As part of the mundane annual survival script in Africa's semiarid Sahel, 13 Bambara peasant families in this villiage's farming cooperative have for years dug by hand 90-foot-deep wells during the six-month dry season. The wells provide the life-creating ground water, which they hand sprinkle over their vegetable farm.

The wells dug last fall, laboriously refilled at the beginning of each spring's rainy season, will not have to be shoveled out again at the start of this year's dry season in October. the families' 11-acre field will be expanded to a 17-acre communally cultivated and irrigated farm that officials hope will more than double individual incomes -- from $112 a year to an incredible $300.

In Mali, where the annual per capita income is $96, the hoped-for success of Kati's just completed small-scale irrigation scheme represents a leap into affluence and food abudance for the 80 members of the farming cooperative.

Yet the small irriagation scheme at Kati provides a glimpse of the difficult and expensive problems development experts encounter in trying to help the Sahel countries feed their growing populations.

What started out as a simple two-year project to expand Kati's farming cooperative vegetable farm to 17 acres through irrigation ended up taking five years to complete. The cost grew from an original estimate of $8,000 to an actual outlay of $40,000, or $6,450 for each of the six new acres.

Since the calamitous 1968-1974 Sahel drought, the eight West African countries that fall into the belt running along the southern edge of the Sahara, such as Mali, have been in a race to raise their food producting levels to match an average 3 percent annual population growth rate that has already outstripped most of the region's ability to feed itself.

Until recently, huge, costly irrigation projects were considered a solution for the Sahel's chronic food problems, but studies indicate that both the initial costs and the prohibitively high maintenance expenses of large irrigated projects do not augur well for widespread use in the poor Sahel countries. Small projects like Kati's although expensive to build, may be on a scale that peasants can afford to maintain, development experts said.

Of almoat $2 billion that has been poured into the Sahel for food development projects since 1975, 10 percent went into irrigation projects. During the same period, however, the number of acres under irrigation in the Sahal fell from a high of 574,000 acres to 560,000.

The figures indicate that the number of new irrigation projects is just barely ahead of the pace at which other recently completed projects are being abandoned because neither the peasants nor their governments have the money to maintain them. The costs of these projects, particularly for landlocked countries such as Mali, continue to rise while the rate of completion is frustratingly slow. Of 91,000 acres that were planned to be completely irrigated in Mail by now, for example, 17 percent, or 15,000 acres, have been completed.

The Kati project was taken on by Africare, a Washington-based nonprofit development organization.

Funded by the U.S. Agency for International Development, private foundations, churches, business corporations and wealthy individuals, Africare administers moderate-sized projects that African governments have planned but do not have the funds to carry out, according to the organization's director in Mali, Richard J. Benn.

Benn, 32, came to Mali as Africare's director in 1975 after spending four years as a Peace Corps volunteer in neighboring Niger working as a well-digger and English teacher.

"I guess I've been exposed to all the difficulties and problems that get in the way of development efforts," he said. "The problems don't change, they just repeat themselves and you just work at overcoming them," he added.

In early 1976, Benn went to the Malian Ministry of Rural Develpment, where officials suggested that Africare take on the Kati project. After discussions with Kati's farming cooperative and the village's mayor, Benn submitted a proposal, together with the ministry's original $8,000 cost estimate to Africare's Washington office.

"It met Africare's standards," Benn said, "wasn't highly technical, was appealing from the standpoint of low-cost financing and would directly benefit the local community from improved food availability to the income they would earn from selling vegetables in Bamako," Mali's capital 10 miles west of here.

A second look at the cost estimate showed it was too low. Government planners had left out the drilling costs of five bore-hole wells, hoses, pipes, wiring, electrical equipment and a shed to house the diesal generator. The cost climbed to $11,000.

Africare then approached the Scheide Fund in New York. Six months later the organization agreed to fund the project. Further study showed, however, that the configuration of the land would require seven wells, not five, and that the drilling expenses would be much higher than originally estimated because of the rising cost of fuel, which is trucked long distances overland into Mali.

In February 1977, a year after Benn had originally approached the Development Ministry, Africare went back to the officials of the Scheide Fund to tell them that because of revised plans, fuel costs and Mali's 25 percent annual inflation rate, the cost of the project had risen to $34,000. The Scheide officials agreed to meet the higher costs and Africare was able to sign a contract with the Malian government in the summer of 1977.

A Malian company that was selected through a lengthy contract bid system drilled the seven well holes before the end of the year. But when Benn tried to install the pipes he discovered that the circumference of the bore holes was too small. The company, which by then had moved on to other projects, refused to drill again. Government drilling teams, who are on a tight year-round schedule, finally rescued the project by drilling new holes in March 1980.

Then Benn ordered the pumps from France, which arrived with essential parts missing. An electrical company, advanced money to install the pumps, went bankrupt while Benn was waiting for the reordered parts. An out-of-work electrician agreed to do the work, but he was unable to proceed immediately since "half the material for the wells" had been stolen from the idle well sites in the intervening months, Benn said.

Kati's city council voted to provide $6,000 to replace the stolen materials and provided free labor to help the electrician install the pumps. All seven finally in place in the first week of April this year, but it was too late for the cooperative to use them since the dry season was almost over.

The field is now being prepared and the hand-dug wells refilled possibly for the last time, for the June-September rainy-season crops of millet and sorghum. After the October harvest, Kati's farming cooperative will once again turn to vegetable farming, using the well pumps for the first time.

"The Kati project was an exception," said Benn. "Similar projects are usually extended by an extra year by delays," he added.

A former Boston social worker, Benn said that during his 10 years of working on Sahel development efforts he has been angered to the point of quitting only once. While struggling to complete another irrigation project in the Malian town of Goudam, 450 miles northeast of Bamako, Benn had put the necessary pumps on a river boat, had driven three days on a dirt road to reach the town overland and, when the boat arrived, discovered that the pumps had been left in Bamako after a merchant bribed the boatmen to take his sacks of rice instead.

"But you forget about these incidents later when you see the food growing where there was none before," Benn added. "For all [the projects'] cost in anger, frustration and money, the joy comes at the end when you see wheat, beets, onions and cabbages where before there was only dust."