Introduction
Household self-supply of drinking water, encompassing privately owned and managed sources like wells and rainwater harvesting systems, is increasingly recognized as a significant factor in LMICs. While extensively studied in sub-Saharan Africa, its role in the Asia-Pacific region remains relatively unexplored, despite evidence suggesting its widespread prevalence. This study aims to address this gap by quantifying the extent of self-supply in the Asia-Pacific, characterizing the types of sources used, and analyzing temporal trends. The significance of understanding self-supply stems from its implications for water policy (often overlooked due to its private nature), sector financing (household investment representing a major, often unacknowledged, financial contribution), and public health (water quality concerns arising from the lack of routine monitoring of these private sources). A clearer understanding of self-supply is crucial for interpreting progress toward SDG target 6.1 (safely managed water services), particularly as self-supply generally meets the criterion of on-premises availability, but its compliance with other criteria (freedom from contamination and sufficient quantity) remains unclear. This also impacts the understanding of how self-supply aligns with the human right to water.
Literature Review
The existing literature highlights the significance of self-supply in providing household water in LMICs, with a particular focus on sub-Saharan Africa. Studies in this region have explored various aspects of self-supply, including its cost-effectiveness, its role in reaching hard-to-reach rural populations, and challenges in governing and monitoring groundwater use. However, research on self-supply in the Asia-Pacific region has been limited despite evidence suggesting its prevalence in several countries. This gap in knowledge necessitates the present study to provide a regional assessment of self-supply practices, considering its implications for water policy, financing, and public health.
Methodology
This study utilized 77 national datasets from 26 LMICs across South Asia, Southeast Asia, and the Pacific. Datasets included national surveys and censuses, sourced from various online repositories, including the Joint Monitoring Programme (JMP), Demographic and Health Surveys (DHS), Multiple Indicator Cluster Surveys (MICS), and The Pacific Community (SPC) Statistics for Development Division. Self-supply was defined as groundwater or rainwater sources located on-premises or explicitly designated as household-owned. Data analysis was performed using SPSS (v26) with sample weights, categorizing self-supply sources based on JMP classifications (borehole/tubewell, protected well, unprotected well, rainwater collection). Prevalence was calculated at country and regional levels based on the proportion of the population relying on self-supply as a primary drinking water source. Two methods were used to estimate prevalence: Method 1 used the most recent dataset for each country, applying this proportion to 2018 population figures. Method 2 employed best-fit regression lines for countries with multiple datasets to estimate 2018 prevalence. Temporal trends were assessed for countries with multiple datasets since 2000, examining changes in both absolute numbers and proportions of the population using self-supply. Additional analyses explored seasonal variations, non-drinking water uses, and source type distribution where data allowed. Challenges included inconsistencies in data reporting regarding on/off-premises distinctions and private/communal ownership. Where possible, ratios were estimated using data from earlier datasets or neighboring countries.
Key Findings
The analysis revealed that approximately 32% of the population in the study region relied on self-supplied drinking water in 2018, equating to roughly 780 million people. This reliance was highest in South Asia (33%), followed by Southeast Asia (29%), and was lower in the Pacific (15%). The prevalence varied significantly across countries, ranging from ubiquitous usage in Bangladesh (71%) and the Marshall Islands (79%) to minimal use in Bhutan (0%) and Fiji (4%). India, Bangladesh, Pakistan, and Indonesia collectively accounted for 85% of self-supply users. Self-supply was more common in rural areas (38%) than urban areas (21%), although this pattern reversed in the Pacific. When including non-drinking water uses by households primarily using bottled water, the prevalence of self-supply increased to 45% in Southeast Asia (an additional 70 million people). Groundwater sources (boreholes/tubewells) predominated in South and Southeast Asia, while rainwater collection was the dominant form of self-supply in the Pacific. Analysis of temporal trends across 20 countries indicated a yearly increase of 9.4 million self-supply users, with stability in the proportion of the population using self-supply (31% after adjusting for temporal trends). This stability resulted from divergent trends; increases in rural areas and decreases in urban areas. Some countries exhibited yearly increases of over 0.5% points (e.g., Bangladesh, Cambodia, Nepal, Vanuatu), while others saw declines of over 1% (e.g., Thailand, Tonga, Vietnam, Indonesia).
Discussion
The findings underscore the substantial role of self-supply in the Asia-Pacific, with approximately one in three households relying on this method. The ongoing growth of self-supply emphasizes its continued importance in securing household water. The estimates likely underestimate the true dependence due to limitations in data collection on non-drinking uses (beyond households using bottled water for drinking) and the potential sharing of water sources among households. This highlights the need for improved data collection methods. Governments face the challenge of balancing the opportunities and risks associated with self-supply. While self-supply offers advantages, such as an additional source of funding and household-level management, it also presents difficulties in monitoring and regulating water quality and may hinder the economies of scale achievable through centralized systems. The study highlights significant funding for water supply improvements originating from households, mostly unaccounted for in sector planning. Only Bangladesh provided an estimate of household investment. Data limitations also hinder the assessment of whether self-supplied water meets all 'safely managed' criteria for SDG 6.1. Water quality remains a key concern, and existing data predominantly focus on utility-operated services, leaving a large segment of the population unaccounted for. The resilience of self-supply to climate change also warrants further investigation, as individual households may face more challenges adapting to changing conditions than larger service providers.
Conclusion
Self-supply of drinking water is widespread in the Asia-Pacific, representing a substantial and often overlooked aspect of water service delivery. This study provides crucial quantitative evidence on its prevalence, types, and trends. The findings highlight the need for policies that balance the opportunities and risks of self-supply, considering its financial contribution, water quality implications, and resilience to climate change. Further research is needed to understand the equity implications, drivers of household investment, and effectiveness of potential policy interventions. Improved data collection, incorporating water quality testing and information on secondary water sources and water sharing, is crucial for a more comprehensive understanding of self-supply's role in water security.
Limitations
The study's estimates are subject to limitations in data availability. The prevalence of self-supply is likely underestimated due to limited data on secondary water sources, water sharing among neighbors, and inconsistencies in data reporting on on/off-premises and private/communal distinctions for groundwater and rainwater sources. These data limitations hinder a full assessment of whether self-supplied water meets the 'safely managed' criteria of SDG 6.1, particularly concerning water quality and sufficient quantity. Temporal trends could only be analyzed for a subset of the included countries.
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