The combination of those features defined by Wittfogel (1967: 30-61) as part of his model of a compact simple or semi-complex Mesoamerican hydraulic system were present at Casas Grandes during its Medio Period. These included such productive hydraulic installations as canals, aqueducts, reservoirs, and sluices, as well as specific up-slope protective devices as check dams and terraces. Apparently, this entire socio-economic mechanism was brought north to Paquime in the mid-11th Century by a few donor traders of puchteca, as described by Sahagun (Dibble and Anderson, 1959). These folk, in a span of a few years, thrust an urban economy of social and environmental exploitation upon the backward, indigenous groups of soil members and parasites. This frontier culture conquest situation (Foster, 1960: 10-20) created a local hybrid horizon which, during its pioneer phase, was extremely virile and responsive to the necessity of adopting new food chains to serve its expanding needs. Through the course of 300 years, hundreds of satellite farming communities sprang up in the bottomlands to support the growing urban population of the central city, which drew more and more people from the soil and set them to non-food producing tasks-as members of artisan guilds, or in various extracting and processing industries, domestic and foreign trade, and large construction works (Wittfogel, 1967: 243-47). In all probability, these leaders were members of the powerfUl religion of the plumed serpent (Quetzalcoatl). It is apparent that in this burst of economic energy, the population grew to fill the lush valley lands and then, at least by A.D. 1150 (Scott, 1966: 42 and 60), more satellite villages were built to the westward, up the mountain slopes, to the upper limit of agriculture which was frost-free for only three months of the year. Whoever controlled the people during this period of growth prevailed upon the indigenous labor pool-either by slavery, corvee contract, or a combination of both-to instigate a surface water-soil conservation system which proved to be an amazing piece of prehistoric engineering. Many students, such as Bandelier (1892), Lumholtz (1902, Vol. 1), Leopold (1937 and 1949), Brand (1943), Withers (1963), and Herold (1965), as well as Howard and Griffiths (1966), have remarked on this, and some, such as Herold (1915), Withers (1963), and Luebben (1969), have intimately studied portions of the elaborate protective aspects in the Casas Grandes Archaeological Zone, which Wittfogel (in Thomas, 1956: 159-60 and 1967: 3, 24-25) would define as a required part of his hydraulic model.
Archaeological reconnaisance has revealed that pre-Hispanic mountain-slope agriculture was practiced, wherever feasible, in conjunction with a conservation program which involved five mountainous areas. All of these contained evidence of the presence of Casas Grandes material culture and were thought of as a homogepous archaeological zone. Two-the Santa Maria and the Carmen valleys-parallel and lie east of the Casas Grandes heartland. These have different watersheds, which, as yet, have not been intensively studied, and therefore were not considered in this paper. Surveys to the west of Paquime revealed that protective devices were placed in two watersheds west of the continental divide, as well as in the Casas Grandes drainage on the east slopes of the Sierra Madre. The former two are part of the great Yaqui river system. One included the headwaters of the Bavispe of the East, which drained the mountains north of the Las Cuevas district, herein referred to as the Tres Rios area. This other lies to the south and emptied into the Papogochic, and is called the Garabato-Chico. Together these three mountain regions cover some 23,000 sq. km. and extend north from the 29 0 40′ north latitude to the international border, a distance of 230 km , and 100 km. east of the 1080 55′ west longitude, or roughly from Nacori Chico, in Sonora, to the eastern flanks of the Sierra Madre, in Chihuahua. The Cases Grandes shed includes a little better than half of this entire area, or some 12,000 sq. km. of land. This part of the drainage was modified to safeguard some 80,000 hectares of rich bottomland.
The following data, pertaining to the upslope terrace or trinchera stone devices, were collected by Herold (1965), mainly from the Rio Gavilan portion of the area, lying west of the divide, but can be applied in general to the Casas Grandes drainage as well. The pre-Spanish engineers first placed linear borders on the “top-of-themountain” terrain (Woodbury, 1961: 12-13 and Herold, 1965: 106-07) in elevations between 1,524 m. and 2,438 m. above M.S.L. These simple, single to three-tiered stone rows followed the natural contours of the land and were placed on slopes which dropped at an angle of 1° to 30. They were irregularly set from 6.10 m to 65.85 m. These plain devices so slowed down the periodic torrential surface runoffs that the disastrous effect of sheet flooding, which tends to eradicate the mountain soils, was minimized.
On lower slopes, which dipped from 30 to 100, the engineers strategically-placed series of terraces. These were more substantial than linear borders, but they too paralleled the natural contours. These were purposefully built as hillside steps and varied from .61 m. to 1.22 m. in height. They were constructed anywhere from 6.10 m. to 30.35 m apart, dependent upon the angle of the slope and the height of the retaining walls which were designed not only to slow the surface water runoff, but also to collect mantle by the simple expediency of natural deposition caused by checking-rather than by impounding-water flow.
On the steeper portions of the upslope areas, in arroyo cuts with gradients of up to 300 , the people of Paquime placed check damsanother type of stone retaining walls which were not unlike the slope terraces, but ran at right angles to the arroyo bed. These devices made up some 84% of the total system (Herold, 1965: 103) and varied tremendously in number, dependent on the length and grade of the arroyo cut. They ranged in height from .09 m. to 3.75 m. and were so set that the top of one was level with the base of the next upslope wall. Soil was naturally deposited behind these walls, and, as a consequence, they often had to be raised. Conceivably, the check dams could be built up to the point where they would completely fill their arroyos (Ibid: 119-22, fig. 18), as has been noted farther south in Mexico (Sanders, 1965: 43) Often, these check dams were staggered to force the rainwater to run down slope in a zigzag course, thus slowing it further (Withers, 1963).
In the permanent flow of the upslope areas, the prehistoric hydrographers – imitating the beaver – placed riverside terraces (Ibid, and Herold, 1965: 109, pIs. 11-12) or dams across the main arteries. These were found to measure from 3.05 m. to 12.19 m. in length and were spaced from 18.29 m. to 62.48 m. apart. This system and its parts were repeated wherever necessary to control the violence of the thunderstorms throughout the down slope portions of the valley until the waters reached the rich bottomlands. Here a series of irrigation canals were built, crisscrossing the valley, thus permitting widespread hydraulic farming The entire system was so effective that the people fearlessly founded a number of their satellite farming villages on the valley flood plain. There is increasing evidence that linear and grid borders, check dams, and terraces were used by a number of prehistoric occupants of the southwestern portion of the United States (Woodbury, 1961: 35-34). In this area, they have been termed “agricultural field systems” (Ibid: 8-34) because of their limited extent and scattered geographical distribution. These, because of their localized character, should not be confused with the expensive regional design of Casas Grandes, as has been done by Howard and Griffiths (1966: 81). Withers (1963) recorded that, “it is generally conceded by contemporary inhabitants and users of ‘the mountain’ that these dams are the principal conservation force holding the mountain together today.”
All in all, the archeological evidence indicates that the soil exploiters of Casas Grandes, in the words of Leopold (1949: 150) were “capable of inhabiting a river without disrupting the harmony of its life.”