irrigation infrastructure has allowed for the addition of about 20,000 acres of irrigated farmland, providing approximately 124,500 new agriculture-related jobs and improving the prosperity of 33 villages.

Jim Libbin, an associate dean in NMSU’s College of Agricultural, Consumer and Environmental Sciences and AWATT’s U.S.-based director, affirmed the “critical importance” of Samani’s work in Herat Province, an area where both U.S. and Afghan government entities have encountered difficulties.

“Dr. Samani addressed a local need, saving lives of those who undertake the annual repairs, enhancing the economic sustainability of the local and regional economy, building incomes and providing food for a people who live well below the poverty line and caloric intake standards,” he said. He added that the Afghans will be able to apply what they have learned from Samani’s approach as they move on to “the many remaining karez systems that beg for restoration work.”

AWATT’s tangible long-term benefits for agriculture and the environment have drawn praise from high officials in both the coalition leadership and the Afghan government. Its effectiveness has been noted at the local level, as well. In an appreciative note to Samani, a village leader in Shindand said, “Nobody has ever helped us. First the Russians came, then the Mujahedeen came, then the Taliban came. They all made promises, but nobody helped us. You are the first one who has helped us. May God reward you a hundred times. Our gratitude is the size of these mountains.”
April 11,2011

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