Integrating Resilient Water Infrastructure and Environmental Impact Assessment in Borderland River Basins

Abstract

Climate-induced hydrological risks and deteriorating infrastructure present major challenges for small river basins in border regions, particularly in non-EU countries with limited institutional capacity and funding. These issues are especially acute in post-socialist contexts, where outdated hydrotechnical systems no longer meet current environmental and safety standards. This study investigates the vulnerabilities of the Uzh River basin in Uzhhorod, Ukraine—a non-EU border city with strong ecological and institutional ties to neighboring EU regions—and proposes an adaptive river management model tailored to such environments. An integrated assessment of flood protection systems, sediment transport, drainage performance, and governance gaps was conducted to inform the proposed framework, which combines structural and ecosystem-based interventions with a focus on transboundary water governance. Unlike many existing approaches that lack mechanisms for localized implementation and cross-border coordination, this model offers a transferable, evidence-based methodology for enhancing flood resilience and hydrological sustainability in similar urban areas. The insights are relevant to border cities across Eastern Europe, the Western Balkans, and the South Caucasus, contributing to both engineering practice and regional policy by aligning hydrotechnical solutions with cooperative climate adaptation strategies.

1. Introduction

Climate change is escalating hydrological extremes worldwide, placing aging water infrastructure under increasing stress. Globally and in Europe, the frequency and severity of floods have risen markedly in recent decades. For example, over 400 major flood events occurred across Europe in the last 20 years, affecting about 8.7 million people, causing more than 2000 fatalities, and inflicting over EUR 72 billion in damages [1]. At the same time, many regions are experiencing intensified droughts and water scarcity, creating a dual challenge for water management. These risks are especially pronounced in Eastern Europe’s post-socialist cities that lie outside the European Union (EU) and along national borders. Such cities often inherited Soviet-era hydrotechnical infrastructure that is now outdated and under-maintained after decades of funding shortfalls [2]. This infrastructural deficit, combined with more frequent floods and low-flow periods, leaves communities highly vulnerable to climate-related water hazards. There is a growing recognition that modernizing water infrastructure and management in these regions is urgent, and countries like Ukraine and Moldova have recently begun aligning with EU flood risk directives to improve protection measures [3]. However, adapting global best practices to local, transboundary contexts remains a significant challenge.

Uzhhorod, a medium-sized city in western Ukraine, exemplifies these issues. It is a post-socialist border city (adjacent to Slovakia) confronting both increased flood risk and periods of extremely low river flow. The Uzh River, Uzhhorod’s main watercourse, flows ~10.5 km through the city from east to west with a channel width of 30–60 m. Its banks are only partially reinforced by old stone masonry embankments dating back to the mid-20th. The current flood defense system is limited—a patchwork of levees and bank protections along urban promenades—and much of it has deteriorated. In recent years, Uzhhorod has suffered the paradox of both flood events and water shortages in the river. During spring snowmelt or heavy rains, the Uzh can overflow, yet in summer, the river often runs shallow, impairing water quality and aquatic habitats [4]. Low water levels have led to ecological problems such as stagnation, invasive vegetation growth, and fish habitat degradation. An official environmental impact assessment (EIA) of the Uzh basin confirms that the city’s hydrotechnical infrastructure is in need of modernization to address these challenges. The EIA’s findings highlight that Uzh’s flow regime is highly variable and that existing protective structures are insufficient and partially damaged. For instance, the main urban embankments (Nezalezhnosti and Students’ka waterfronts) provide some flood protection and double as pedestrian promenades, but sections require structural reinforcement and raising to meet current safety standards. Ecologically, the Uzh River in Uzhhorod remains an important habitat and migration corridor for fish, so any infrastructure upgrades must ensure minimal disruption to river connectivity and water quality.

