Lake Chapala South of Guadalajara, Mexico20.2N 103W
Lake Chapala is the largest natural lake in Mexico, located 42 km south of the metropolitan area of Guadalajara (both visible in the upper left quadrant). Hydrologically, it belongs to the Rio Lerma Lago de Chapala Rio Santiago drainage system, one of the most important in Mexico. The main tributary, the Lerma River, supplies almost half of the water input, while the Santiago River drains the lake water to the Pacific Ocean.
The catchment area is large as compared with the lake area, amounting to 52,500 km2. Sixteen percent of this area drains directly into the lake via small streams and runoff, while the remainder belongs to the watershed of the Lerma River. The climate is moderate, tropical and sub-humid with a single summer rainy season. Winter rains are less than 5% of the annual precipitation. Average annual evaporation (1,910 mm) greatly exceeds annual precipitation (781 mm in average). Principal uses of the lake are irrigation, tourism, recreation and fisheries. In addition, it is the main water source for Guadalajara City with a population in excess of 4.5 million, whose water demands are increasing at a rate of 4% per year owing to urban, agricultural and industrial development.