Urban Water Resilience Infrastructure Falling into Oblivion: The Case of Warsaw’s Oligocene Groundwater Intakes

Abstract

Warsaw’s Oligocene Groundwater Intakes (OGIs) represent a unique but overlooked component of the city’s Urban Water System (UWS), originally developed to supplement municipal supply. This study investigates whether the existing OGI network can still contribute to Urban Water Resilience (UWR) under contemporary conditions. A mixed-methods approach was applied, combining archival research, geospatial analysis of 89 public intakes, and on-site assessments of selected facilities in the Praga Północ and Praga Południe districts. The results show that while OGIs form a decentralized and technically functional system with high resilience potential, their spatial coverage is uneven, their public use has sharply declined, and management is fragmented across multiple entities. Despite this marginalization, OGIs retain strategic value as an emergency safeguard and could be revitalized as part of Warsaw’s resilience strategy.

1. Introduction

The resilience concept, originating from ecological systems research, is defined as the capacity of a system to endure by preserving its core structure and functionality—its integrity—when exposed to shocks or disruptions [1]. The primary aim of engineering system resilience is to maintain continuous and efficient system performance during or following a failure event [2,3]. In urban systems, resilience is the ability to respond to disruptions in those systems. Consequently, Urban Water Resilience (UWR) is defined as the capacity of Urban Water Systems (UWS) to absorb disturbances, adapt to changing conditions, and recover functionality after climate extremes, infrastructure failures, and socio-economic stresses [4]. Several studies describe it as a multi-level construct that blends technical performance with human, governance, and environmental dimensions [4,5,6,7,8,9].

One of the key elements of UWR to address unforeseen threats is incorporating redundancy and flexibility into their design, upgrades, or rehabilitation efforts [8]. Residential areas often rely on wells, boreholes, and bottled water without a municipal water system. In such a case, groundwater reserves should be considered a carefully managed strategic resource that supplies local communities with water [10]. In emergencies, this resource can serve as a backup system. Planning the redundancy of the UWS can be enhanced by introducing a centralized storage tank. At the same time, flexibility can be achieved by increasing network connectivity and using distributed storage tanks [8]. Groundwater plays a vital role in promoting urban sustainability and is essential for developing climate-resilient strategies in cities [11].

Warsaw was among the first European cities in the nineteenth century to equip its residents with a modern water supply network [12]. Conceived under Russian imperial rule and engineered by William Lindley, the system was intended to eliminate the city’s open sewers and spur urban growth through improved public hygiene. Today, that legacy endures in a three-unit arrangement called the Central Network Scheme [13]. The Central Waterworks (Wodociąg Centralny) extracts surface, bay, and sub-bottom water from the Vistula River and partially from the Praga Waterworks, delivering treated water to the historic left-bank core and selected western districts. The Praga Waterworks (Wodociąg Praski) relies on infiltration intakes—including the iconic mid-river shaft “Gruba Kaśka”—and supplies the right-bank districts and the lower left-bank city. A third unit, the Northern Waterworks (Wodociąg Północny), abstracts surface water from the Zegrze Reservoir to serve northern suburbs. This tripartite structure, coupled with dual sourcing from the Vistula and Narew catchments and a ring-shaped transmission network, affords Warsaw a high degree of operational redundancy and crisis robustness.

Beneath the city lies an additional, largely invisible component of Warsaw’s water landscape—groundwaters: the Quaternary aquifer and the Oligocene aquifer. Quaternary aquifers consist mainly of sandy and gravelly sediments deposited during the Pleistocene and Holocene, forming a key shallow groundwater source for the region. Below the series of Pliocene clays and Miocene silty sands, silts, and clays, the Oligocene aquifer is located at a depth exceeding 200 m. This confined aquifer formed during the Oligocene epoch is recharged slowly through natural filtration [14]. Nowhere else in Poland are publicly accessible Oligocene Groundwater Intakes (OGIs) as numerous as in Warsaw, where hundreds of wells were sunk during the twentieth century to tap this resource. Awareness of the climate crisis and the increasing number of armed conflicts in recent years justifies the possibility of using Oligocene waters to support the city’s resilience.

