The article is aimed at showing the human economic activities in the valleys of Amazonian rivers as well as its specific relationship to the natural enviroment of the region that can be described in terms of harmonic connection rather then dependency or subordination. In the first part of the article the main features of the environment of the river valleys are described. Against a background of the geologieal structure the author shows the abundance of forms of fluvial configurations and the corresponding vegetation diversity. He stresses also the fertility and productivity of the local alluvial soils. The houses of the farmers (ribereños) and their fields are situated in the diversified environment of valleys, close to the rivers. They are located on the different alluvial levels characterized, as a result of variation of the water level, by different duration of the period of accessibility between floods. The adequate assessment of the elevation of the fields as well as the proper selection of the cultivated species (and varieties) so their vegetation cycle is no longer then the accessibility period - different on different levels, is the essential condition of the prosperity of cultivations in such an environment. The good knowledge of the environment permits the nearly optimum use of its advantages, and that without disrupting the valley's ecosystem. The fiel dwork calendar provides a synthetic representation of the human economic behavior in this kind of milieu environment. It shows the rhythm of farm work against the background of the seasonal changes of the natural conditions, result of variations of the water level in the river. The concordance of both rhythms can he treated as the manifestation of harmony between human beings and their environment.