In response, a comprehensive modernization project has been initiated under the cross-border FloodUZH program. This project—conducted in partnership between Ukrainian and Slovak water management authorities—aims to upgrade Uzhhorod’s hydrotechnical infrastructure to simultaneously reduce flood hazards and improve low-flow conditions. The core engineering intervention is the construction of a new regulating weir (low-head dam) on the Uzh River, upstream of the city center (near Bozdos’kyi Park). According to the EIA, the proposed structure is a two-section segment gate weir with an adjustable flap designed to impound water during drought periods while allowing high discharges [5]. Crucially, the design integrates a fish passage facility to maintain longitudinal connectivity for aquatic fauna and a bottom sluice (bed regulator) to periodically flush sediment and prevent. These features were included to meet strict environmental constraints—namely preserving the river’s biodiversity and water quality—as stipulated by ecological experts. The EIA conclusion emphasizes that maintaining a stable water level in dry seasons will support the river’s biota and urban landscape, but only if fish migration routes are upheld and the thermal and oxygen regimes of the water are not. In addition to the weir, the project encompasses reinforcement of the Uzh’s banks and existing flood defenses along the city reach. Approximately several kilometers of riverbank will be strengthened with modern revetments (e.g., rip-rap and renewed stone lining), tied into walking paths and maintenance roads for dual. A particularly vulnerable section of the right bank levee (along Students’ka Embankment) is slated for local reconstruction [6]. These structural measures are constrained by a requirement to avoid encroachment into the river’s natural channel where possible and to respect the 30–50 m riparian buffer that hosts valuable green spaces and protected trees. Thus, the modernization plan represents a balance between engineered flood control and environmental stewardship, informed by a robust impact assessment.

The scientific novelty of Uzhhorod’s approach lies in its integration of hydraulic engineering solutions with ecological and transboundary water management principles. Unlike conventional flood control projects of the past, which often prioritized hard infrastructure at the expense of ecosystems, the Uzhhorod plan adopts a multi-disciplinary strategy. From an engineering perspective, it introduces a hydraulic node comprising the adjustable weir, fish ladder, and sluice gate—a configuration tailored to manage both flood peaks and sustain base flows. Simultaneously, environmental considerations guided the design and decision-making process from the outset, as evidenced by dedicated biodiversity studies and fish migration analyses conducted during the EIA [7]. The result is an intervention expected to improve the river’s ecological status (by preventing complete dry-outs and creating a stable upstream pool) while still safeguarding the city from a 1% annual probability of floods. Furthermore, the project is embedded in a transboundary cooperation framework. The Uzh River crosses into Slovakia downstream, meaning any hydrological changes could impact communities and ecosystems across the border. Joint planning under the Hungary–Slovakia–Romania–Ukraine ENI CBC program has ensured that Slovak water authorities are involved in vetting the designs and that the operation of the new weir will be coordinated at the international level. This collaborative governance aspect—aligning a Ukrainian city’s water infrastructure upgrade with EU Water Framework Directive objectives and neighboring country interests—is a novel element in itself. It demonstrates a move toward integrated water resources management in a region where such an approach has lagged. Notably, the FloodUZH project also leverages modern tools like 2D hydrodynamic modeling, GIS mapping, and even mobile dam technology for temporary flood barriers [8]. This combination of gray infrastructure with “green” and innovative measures reflects a broader trend in climate adaptation planning, wherein cities employ a mix of engineered and nature-based solutions for resilience [9]. The introduction of recreation-friendly riverbanks and maintained base flow through the city is expected to yield social and environmental co-benefits, aligning the project with sustainable urban water management principles.

