Lake Chapala is Mexico’s largest natural lake. On the geological timescale of millions of years, all lakes are temporary features on the earth’s surface. Once formed, natural processes begin to fill them in and/or to drain them.
Lake Chapala resulted from drastic earth movements, accompanied by earthquakes and faulting which occurred some twelve million years ago. Lake Chapala collected on the floor of a rift valley. Movements along the parallel systems of faults that caused the rift valley still occur today. Evidence for this continued movement can be seen in the cracked or displaced walls of some local buildings.
Given its advanced age, it is not surprising to discover that Lake Chapala was once (thousands of years ago) much larger. In fact, though no-one has so far proven it beyond doubt, it may have been immensely large, covering an area seven times its present area, with a correspondingly long shoreline. At a later stage in its history, it became the deepest lake of an interconnected series of lakes which flooded the valley floors where the towns of Jocotepec, Zapotitan, Zacoalco and Sayula are today. The present Lake Chapala is thus probably only a small remnant of the original version.
The lake is under heavier pressure than at any time in its existence. Local towns and the nearby city of Guadalajara see it as an inexhaustible supply of domestic and industrial water. Tourists see it as a recreation resource, and the thousands of foreign retirees who have settled on its shores see it as a major reason for the area’s beneficial climate.
A case study of ‘residential tourism’ in the villages on the northern shore of Lake Chapala is discussed in chapter19 of Geo-Mexico: the geography and dynamics of modern Mexico.
The levels of flow of the River Lerma, the only river of any size entering the lake, are crucial to the health of the lake. In recent years, demands for Lerma water have multiplied many times over, principally for farms in neighboring states, but also for industries. All the other rivers entering the lake are much smaller and, with rare exception, flow into the lake only a few times a year during the rainy season. The hydrology of Lake Chapala is discussed in chapters 6 and 7 of Geo-Mexico: the geography and dynamics of modern Mexico.
The good news is that Lake Chapala was recently declared an Internationally Important Wetland by the Ramsar Convention, joining a large global network of similarly important wetland sites. The 13th International Living Lakes Conference is being held in Chapala, March 22-25, 2010.
This is an edited excerpt from Tony Burton’s Western Mexico, A Traveller’s Treasury (4th edition) .