Lake level change

The beginning of the LF1 coincided with a dramatic rise in the level of Lago Wiñaymarka. In the latter part of the Middle Formative, as discussed in Chapter 6, the level of the lake was 10-12 meters below its overflow level, or 16-18 meters below its modern average of 3810 m.a.s.l. (Figure 6.8). Around 250 B.C., however, at the beginning of the LF1, the lake level rose abruptly to approximately 1-7 m below its modern level, and remained in this range for the next 350 years or so ([Abbott et al. 1997a]: 179 and Figure 4). The reconstructed shoreline for Lago Wiñaymarka at these levels is presented in Figure 7.5.

Figure 7.5: Reconstructed shoreline of Lago Wiñaymarka, 250 B.C.- 150 A.D.

Around 100 A.D., late in the LF1, the lake level fell again to the same level as in the later MF (illustrated in Figure 6.8). This low stand, the fourth in Abbott et. al.'s sequence ([Abbott et al. 1997a]: 179), lasted only about 200 years. At the end of this period, around 300 A.D., the lake level rose again, this time to modern levels or even slightly above. Lake levels remained at this level throughout the LF2 and Tiwanaku Periods.

Thus, there were three main periods within the Late Formative from the standpoint of lake levels.

1. Lake levels were relatively high (3803-3809 m.a.s.l.) from 250 B.C. to A.D. 100. This represents the earlier portion of the LF1 period.
2. In the last two centuries of the LF1 (100-300 A.D.), lake levels dropped precipitously, to 3792-3794 m.a.s.l.
3. Throughout the LF2 (300-500 A.D.) lake levels were higher, remaining above the overflow level of the Desaguadero River and perhaps surpassing the modern average (indicated by the dotted line on Figure 7.5). The probable range for this period is 3804-3811 m.a.s.l. ([Abbott et al. 1997a], Figure 4).

Perhaps more to the point, there were three principal changes in lake level:

1. A sharp rise ca. 250 B.C. (beginning of the LF1)
2. A sharp drop ca. 100 A.D. (middle of the LF1)
3. A sharp rise ca. 300 A.D. (LF1/LF2 transition)

As I pointed out in my discussion of the Middle Formative (Chapter 6), it is an interesting fact of southern Titicaca Basin prehistory that rises in lake level appear on the whole to be more disruptive to local social systems than do drops in lake level. This generalization certainly holds true in the case of the LF. The two rises in lake level correlate with significant changes in material culture and settlement. The first (250 B.C.) corresponds to the transition from the MF to the LF1, and the second (300 A.D.) to the LF1 to LF2 transition. The sharp decline in lake level around 100 A.D., on the other hand, does not seem to be related to any significant cultural or social changes, at least not that I can distinguish at this time.