Discussion
We present the development and validation of the first scale that quantifies experiences of household water insecurity in an equivalent way across low-income and middle-income countries. The scale uses simply worded questions to probe about household water access, availability and use, and can be administered in approximately 4 min. The ability of the HWISE Scale to comparably measure key universal household water insecurity experiences across diverse geographic, cultural and water-provisioning contexts satisfies an urgent need articulated by policymakers, governments and scholars.7 29
By quantifying experiences across multiple components of household water insecurity (accessibility, adequacy, reliability and safety), the HWISE Scale represents a fundamental advance in our ability to measure this phenomenon. For other global health issues, the advent of high-resolution, experiential measures has informed basic science, public health and international policy. For instance, food insecurity was only solely assessed using food availability via national-level and regional-level food balance sheets, which are analogous to current measures of water availability.9 In the last 25 years, the inclusion of food access, use and acceptability in experienced-based scales (eg, Food Insecurity Experience Scale,30 Household Food Insecurity Access Scale21) has provided a comparable measure for monitoring and evaluating food insecurity worldwide.20
This more comprehensive measurement of food insecurity has been transformative. Specifically, the advent of high-resolution measures of food insecurity has increased the number and rigour of studies of food insecurity; revealed its deleterious consequences for physical and mental health31 and cognitive development32 33; and informed the development of programmes and policies that address food insecurity.34 35 The creation of household-level measures of food insecurity made it unmistakable that food insecurity is highly prevalent and threatens health and economic productivity, and ultimately served as a tool to help mitigate food insecurity.
The use of the HWISE Scale could be similarly transformative for our understanding of water insecurity. Specifically, the scale permits comparative studies that quantify the multiple components of water insecurity with higher resolution than currently possible, allowing for the identification of global inequities, as well as vulnerable sub-populations within communities. The scale also has the potential to identify determinants of water insecurity and assess the health, economic and psychosocial consequences of household water insecurity, including food insecurity.36 Furthermore, the scale could be used to monitor trends in water insecurity over time, such as how it is shaped by macro-level social, economic and political shifts; climatic variability; and local shocks, such as extreme weather events or contamination. These scale data can, in turn, be used to select water-related programmes, technologies and policies to implement, and to evaluate their impacts and cost-effectiveness. The scale’s ease-of-use makes it appropriate for adoption in both community-led self-evaluation efforts and for large-scale monitoring and evaluation.
The HWISE Scale can also complement existing indicators to more comprehensively measure progress towards the SDGs. Current JMP survey items provide critical data on the quality and accessibility of drinking water sources,11 but they do not quantify other necessary components of water insecurity, including reliability, acceptability or adequacy across multiple uses. As such, the prevalence of problems associated with securing and benefiting from safe water could be significantly underestimated.12 13
For instance, a household classified as having a safely managed drinking water source using the current JMP service ladder may not be able to reliably access this source (eg, due to intermittent supply, water rationing, non-functional water technologies, unaffordability). This unreliable access, in turn, can drive households to seek water from a lower-quality secondary source, cause changes in critical water-related activities (eg, food preparation, handwashing) and alter daily routines.37–41 All of these components of water insecurity would go uncaptured if only the JMP survey items were applied.
Indeed, the proportion of water-insecure households, as identified using the HWISE Scale, is different from and more comprehensive than the proportion using a sub-optimal drinking water source, according to JMP standards (online supplementary figure 4). As such, the unique ability of the HWISE Scale to concurrently measure multiple components of household water insecurity has the potential to provide a more robust assessment of SDG 6, ‘ensure access to water and sanitation for all’.
The HWISE Scale is also consistent with the SDG principles of ‘universality’ and ‘leaving no one behind’, in that the scale can be easily implemented in low-income and middle-income countries, and the data it generates can be disaggregated to identify vulnerable populations. Further, it satisfies a call for a more holistic conceptualisation of water and sanitation.42 Just as the prevalence of household food security is an indicator for SDG 2 (‘no hunger’), household water insecurity could be a key target for improved health and well-being that can be tracked using the HWISE Scale.
The HWISE Scale captures components of water insecurity that are experienced universally across low-income and middle-income countries. To do this, however, the final scale is necessarily reductionist. Supplemental items or modules tailored to local experiences and evaluation needs may be used to complement the HWISE Scale. For example, agriculture-focused endeavours may retain the items on water for crops, gardens and livestock that were dropped; others may find the items pertaining to children’s well-being important (eg, school attendance, bathing; table 2, online supplementary table 1). Further, there are other water insecurity experiences that may be salient in some settings but are not captured in this scale, for example, affordability, which could be measured with additional items.
Strengths of this study include the diversity of sites, rigour of data collection and analytic methods, and use of best practices in scale development. Limitations include that, although samples from each site were sufficiently large and most were random, they were not necessarily representative of the state or country.
Development and validation of the HWISE Scale is only one step toward understanding and mitigating water insecurity. The HWISE Scale must be widely implemented in order to generate data that help to understand and monitor the prevalence, aetiologies and consequences of household water insecurity. A further next step is to evaluate if the HWISE Scale is valid in high-income countries. The tentative cut-point of 12 as the preliminary threshold for defining water-insecure households should also be revisited when there are sufficient data to evaluate relationships with other adverse outcomes, for example, morbidity or agricultural productivity. Lastly, multiple levels of water insecurity could be considered (eg, high vs low water insecurity).
In sum, the HWISE Scale provides a universal, simple measure to comprehensively capture complex, household-level relations between people and water in low-income and middle-income countries. Given that water insecurity is a linchpin in human health disparities and the structural dynamics of poverty and economic development,2 4 6 7 11 16 the use of the HWISE Scale could be transformative in many arenas. As problems with water become more common and severe, the data that the HWISE Scale generates can guide the international community’s ambitious development agenda by contributing an evidence base for clinical, public health and policy recommendations regarding water.