A brief comparison with other post-socialist cities underscores the relevance of Uzhhorod’s modernization initiative. Chișinău, the capital of Moldova, similarly faces recurrent flooding along the small river Bîc and degradation of its urban waterways. In recent years, Chișinău has developed a Green City Action Plan with support from the European Bank for Reconstruction and Development, which outlines a combination of green and grey infrastructure measures to reduce flood vulnerability [10]. This includes rehabilitating the river channel and restoring wetlands to buffer floods, alongside upgrading embankments and pumping stations. The plan was driven by data showing increasing flood frequency and damage in the city [11], much like the risk trajectory observed for Uzhhorod. In Timișoara (western Romania), the challenge of managing floods and droughts in tandem has long been recognized. There, a historical engineering solution exists in the form of the Timiș–Bega canal system, built in the 18th–19th centuries, which diverts excess water between two rivers to protect the city and provides supplemental flow during dry periods [12]. This transboundary canal (linking Romania and Serbia) remains the backbone of Timișoara’s flood defense—it safeguarded the city from extreme floods in 2005 and 2020 by channeling floodwaters away—and also serves to maintain navigation and water supply. However, maintaining such aging infrastructure is an ongoing concern; recent assessments highlight the need to modernize and adapt it to current climate conditions and safety standards [13]. Timișoara’s experience illustrates both the benefits and the sustainability challenges of long-term floodworks in a post-socialist context now within the EU. In the South Caucasus, Tbilisi (Georgia) provides a cautionary example of insufficient urban water infrastructure under climate stress. In June 2015, intense rainfall over the Vere River (a tributary of the Kura) triggered catastrophic flash floods and landslides in Tbilisi, resulting in 23 deaths and widespread destruction of homes and city facilities [14]. The disaster was exacerbated by uncontrolled development in the floodplain and an under-capacity drainage system, and it famously led to zoo animals escaping when the zoo was inundated [15]. This tragedy spurred Tbilisi to re-examine its land use and stormwater infrastructure; efforts are now underway with international support (e.g., UNDP) to improve flood preparedness, early warning, and river management in the capital. All three cities—Chișinău, Timișoara, and Tbilisi—share common challenges with Uzhhorod: they are navigating the legacy of Soviet-era or older infrastructure, constrained municipal budgets, and emerging climate extremes. Their experiences underline the importance of an integrated approach that combines engineering upgrades, ecosystem considerations, and, where applicable, cross-border cooperation in water management [16].

The modernization of Uzhhorod’s hydrotechnical infrastructure is situated at the intersection of global climate adaptation needs and the specific context of post-socialist, transboundary cities. This introduction has outlined the broader context of rising climate-induced water risks and the particular deficiencies in urban water infrastructure beyond the EU’s current borders. It has also summarized key technical aspects of the planned upgrades on the Uzh River—including the extent of bank fortification, types of regulatory structures, and environmental safeguards—and highlighted the innovative melding of flood control, ecological restoration, and cross-border governance in the project. The approach in Uzhhorod bridges multiple disciplines and administrative boundaries, representing a novel model for small river cities facing similar predicaments. The following sections will detail the methodology of hydrological and environmental analysis used, present the design and impact evaluation of the proposed measures, and discuss the implications of this case for sustainable water management in comparable regions. Through this case study, we aim to contribute to the growing body of literature on climate-resilient urban water systems in post-socialist and borderland contexts, providing insights that are transferable to cities like Chișinău, Timișoara, Tbilisi, and beyond. To better understand the context of this study, a detailed overview of the urban and hydrological setting of Uzhhorod is provided in the following section.

2. Study Area: Uzhhorod’s Urban and Hydrological Context

We have considered the conditions of the city Uzhhorod, located in the western part of the Transcarpathian region (Ukraine), as the object of research. Uzhhorod serves as the administrative and economic hub of the Transcarpathian region in Ukraine. Historically significant, the city was first mentioned in chronicles as early as 872. It was ruled by Hungary and later by Austria-Hungary Empire. For a long time, it was a fortress of the Druget family. Uzhhorod developed as an industrial and cultural center of Transcarpathia. In 1919, it was the capital of Subcarpathian Rus as part of Czechoslovakia; in 1945, it was transferred to the Ukrainian Soviet Socialist Republic; and since 1991, it has been part of independent Ukraine [17].

Geographically, Uzhhorod is situated along the Uzh River within the Danube basin (105 km within the borders of Ukraine; within the city limits, the river stretches 12.85 km). The Uzh River meanders through the city, dividing it into two parts: the older right-bank sector lies on volcanic hills, while the left-bank areas extend into the Middle Danube Lowland. The river’s floodplain alternates along the banks, varying from 100 to 2500 m in width, while the riverbed measures between 30 and 150 m. Water depth ranges from 0.2 to 2.0 m, and the flow rate averages 0.7 m/s. Seasonal floods, particularly in spring, cause water levels to reach up to 127.57 m above sea level at the city’s entrance and 112.17 m at its exit. The river’s hydrology is further complicated by the presence of small islands, silt deposits, and overgrown vegetation that impairs flood water flow. Groundwater levels in the floodplain occur at depths of 0–2.5 m, while other parts of the city experience seasonal “overflow” groundwater, primarily in autumn and spring [18]. In 1923, planned work began to regulate the flow of the Uzh River within the city of Uzhhorod, which made it possible to free up large areas of swampy land on the right bank for the development of new neighborhoods. The main river was branched off by the Malyi Uzh, a stream that flowed through the center of Uzhhorod. In 1936, the Malyi Uzh was filled in [19].

