Where Drinking Water Comes From

Drinking water comes from the same places as all other water, it just tends to get treated differently to become potable supply. Treatment is required if specific source water conditions are not met. The risks from even natural sources of contamination (e.g., birds, wildlife, erosion) are substantial enough to necessitate treatment in most cases. Yet there is general recognition that drinking water sources need protection, even if that protection is not always provided. A study by the Nature Conservancy revealed that on average about 37% of the land in drinking water supply watersheds is protected from human–derived contamination sources. The other 63% is mostly in private ownership with varying degrees of development (8% on average) and agriculture (15% on average). There is geographic variation, with water supplies for west coast cities having a greater proportion of protected land than for eastern cities, and with northern New England having less developed lands but more agriculture than southern New England. Each case is to some extent unique, leading to differences in the level of treatment necessary.

About 85% of the population of the USA gets its water from public supplies, a percentage that has increased over decades from around 70%. About two thirds of that water is surface supply, a value that has been declining for years from a high of about three quarters. The remainder of the potable supply comes from wells, which have increased in use over the years. This is interesting in that public water supplies are fairly tightly controlled by law and regulation, and many wells are part of public supplies, but private well supplies experience minimal regulatory control. This suggests that an increasing portion of the population is less protected against water quality threats, although it is also true that water from wells is usually of acceptable quality.

About a decade ago 77% of surveyed people did not know where their drinking water came from. That is a scary statistic that suggests a low level of interest in this critical resource. Such lack of knowledge, and presumably concern, is very disappointing but is also consistent with the limited public support for water resource management. Education may not turn everyone into cooperating supporters of better land and water management, but it is a safe assumption that we won’t get more enlightened policy or greater support without such education.