About half of the world’s population uses groundwater for drinking water (Margat and van der Gun, 2013), but how much of that comes from domestic wells? Unfortunately, the amount is not precisely known because accurate information about domestic well use is not available for all counties, including some counties with large populations such as China. However, the available information indicates that hundreds of millions of people worldwide rely on domestic wells. Sutton (2021) estimated that more than one billion people around the world use self-supplied water (i.e., households providing water by their own means). This estimate is for all types of household self-supplies, including those using surface water sources and rainwater cisterns, but the majority of self-supplies are from groundwater sources.
Domestic wells are used in both urban and rural areas, although they are used more in rural areas where approximately 45 percent of the world’s population lives (United Nations, 2018). A study of self-supplied drinking water across the Asia-Pacific region concluded that household self-supplies, of which groundwater is the dominant source, accounted for 20 percent of urban water supplies and 37 percent of rural water supplies (Foster et al., 2021).
Table 1 shows information on domestic well use from a selection of countries. In Canada, 4.2 million people (11 percent of the population) use domestic wells and in the United States, 42 million people (13 percent of the population) use domestic wells. Although the total number of domestic wells in United States continues to increase, the percentage of the population relying on domestic wells is declining as the population shifts to urban centers where public water supplies are available. In densely populated European countries (e.g., England, Germany), domestic wells are used by less than 1 percent of the population.
It is difficult to find information about domestic well use in developing countries. New data have been published recently (e.g., Sutton and Butterworth, 2021; Foster et al., 2021) because household self-supply is being promoted as an approach to meet the United Nations Sustainable Development Goal for drinking water (i.e., to achieve universal and equitable access to safe and affordable drinking water for all by 2030).
Although information about domestic well use in developing countries is difficult to obtain, Bangladesh is an exception because domestic wells there have been extensively studied due to concerns about arsenic in groundwater. It is estimated that there are about 17 million domestic wells in Bangladesh (Fischer et al., 2020; Shamsudduha et al., 2019), serving a population of approximately 107 million people. The total number of wells has been steadily growing and a larger percentage of these wells are now privately owned domestic wells. In 1992 the total number of wells in Bangladesh was 2.5 million, 50 percent of which were privately owned and 50 percent were publicly owned. In 2017, the total number of wells was estimated to be 18.4 million, 95 percent of which were privately owned (Fischer et al., 2020). About 15 percent of these domestic wells are in urban areas and the remainder are in rural areas.
It is important to know how many domestic wells are in use and where they are located to determine where people are at risk of exposure to groundwater contaminants. An understanding of the distribution of domestic wells allows targeted interventions (e.g., awareness programs, well water quality testing programs) to be carried out in areas with suspected groundwater contamination. In many cases we can predict which areas are more likely to be at risk from naturally occurring and anthropogenic contaminants. Most naturally occurring groundwater contaminants, such as arsenic and fluoride, come from geologic sources, and the association between these contaminants and specific geologic formations indicates areas are more likely to be impacted. Anthropogenic groundwater contaminants can also be associated with specific areas where human activities pose risks to groundwater, such as agricultural areas where groundwater is often impacted by microbial contaminants, nitrate, and pesticides.
It is also important to know where domestic wells are being used so that water withdrawals from these wells can be included in water budgets. This can be especially important in highly stressed aquifers where the total water withdrawals have reached the aquifer’s sustainable limit, or in areas where there is a risk that over-pumping may cause seawater intrusion. In most aquifers, agricultural, municipal, and industrial water withdrawals account for most of the groundwater withdrawal. However, depending on local conditions, a significant proportion of groundwater withdrawals can come from domestic wells.
Groundwater budget calculations for the Province of Nova Scotia, Canada, indicate that 32 percent of the groundwater withdrawals in the province are from domestic wells (Figure 2). The relative proportion of groundwater withdrawals for domestic wells in the province is larger than for most aquifers. Usually, domestic well withdrawals represent a small proportion of the total pumping volume. In addition, where domestic septic systems are in use, most of the water pumped from domestic wells is returned to the shallow aquifer though septic system discharge.