 Major low-water periods are estimated to have occurred about 1.6 to 1.0–0.57 million years ago (where it might have dried out completely), 420,000 to 250,000–110,000 years ago, about 25,000 years ago and 18,000–10,700 years ago.During the peak of the low-water period between 1390 and 1860 AD, it may have been below current water levels.The lake's water is alkaline (pH 7.7–8.6) and warm with a typical surface temperature between , while deep sections typically are about .