Yemen is by far the most fertile part of the Arabian peninsula, yet agriculture is a hard scrabble. There are two major regions: the smaller coastal region or Tihama and the more extensive mountainous highlands. The Tihama is a narrow, hot, humid semi-, desert, almost waterless an strip that extends the entire seacoast from Maydi on the northern frontier Saudi Arabia to the Bab al Mandab at with the country's southern limits and occupies approximately 10% of the country. These 20,300 sq. Km. miles are watered principally by seven major wadis carrying runoff from the highlands. Their waters...