The size of pluvial lakes, such as Lake Manly, is governed by the balance between inflow by precipitation or rivers or streams and evaporation, if one assumes that seepage and overflow are not important. This can make the surface of such lakes a useful gauge for paleoclimatic conditions. The principal water supplies to Lake Manly were the Amargosa River, the Mojave River and the Owens River, which yielded a large integrated drainage system over the southwestern Great Basin. The total surface area of Lake Manly's catchment was about . Contrary to what early researchers first speculated it is however likely, that the three rivers never reached Lake Manly simultaneously. The principal river flowing into Lake Manly was the Amargosa River. It originally ended in Lake Tecopa; only more recently than 600,000 years ago did it arrive at Death Valley, possibly as recently as 140,000 to 18,000 years ago. Even earlier, the Amargosa River may have flowed towards the Colorado River. The Mojave River may have reached the Amargosa and thus drained into Lake Manly, but probably only during wet periods, and only since the most recent Pleistocene; the breaching of the intermediary lakes Lake Manix, Lake Mojave, and Lake Dumont occurred later than 18,000 years before present, and earlier overflow is uncertain. Before the time where it flowed into these lakes, the Mojave River drained westward. Overflow from Lake Mojave may have continued until 8,000 years ago. The Mojave River reached the Amargosa through Silurian Valley and Salt Creek; on its way it crossed Dry Lake, Silurian Lake and another pond at the foot of the Salt Spring Hills. Currently, the integration of the Mojave River into Death Valley is nearly complete; once the basin of Lake Mojave has been filled completely with sediment to the altitude of its own spillway, even under current conditions its waters will reach Death Valley. At least during the Tahoe glaciation, the Owens River drained into Lake Manly after filling Owens Lake, China Lake, Searles Lake and the Panamint Valley. This river system formed 3.2 million years ago when lava flows blocked a channel that had previously drained the Owens River across the Sierra Nevada. Sediment data indicate that 900,000–800,000 and 700,000–600,000 years ago waters from Panamint Valley reached Lake Manly, as chloride was being removed from the valley at that time.