Scientific publications on Oligocene water in Warsaw focus on the issues of natural and engineering challenges of groundwater management [14,15], water quality, and chemical composition [16], or trends of groundwater level change of the Oligocene aquifer [17,18]. To the authors’ knowledge, no scientific publications have analyzed the development and spatial coverage of the network within the structure of a dynamically developing city like Warsaw. Furthermore, the authors found no publications evaluating the current technical condition of Oligocene Groundwater Intakes or their management. These are key aspects that allow for assessing the feasibility of utilizing the OGI network to support Urban Water Resilience. Therefore, this study aims to answer the following research questions: Does the OGI network provide access for all Warsaw residents? Is there still a need for their use, and are OGIs being utilized? Who manages them, and what is their technical condition?

2. Methods

This study adopted a mixed-methods approach that combined (1) historical and documentary analysis, (2) geospatial inventory and mapping, and (3) on-site qualitative fieldwork anchored in a comparative case study framework. Triangulating these techniques made it possible to trace the long-term evolution of the Oligocene groundwater network, assess its present spatial coverage, and examine the technical condition and functioning of selected OGIs in situ.

To reconstruct the development of the network of Oligocene Groundwater Intakes in Warsaw, we conducted a historical and documentary analysis reviewing: archival documents held by the Polish Geological Institute, municipal and hydrogeological reports, peer-reviewed publications on underground water in Warsaw, local press, grey literature, and online repositories. Content analysis focused on the history of intake network development, policy interventions, and ownership patterns.

• To analyze the spatial coverage of the OGI’s network in Warsaw and verify its accessibility, a citywide geodatabase of 89 extant public intakes was compiled by merging official registers from the municipality’s environmental department, intakes’ locations geotagged on Google Maps, digital layers released by Warsaw’s Geoportal (2022 edition), and field verification. Each OGI was geocoded and overlaid with data presenting urban morphology. For the selected Warsaw districts—Praga Północ and Praga Południe—service-area analysis with an 800 m walking buffer (≈10 min) was conducted to identify coverage gaps. Spatial outputs were exported as high-resolution images for figure preparation.

Eleven intakes in the Praga Północ and Praga Południe districts were selected for a detailed field study and a comparative case study to investigate OGI’s technical conditions, functioning, and management patterns. Between April and July 2022, each site was inspected, and using a standardized checklist, quantitative data were captured. The data was collected to allow the comparison of the characteristics of OGIs in three analytical dimensions:

• Location characteristics (public park, public square, street, and hospital premises) and accessibility (tap location outside/inside building, and fencing the area);
• Architecture (type of the facility: building/shed) and technical condition (good—minor signs of wear, moderate—significant signs of wear, and poor—condition requiring a major renovation);
• Management (type of managing entity: housing cooperatives, municipality departments, and hospitals);
• Geotagged photographs and rapid sketches of internal layouts complemented field notes. Quantitative data (inventory attributes) and qualitative material (field notes) were compiled in Microsoft Excel and subjected to comparison.

Data triangulation (archival, spatial, and observational) mitigated source bias. Through the integration of historical documentation, spatial analysis, and systematic fieldwork, the methods outlined above provide a robust basis for the results presented in the subsequent sections of this article.

