The city of Guadalajara has relied on Lake Chapala as a principal source of water since the 1950s. Shortly after, a few consecutive years of poor rainfall dramatically decreased the water level of the Lake. The level rebounded until 1979, when Lake Chapala’s water level began rapidly decreasing due to increases in urban water consumption. Erosion due to deforestation along the Lake as well as the Lerma River has led to increased sedimentation of the Lake, also contributing to loss of lake depth. The shrinking depth has also raised the Lake’s average temperature, resulting in increased evaporation.
Simultaneously, the waters of Lake Chapala are polluted by municipal, industrial and agricultural wastes, coming primarily from the Lerma River. The increased presence of nutrients from the pollution combined with the warmer water has been a boon to an invasive species of water hyacinth. The increase in water pollution has had devastating effects on the ecology of the lake. Fish stock has decreased dramatically and some endemic species (e.g. certain Chirostoma) are on the verge of extinction. Contaminated fish stock has also posed a serious threat to the health and livelihoods of people who depend on the fish for food and their livelihoods.
The drop in the lake’s water level has uncovered political issues that had been hidden for many years. Its fast decay has raised concern in the surrounding areas and in the scientific community. It was the Global Nature Fund’s “Threatened Lake of the Year” in 2004. By 2007 and 2008, the level of Lake Chapala increased drastically, though the levels have yet to surpass the level in 1979, when the levels began a precipitous decline. Although it is still subject to agricultural, domestic, and industrial sources of contamination, the actual levels of hazardous materials has not been officially assessed with regularity.
Although water level and quality improved due to water treatment plants along the Lerma river, in 2017 the water quality of Lake Chapala water was assessed as a risk to public health. In 2018, the Lake Chapala water level is at 81.68% of capacity, up from 66.66% in 2017 primarily because of increased rainfall this year.
Improvements have been made in the quality of the lake water with the most recent detailed study pronouncing the lake safe. Testing of the water at Lake Chapala, for recreational safety, found a coliform count of 50. To help put this in perspective, at a US public beach, the water is declared safe to swim in if the coliform count is under 126.
Another issue with the lake is the invasive, non-native hyacinth plants. Removal of the non-native water hyacinth plant has been tried unsuccessfully in the past but the Jalisco state government has not given up. A year-long, 4-million-peso project is now getting under way to remove the invasive species, currently estimated to cover about 3% of the lake’s 114,000-hectare surface
Mexico’s new President, commonly referred to as AMLO, has decreed that Guadalajara will not be permitted to draw any more water from Lake Chapala, although he has not stated where their water is not going to come from. The President has also commented on turning the Lake Chapala area into a tourist destination.