In statistical theory, covariance is a measure of how much two random variables change together. In other words, covariance is a measure of the strength of the correlation between two random variables. Also, it can be considered as a generalization of the concept of variance of two random variables.
Facts & Figures. Lake Baikal is the largest freshwater lake by volume (23,600km3), containing 20% of the world's fresh water. At 1,637m, it is the deepest freshwater lake in the world; the average depth is 758m. It is 636km long and 81km wide; the surface area is 31,494km2. The lake is estimated to be 25 million years old, making it one of the most ancient lakes in geological history.
1 The largest freshwater lake of South America is Lake Titicaca, which is also the highest body of water on Earth at 3,821 m (12,507 ft) above sea level where boats can travel.  The largest lake in the world by area is the Caspian Sea, with 394,299 kmÂ².