3. Results

3.1. Past and Present Use of Oligocene Groundwater Intakes

The first well tapping into Oligocene water in Warsaw was drilled in 1897 on the premises of the State Monopoly Warehouses in the Praga district to serve a distillery. At the time, the artesian pressure was so intense that water surged up to 14.5 m above ground level [19]. In the early 20th century, artesian wells began to be drilled primarily to meet the needs of the emerging industrial facilities in Warsaw [20]. Until the 1960s, most OGIs were privately owned and mainly served industrial facilities, hospitals, service centers, or military units. At that time, the quality of Oligocene water made it attractive for industrial use, as it eliminated the need for costly purification processes. Permission was readily granted to build a new OGI, as the reduction in their pressure did not cause any problems in operation and was not considered to be the result of excessive water intake. As a result, in the 1970s, Oligocene water was used in 103 plants and institutions in Warsaw, of which only 36 used it for drinking purposes and for the production of food products [15]. Intense exploitation at that time led to a significant drop in the water table—up to 50 m lower than previous levels—prompting city authorities to ban the construction of new industrial intakes and restrict overall withdrawals [14]. After introducing a ban on industrial use and restrictions on water consumption, the pressure was restored within a few years, proving that this resource was being replenished and effectively drained. Gradually, filtration systems were added at several sites over this period, and access to water intakes was extended to the public.

The 1990s saw a peak in the popularity of OGI, resulting in over 100 new intakes established across Warsaw. The chlorinated and discolored tap water supplied by the municipal system contributed to the popularity of Oligocene water, which was perceived as a purer, safer alternative. Back then, bottled mineral water was beginning to appear on store shelves. A 1996 geological review evaluating this resource’s chemical composition and potability included samples from 170 collection points in Warsaw and surrounding areas [16].

At the height of its popularity, Oligocene water was not just a trend—it became a staple in many households. Proximity to an intake became a real estate advantage. Newly built housing developments sought their own intakes to align with the trend and respond to the poor quality of piped water. The intakes served a local function but remained open to the broader public. Oligocene water was clean, tasty, free of charge, and readily available. Daily trips to collect water in plastic containers became an urban ritual. People fetched the water on foot or by car. Urban legends flourished about the water’s supposed healing properties, owing to its name suggesting an age of over 25 million years.

Today, the relevance of Oligocene water has diminished. Warsaw’s Municipal Waterworks and Sewage Company (MPWiK) has, over the years, invested heavily in advanced water treatment technologies, particularly in purifying Vistula River water. The quality of tap water in the city is significantly higher than it was in the 1990s. This contributed to the gradual disappearance of the phenomenon of daily trips to collect water [21].

Over the past decades, reduced use of Oligocene water has contributed to restoring hydrostatic pressure, resulting in a rise in potentiometric levels [17]. In contrast, the Quaternary aquifer has exhibited an opposite trend, with a declining water table. Additionally, long-term changes in the properties of Quaternary aquifer springs have been observed, including a gradual decrease in discharge, an increase in water temperature, and shifts in hydrochemical composition—reflecting the combined impacts of climate change and human activity [22]. Recent studies have also highlighted a high risk of secondary contamination within the domestic distribution system of the Warsaw UWS [23].

In this context, the extensive reservoir of clean, potable Oligocene water—accessible through simple, localized treatment methods—holds renewed potential. From the perspective of urban resilience, these intakes could be strategically reconsidered as emergency water sources or as elements of decentralized infrastructure supporting climate adaptation and crisis preparedness.

3.2. Spatial Structure and City Coverage of the Network of Oligocene Groundwater Intakes

Eighty-nine public Oligocene water intakes have been identified in Warsaw (Figure 1). They are in highly urbanized areas, near hospitals, public parks, or housing estates built in the 20th century. Most of them are in the western part of Warsaw. The largest concentrations are observed in the Bemowo district (12), Śródmieście (10), and Bielany (9). The city’s eastern part has large areas without access to such infrastructure. In particular, the Wawer and Miłosna districts do not have a single Oligocene water intake, while Praga Północ and Praga Południe have four and seven intakes, respectively.

A detailed analysis of the distribution of Oligocene water intakes in the Praga Północ and Praga Południe districts aligns with citywide patterns. The intakes are located on hospital grounds as backup water sources and within housing estates developed in the 20th century. The map (Figure 2), which shows circles with an 800 m radius around each intake, illustrates that the intakes are regularly distributed across these districts, generally ensuring pedestrian access for residents.

However, particular areas within both districts lack adequate pedestrian access to such infrastructure. These include some 20th century housing estates and areas currently undergoing significant urban transformation. This is especially true for dense residential developments from the 21st century built on former industrial sites, such as the northern part of Kamionek in Praga Południe and Pelcowizna in Praga Północ.

