Climate Change Places New Pressure on Coastal Water Supplies
Coastal communities face a double challenge as climate conditions become more variable. Longer or more intense dry periods can reduce rainfall and groundwater recharge, while rising pressure on coastal aquifers can increase the risk of seawater intrusion.
South Flores is particularly vulnerable because many households depend on seasonal rainfall and shallow groundwater, while surface-water resources are limited and fluctuate throughout the year. When freshwater reserves decline, seawater can move farther into coastal aquifers, increasing salinity and reducing the suitability of groundwater for household use.
Valentinus Tan's study treats the problem as more than an infrastructure issue. Water security depends on three interconnected factors: the amount of water available, its quality, and how communities organize and manage distribution.
This perspective is increasingly important for coastal regions facing climate uncertainty. Building additional infrastructure alone may not be enough if communities lack effective systems for distributing, maintaining and conserving available water.
How the Study Examined Water and Community Adaptation
Tan used a mixed-methods approach, combining measurements of water conditions with information about household and community adaptation.
The study covered four coastal villages in South Flores and involved 120 households. The selected villages were characterized by dependence on shallow coastal aquifers, limited surface-water sources and exposure to seawater intrusion.
The quantitative analysis used rainfall data from 2013 to 2023, groundwater-level measurements and salinity measurements from shallow wells between five and 15 meters deep. The study also recorded household water distribution during the dry season.
To understand how residents responded, Tan conducted structured household surveys and in-depth interviews with household heads, village water managers and community leaders. The analysis compared households using limited adaptation strategies with those combining multiple approaches.
The research process also incorporated informed consent, anonymity and data confidentiality for participants.
Raw Water Availability Fell by Nearly 29%
The hydrological analysis identified a substantial decline in dry-season water availability.
Average raw water availability during the dry season fell from approximately 2,000 cubic meters per month under baseline conditions to 1,422 cubic meters per month under climate-affected conditions. That represents a reduction of 578 cubic meters per month, or 28.9%.
The decline affected the continuity of household water supplies. Water that could previously be available throughout the year increasingly became intermittent during the dry months.
The study also found that the problem was particularly pronounced during years associated with moderate to strong El Niño events, when dry-season water deficits became more severe.
Seawater Intrusion Is Also Degrading Groundwater
Water quantity was only part of the problem. The quality of shallow groundwater also deteriorated during the peak dry season.
In areas located less than 500 meters from the coastline, average groundwater salinity increased from approximately 700–900 mg/L to as much as 1,430 mg/L. The study identifies salinity above 1,000 mg/L as a strong indication of seawater intrusion and declining suitability for domestic water use.
The most vulnerable wells were those less than 10 meters deep. The findings suggest that prolonged dry conditions can lower groundwater levels and reduce the freshwater pressure that normally limits the movement of seawater into coastal aquifers.
For communities dependent on shallow wells, this creates a serious problem: the same climate conditions that reduce the quantity of available water can also make some remaining sources less suitable for household use.
Combining Adaptation Strategies Reduced Water Scarcity
The study found clear differences between households relying on a single water source and those diversifying their supplies.
Among the 120 households, 60 used no unified adaptation approach or only one strategy. These households experienced an average of 20.3 days of water shortage per month during the peak dry season.
Another 60 households implemented at least two adaptation strategies. Their average water shortage was lower, at 15.3 days per month.
Several adaptation measures were already being used by residents:
- Rotating community water distribution: 65% of households.
- Household rainwater harvesting: 60%.
- Collective well use: 45%.
- Communal water reservoirs: 40%.
- Integrated adaptation using at least two strategies: 50%.
Overall, households implementing integrated adaptation experienced a 24.6% reduction in water-scarcity days compared with households using no adaptation or only a single strategy. The difference was statistically significant at p < 0.05.
Strong Local Institutions Make Adaptation More Effective
The findings also show that technology and infrastructure are only part of the solution.
Rainwater harvesting, collective wells and communal reservoirs can provide alternative water sources, but their effectiveness depends on how those resources are managed. Villages with active local leadership, clear distribution rules and stronger social trust were better able to reduce conflicts and maintain rotating distribution systems.
Conversely, weak coordination created problems. Interviews documented disputes over water collection schedules, difficulties maintaining communal reservoirs and declining compliance when water became extremely scarce.
The study also highlighted a gender dimension: an interview with a community representative in Village D indicated that women often carry an additional burden in finding water, while existing distribution arrangements do not always fully account for household needs.
What the Findings Mean for Water Policy
Valentinus Tan's findings suggest that climate adaptation in coastal water management should move beyond an infrastructure-only approach.
Water authorities and local governments can combine seasonal water monitoring, seawater-intrusion mitigation, rainwater harvesting, diversified water sources and community-based distribution systems. Strengthening village institutions is equally important because technical solutions may become ineffective without clear rules and community participation.
As Tan's study from Universitas Flores indicates, the resilience of coastal water systems depends not only on hydrological conditions but also on the capacity of communities to organize collectively. The study therefore supports a shift toward water governance that integrates scientific monitoring with local knowledge, social participation and institutional coordination.
In practical terms, the findings provide a model that could be considered by other coastal and small-island communities facing similar combinations of drought, groundwater dependence and seawater intrusion. However, the study recommends further longitudinal research and comparisons across eastern Indonesian coastal regions before the model's broader applicability can be established.
Author Profile
Valentinus Tan is a researcher affiliated with the Faculty of Engineering, Universitas Flores, Indonesia. His work in this article focuses on climate change adaptation, raw water resources, coastal water management, seawater intrusion and community-based adaptation. Tan is the corresponding author of the study.
The article does not provide Tan's academic degree, so no degree is added here to avoid introducing information that is not supported by the source.
Source
Article title: Community Adaptation Models to Changes in Raw Water Distribution Patterns due to Climate Change in Coastal Areas of South Flores
Author: Valentinus Tan
Affiliation: Faculty of Engineering, Universitas Flores, Indonesia
Journal: Indonesian Journal of Interdisciplinary Research in Science and Technology (MARCOPOLO)
Publication: Volume 4, No. 2, 2026, pp. 105–118
DOI: 10.55927/marcopolo.v4i2.12
URL: https://journalmarcopolo.my.id/index.php/marcopolo
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