In the year 1534 when Cabeza de Vaca escaped from the aborigines of southern Texas by whom he had been enslaved for six years, he made his way on foot from the vicinity of Galveston to the west coast of Mexico. Although his Relación was not printed until 1542, the verbal report of Cabeza de Vaca gave impetus to the growing interest in exploration of New Spain. Estevanico, the black, one of de Vaca's companions, served as guide to Fray Marcos de Niza on the first Spanish reconnaissance to reach the village of Zuni in New Mexico.

The earliest Spanish exploring parties hoped to find riches, but expected to acquire, at the least, facts. These "gentlemen of high quality," as Castaneda called them, wanted to see for themselves whether the cities of Cibola had streets of silver. Hearsay was not enough. Rumor was to be replaced by first-hand knowledge.

Without discounting the hope for personal gain, these men presumably were fired with some further intellectual and spiritual motivation, among which must have been the desire for facts about these parts where we are assembled. Inscription Rock, only a few miles west of Albuquerque, bears illuminating tidbits of history. Don Diego de Vargas, says the carved inscription of 1692, came here "A su costa"—at his own expense.

We are attempting to survey and correlate some of the facts which people have gained about the nature of semi-arid lands. We are better off than the early Spanish explorers, for in the intervening period data and information have been accumulated in scope and in detail beyond the imagination of our predecessors. We have available excellent maps, knowledge of the soils and of the rocks, both at the surface and below the ground, measurements of precipitation, descriptions of the vegetation, data on the flow of streams, experience in the use, if not the husbandry, of the land.

It is true that for the purposes of our complex civilization, the need for additional data has far outstripped the programs of fact-finding. But it appears that an indefinite expansion of the collection of routine measurements would still leave something lacking. I draw the distinction between measurement data and understanding; between the collection of facts and knowledge of processes and interrelationships. Although we have a wealth of data, our understanding of the semi-arid environment is poor.

Understanding the physical and biologic processes operating in an environment is important for living in and with the land. As an example, let us look briefly at the interrelation of the water and sediment in ephemeral streams, and the problem of valley trenching or arroyo cutting.