3.3. Case Study of Oligocene Groundwater Intakes

The Oligocene water intakes in Warsaw’s Praga Południe and Praga Północ districts represent a diverse and dispersed network of small-scale public infrastructure (Figure 3). Primary data collected during the on-site visits are summarized in

Table 1. Comparison of the characteristics of Oligocene groundwater intakes in the Praga Północ and Praga Południe districts.

No.	Street	District	Location	Management	Type	Technical Condition	Tap Location	Fenced Area
1	Plac Hallera	Praga Północ	public park	municipality department	building	good	inside/ outside	yes
2	Strzelecka	Praga Północ	street corner	municipality department	building	moderate	inside/ outside	yes
3	Łochowska	Praga Północ	public square	municipality department	building	good	inside/ outside	yes
4	Panieńska	Praga Północ	hospital premises	municipality department	building	good	inside	yes
5	Majdańska	Praga Południe	public square	housing cooperative	building	good	inside/ outside	yes
6	Motorowa	Praga Południe	public square	municipality department	building	moderate	inside/ outside	no
7	Lizbońska	Praga Południe	public square	housing cooperative	building	moderate	inside	no
8	Szaserów	Praga Południe	public square	housing cooperative	shed	moderate	outside	no
9	Walecznych	Praga Południe	public square	municipality department	building	good	inside/ outside	yes
10	Garwolińska	Praga Południe	along street	hospital	shed	poor	outside	no
11	Grenadierów	Praga Południe	hospital premises	hospital	building	moderate	inside/ outside	no

and described below.

3.3.1. Location Characteristics and Accessibility

Most intakes are located near secondary or service roads that play an essential role in neighborhood circulation. Visibility within the cityscape is variable. Some intakes are prominently placed in public parks or squares (e.g., Plac Hallera), while others are hidden within hospital premises or residential enclosures. All structures are within a few hundred meters of public transport access—typically 100–450 m—and are generally reachable on foot. However, rare bicycle racks and dedicated car parking limit multimodal accessibility.

In most cases, access to the water intake may be limited. They are located on fenced plots with a locked gate or in buildings that can also be locked. This allows administrators to control their access and limit misuse at night, when they are closed. Only those not located within a fenced area and equipped with external taps offer 24/7 access.

3.3.2. Architecture and Technical Condition

The architectural expression of the intakes varies significantly. Generally, all inspected intakes are placed inside a building or a shed. Such buildings feature traditional gabled roofs, evoking domestic or pavilion-like structures and often following symmetrical layouts. A few, such as those at Plac Hallera and Majdańska, exhibit strong formal similarities, while others, like the rotunda at Motorowa or at Grenadierów, present distinctive interpretations ranging from postmodern to utilitarian. The intake at Panieńska is notably austere—a simple building tucked behind hospital walls—while the structure on Garwolińska resembles a neglected bus stop. The interior layout of OGIs located in buildings is typically straightforward, with taps aligned along the geometry of the space, and the entrance opposite the faucets’ primary wall. Better designs include windows at eye level or side-facing taps, reducing the discomfort of standing with one’s back to the entrance. Others, however, feel dark, enclosed, and potentially unsafe.

Most of the OGIs are in good or moderate condition. The buildings in moderate condition show significant signs of wear, and the walls near the intakes are covered with limescale. The interior was often damp, and the floor had puddles of water and dust. The building on Garwolińska Street is in the worst condition, appearing poorly managed and requiring a significant renovation.

3.3.3. Management

OGIs are individually managed by a mix of entities—housing cooperatives, municipality departments, and hospitals. In Praga Północ, all OGIs are managed by the same municipality department responsible for managing all district properties. In Praga Południe, however, they are managed by various entities, respectively, housing cooperatives (3), the municipality department (2), and hospitals (2). Scattered governance contributes to inconsistent maintenance and aesthetic quality, and lacks centralized information, signage, or branding.

