ALL ABOUT THE ENVIRONMENT
By Dr. Todd Stong
Water Supply Around the Lake
Lake Chapala water was the primary source of life for pre-historic area communities. Mezcala and San Juan Cosala are examples of such that have existed perhaps for 1000s of years as ruins further up the mountain attest when the lake was as much as 600 feet higher. Year around, pure water flowing mountain springs are yet found today about the base of Cerro Viejo, just north of Jocotepec. These served villages since ancient times as artifacts and even a pyramid (perhaps 1500 BC) on that mountain suggest. The village of Potrerillos just in the last few years traded its spring water mountain pipeline for a government drilled deep well.
Nearby Huejotitan and Trojes in the past also depended on these mountain springs that provided pure water under the force of gravity. Springs remain the most prized source for water about the world for small communities. The potential exists today for these humble villages to secure significant income from bottling this special spring water for sale to the area as an alternative to bottled water now sold which almost always originates from the lake.
In time villages about the lake hand dug large wells to serve whole communities. One such large well yet exists at the east end of Roca Azul. These wells might be 20-30 ft in diameter and up to 50 ft. deep. Individual homes more distant from the village well also hand dug wells which are found in many back yards about the lake even today.
These are often 3-6 feet in diameter and up to 30 feet deep. In all cases the water from these shallow wells comes from the lake via intervening soils which assure it is well filtered and thus quite clear. However, the use of water from these wells today would require in most cases treatment via a UV light or with chlorine (2 teaspoons of common bleach per 55 gallons) to kill bacteria.
In the last 30-50 years as populations have increased the government, not wishing to purify water from the lake or from shallow wells, moved to drill deep wells that would seek the rain water that infiltrated the nearby mountains. Well drilling is both costly, $50,000 for a private lot to $100,000 for a village well, and risky for no one really knows where water may flow beneath the ground. In the Western World where engineers seek the most cost effective solution for water over 80% of the time it is taken from lakes and rivers.
Deep well based water supply about the lake generally aims for the following levels of supply: 25 gal/person/day in villages of less than 1500 people, 50 gallons for villages up to 15,000 and 75 gallons for towns over 15,000 persons. All but the largest villages pump water to hillside tanks (depositos) about 2-3 times/day and that water then runs down to various sections of a village as the water man adjusts pipeline valves.
Some areas may only see water delivery a few days a week. Accordingly most homes on the north shore have ground tanks (aljibes) of 500-1500 gallon capacity from which each home pumps water to a roof tank (tinaco) to provide water pressure in the home.
Water from deep wells is almost always free of bacteria but in some areas it may contain excess amounts of minerals. For example nearly all wells in Chapala have excess arsenic. In that poorly placed pipelines in the streets offer the chance of contamination it is never certain water will reach a home bacteria-free. Thus, for drinking it is advisable to treat with a UV light or to chlorinate.
In larger towns the government pumps some water directly into its pipelines from the wells rather than sending to a hillside storage tank. In these cases the water may contain some sand which will normally settle out if it had gone to a hillside tank first or to a home underground tank. Thus, as a precaution it is advisable in such villages to add a set of particle filters (100 micro and a 5 or 10 micro). If there are objectionable minerals in the water, perhaps in 10% of the wells, it is necessary to also incorporate a reverse osmosis system. If one wishes greater water pressure than provided by a roof tank they need also to add a pump between their ground tank and a pressure tank.
For more information about Lake Chapala visit: www.chapala.com