Lake level change

Near the end of the period in which the Lower Houses were occupied, around 450 B.C., a very dramatic environmental event took place in the Southern Titicaca Basin. For reasons that are not entirely clear, the level of the lake dropped to about 16 meters below its modern level. This is the third low stand of Lago Wiñaymarka identified by Abbot and colleagues during the late Holocene ([Abbott et al. 1997a]: 179, also Figure 4; low and high lake stands are indicated also in the right-hand column of Figure 2.4). Using data from multiple cores of lake bottom sediment, they have determined that the lake during this approximately 200 year period (450-250 B.C.) was 10-12 meters below overflow level, equivalent to 16-18 meters below the average modern lake level of 3810 m.a.s.l. This is probably related to a prolonged drought, though factors other than reduced rainfall could produce extreme lake level fluctuations.

At any rate, the effects of this event were dramatic. Since the southern part of Lake Titicaca - Lago Wiñaymarka or the little lake - is very shallow - almost all of it is less than 20 meters deep - it became almost completely dry at this time. The lake that the visitor sees today did not exist. In its place was an immense grassy plain, crossed by small, meandering rivers and dotted with marshes.

Figure 6.7 shows the reconstructed shorelines of Lago Wiñaymarka for its minimum and maximum depths during the late Early Formative (Middle Chiripa) and the early Middle Formative Periods. The basic outlines of the lake were approximately those of today (the modern shoreline is indicated on the figure by a dotted line). Figure 6.8, however, shows the lake's reconstructed upper and lower shorelines during the latter two centuries of the Middle Formative. At this time Lago Wiñaymarka was reduced to two small lakes, one near the modern town of Yunguyu, and the other - still connected to the Lago Mayor, since the Straits of Tiquina were not dry - near the Bolivian town of Achacachi.

Figure 6.7: Reconstructed shoreline of Lago Wiñaymarka, 1000 B.C.- 450 B.C.

Figure 6.8: Reconstructed shoreline of Lago Wiñaymarka, 450 B.C.- 250 B.C.

The drying of the lake had three immediate effects on the local economy, apart from the obvious agricultural effects of what may have been a severe drought:

1. Opportunities for fishing were greatly reduced. Although people still ate fish, they either had to trade for them or had to travel quite substantial distances to fish in waters which were much reduced in extent and certainly also in yield.
2. Vast new grazing lands were created, allowing for an increase in llama and alpaca herding.
3. The possibility was created for llama caravan commerce directly between the Taraco Peninsula and the western side of the Basin. Since the little lake was mostly dry, it was possible to walk directly from Chiripa to the Yunguyu area (see Figure 6.8), and from there to the important population centers to the south of modern Puno.

It seems clear the the inhabitants of the Taraco Peninsula at this time were forced to shift the focus of their subsistence activities. We may suppose that the importance of fishing and lacustrine collecting was greatly reduced, while herding and agriculture were intensified to compensate. This assertion has yet to be demonstrated archaeologically. It is a reasonable supposition given the drop in the lake level and concomitant contraction of the shoreline of Lake Wiñaymarka (see Figure 6.8). Further research is needed to verify this scenario, however.

It is probable, then, that as agriculture was rapidly intensified - this shift may have taken place over the course of a few decades or even less - fallow cycles were shortened and new land, previously unworked, was brought under cultivation ([Boserup 1965]). This shift in emphasis of the subsistence economy was undoubtedly a very significant event. Equally significant, however, was the simultaneous expansion of trade relations within the Titicaca Basin, and the increasing importance of the Taraco Peninsula communities within them.