4. Discussion

This study evaluated the present-day condition and strategic value of Warsaw’s Oligocene Groundwater Intakes (OGI) and interrogated how it can contribute to contemporary urban-resilience agendas.

The collected data indicate the existence of an extensive, decentralized network that scores highly on independence (deep confined aquifer), flexibility (each intake is independent from all the others), and dispersal (dozens of nodes distributed across the city). This system is redundant with the Warsaw Urban Water System. According to Mugume et al. [8], such features increase the resilience of the Urban Water System. As such, the OGI network can strengthen Urban Water Resilience, which is consistent with the findings of Grönwall et al. [10].

At the same time, our study shows that OGIs in Warsaw are falling into disuse and oblivion, questioning their relevance in supporting urban resilience. The following discussion examines the fundamental limitations of this network, which are related to uneven spatial coverage of the city, the lack of current need for its use, and the lack of coordinated management, and considers possible future scenarios.

Uneven spatial coverage of the city. Warsaw’s 89 public OGIs form a loose mesh at a metropolitan scale that roughly parallels twentieth century urbanization corridors. Analysis shows concentrations in western districts (Bemowo, Bielany, and Śródmieście) and marked deficits in eastern peripheries such as Wawer and Miłosna. Mapping the 800 m service area within Praga districts shows that historic housing estates and hospital compounds are within walking distance, whereas high-density, post-industrial redevelopments in Kamionek and Pelcowizna are not. These findings highlight a tension between legacy distribution and contemporary need: newer residents in rapidly intensifying neighborhoods are least likely to benefit from the fallback resource, even though population density—and potential demand during a crisis—is rising fastest there. Addressing this mismatch will require either selective infill drilling of new intakes or the strategic retrofitting of existing but dormant wells.

No current need for use. The intensive development of the OGI network in Warsaw in the 1990s was driven by the poor quality of the city’s tap water, which made these intakes a valuable resource for households and led to widespread use. Since then, investments in advanced purification technologies have significantly improved the safety and taste of the city’s tap water, eliminating the need for daily Oligocene water collection. As a result, OGIs are now rarely used by a decreasing number of regular users. The technical conditions of the intakes may contribute to users’ reluctance to use them. The need to utilize OGIs would undoubtedly arise in a crisis affecting the Urban Water System, limiting or preventing tap water use.

Lack of coordinated management. OGIs are managed by a patchwork of institutions: housing cooperatives, municipality departments, and hospital administrations; no city-level office coordinates management of all OGIs. The absence of a coordinating agency manifests in uneven opening hours, ad hoc repairs, and, crucially, a lack of real-time communication with the public. Users are not informed what Oligocene water is and how it differs from tap water; moreover, they cannot easily learn which intakes are operational, how to find them, or how the water compares with municipal standards. The lack of coordination in OGI management may result in a lack of daily use, but this will be particularly critical in the event of a crisis. The lack of aggregated information on the technical condition of intakes and monitoring their use will significantly impede decision-makers in managing the crisis. Furthermore, the lack of visual identification of intakes and the lack of social awareness among residents can cause chaos and stress in situations where a real need for OGI utilization arises.

Possible future scenarios. Fragmented stewardship leaves many pavilions aesthetically neglected and operationally uncertain. Various governing bodies have different motivations for maintaining the usability of OGIs. For some, such as housing cooperatives, owning OGIs is no longer an advantage but an unnecessary expense. This can eventually lead to their deterioration, leading to closure. At the same time, as studies have shown, a large portion of OGIs are managed by municipality departments, which ensure their maintenance. In such a situation, taking over the OGI’s management from housing cooperatives by municipal entities may be the best strategy for their survival. Therefore, three possible future scenarios emerge. Scenario A: Managed decline—allow most intakes to fade, preserving only a handful on hospital grounds for contingency use. This is the least costly in the short term, but it forfeits redundancy and wastes the potential of already developed infrastructure. Scenario B: Passive safeguard—keep pavilions locked and serviced, ready to be opened in emergencies. While it increases reliability and security, it limits access to the infrastructure for existing users, prevents daily use, and risks public unfamiliarity with operation protocols when disaster strikes. Scenario C: Active revitalization—rebrand intakes as public amenities, retrofit the worst pavilions, drill modestly in underserved districts, and embed OGI data in the city’s open-data dashboard. This strategy requires the most significant investment in the expansion, modernization, and maintenance of OGIs. Still, it preserves the existing infrastructure, maintains universal and free access to Oligocene water, and sustains the existing use of these sources.

Warsaw’s competitive advantage lies in already having a ready-made, if ageing, network of OGIs. The capital expenditure required to renew OGIs is modest relative to the cost of drilling new boreholes. Of the three, Scenario C most closely aligns with international resilience frameworks championing hardware redundancy and social adaptability.

Limitations and avenues for further research. This study is geographically limited to two districts of Warsaw and temporally limited to a short-term observation window. The status of the OGI network in Warsaw is constantly changing, with new intakes being closed each year. Therefore, similar studies should be regularly updated and conducted in other districts of Warsaw. Further research would be worthwhile in conducting quantitative studies of the number of people using individual intakes at different times of the year. Furthermore, detailed analyses of the number of Warsaw residents who could use OGIs during a potential crisis with intake capacity and water resources in the Oligocene aquifer should be conducted. The possibility of expanding the OGI network in Warsaw should be thoroughly analyzed, particularly in dynamically developing areas where intakes are not present. The legal framework for creating new OGIs should also be examined, particularly regarding the possibility of supplementing the basic functional program of intakes with educational and informational functions within the OGI and its surroundings. It is advisable to conduct comparative studies in other Polish cities with public groundwater intakes, which clarifies whether the Warsaw patterns are generalizable or whether the dynamics of the capital create specific management challenges.

5. Conclusions

This study examined the historical development, spatial distribution, technical condition, and management of Warsaw’s Oligocene Groundwater Intakes (OGIs) to assess their present role and potential contribution to Urban Water Resilience. The findings highlight a paradox: while the OGI network constitutes a unique and strategically valuable element of Warsaw’s urban infrastructure, it is simultaneously drifting into neglect and marginalization.

First, the historical analysis revealed how OGIs evolved from industrial and institutional installations into public resources, reaching their peak popularity in the 1990s when municipal tap water was of lower quality. However, their use has sharply declined due to significant improvements in tap water quality, leading to reduced public demand and diminished awareness of their relevance.

Second, the geospatial analysis confirmed that the city retains an extensive network of 89 public intakes, with substantial concentrations in historic districts but significant gaps in rapidly growing post-industrial areas. This uneven distribution limits equitable access and diminishes their effectiveness as a citywide resilience resource.

Third, fieldwork demonstrated that most OGIs remain structurally sound, though some require urgent renovation. Significantly, the management of OGIs is fragmented across different entities, resulting in inconsistent maintenance, limited information for residents, and a lack of strategic coordination.

Taken together, these findings suggest that OGIs, despite their underutilization, retain substantial potential as a decentralized and independent safeguard for Warsaw’s Urban Water System. They embody redundancy, dispersal, and flexibility principles central to Urban Water Resilience. However, realizing this potential depends on deliberate policy choices. City decision-makers must decide whether to let OGIs gradually decline, preserve them as dormant emergency assets, or actively revitalize them as accessible and recognizable public amenities.

The latter scenario offers the most significant long-term benefits from a resilience perspective. Revitalizing and selectively expanding the OGI network could strengthen Warsaw’s preparedness for climate extremes, infrastructure failures, or other crises while fostering public awareness of water as a strategic resource.

In conclusion, the OGI network should not be regarded as an obsolete relic, but as a latent asset capable of bolstering the city’s adaptive capacity. Recognizing, maintaining, and integrating OGIs into Warsaw’s resilience planning would not only safeguard a unique hydrogeological resource but also enhance the city’s ability to respond effectively to an uncertain future.