Figure 1 illustrates the territory of Uzhhorod city as represented by the Normalized Difference Water Index (NDWI). This index is considered particularly effective for identifying water bodies, which typically exhibit NDWI values greater than 0.5. Vegetation, on the other hand, corresponds to lower NDWI values, while built-up areas are characterized by positive NDWI values ranging from zero to 0.2. The map also clearly displays the border with Slovakia, as well as the river Uzh, which flows into Slovak territory [20].

Over the past 100–120 years, the average annual temperature in Uzhhorod has risen by about 1.0 °C. The average annual precipitation in Uzhhorod is 748 mm. The minimum annual precipitation (443 mm) was observed in 1961 and the maximum (1134 mm) in 1980. The maximum daily precipitation (75 mm) was recorded in June 1892. On average, there are 156 days of precipitation in the city per year; the lowest number of days (9) is in October, and the highest number (18) is in December. We can often observe floods in the Uzhhorod during the period of extensive snowmelt in the mountains in spring, which always caused problems not only in the region but also in Slovakia, Hungary, and Romania. Specific climate change on a global scale exacerbates challenges of sustainable river management in climate-stressed border cities, leading to increased frequency and intensity of extreme weather events. Rising temperatures and changing precipitation patterns heighten the risk of spring floods, further stressing the already fragile water infrastructure of the city [21].

Another important reason for hydrotechnical challenges is the urbanization expansion of Uzhhorod caused by war, which exacerbates the city’s existing water management challenges, demanding urgent attention to sustainable and adaptive hydrotechnical solutions. The city’s population of approximately 115,000 people, alongside more than 25,000 internally displaced persons since 2022, creates a dense urban environment. The current area of the city spans 3995.2 hectares, with 76.3% of the territory built up. Residential buildings occupy around 1460 hectares, leaving less than 285.4 m² of territory per citizen. Since 2022, war-driven displacement has intensified urbanization, increasing the strain on Uzhhorod’s water infrastructure. By 2023, construction activity surpassed pre-war levels, nearly tripling, and in 2024, it saw a 24% increase [22].

Modernizing of existing hydrotechnical infrastructure in Uzhhorod requires not only technical upgrades but also the incorporation of circular economy principles: utilizing recycled materials in construction, implementing energy-efficient technologies, and integrating nature-based solutions will enhance both the infrastructure resilience and environmental sustainability of the region. Uzhhorod and border regions face risks such as waterlogging, erosion, landslides, and high groundwater levels, all of which contribute to a highly unstable hydroscape. Addressing these challenges involves adopting adaptive management frameworks that prioritize long-term resilience over short-term fixes [23].

3. Materials and Methods

This study applied a structured methodology to examine both the theoretical and practical dimensions of sustainable river management in climate-stressed border regions. The research approach combined archives and bibliometric analysis, mathematical and physical modeling, comparative evaluations of Ukrainian and EU hydrotechnical solutions, the modified complex matrix method of American ecologist O. Leopold [24], and Harrington’s desirability function [25].

A systematic review of archives and the existing literature was conducted to identify critical research areas, leading institutions, and key contributors within the field of hydrotechnical challenges and adaptation. Using established academic databases such as Web of Science and Scopus, the study focused on peer-reviewed journals, scholarly books, and media articles published from until 2024. Keywords included “hydrotechnical infrastructure”, “climate change adaptation”, “river Uzh”, “transboundary water management”, “drainage systems”, “groundwater management”, “levee systems”, “flood control”, and “river regulation”. Articles were chosen based on their relevance to hydrotechnical challenges in border regions and their contributions to sustainable water management practices. Both English and Ukrainian sources were reviewed to ensure a broad and inclusive dataset.

Remote sensing data were integrated into the analysis to assess land-water interactions and hydrological conditions within Uzhhorod’s territory. Using the EO Browser platform, a map of the city’s terrain was generated. The Normalized Difference Water Index (NDWI), a widely accepted measure for water body detection, was employed to identify and delineate water features. High-resolution satellite imagery and temporal NDWI values provided insights into the distribution and extent of surface water. By comparing these indices to known urban structures and green spaces, the study was able to determine areas most impacted by hydrological changes. These findings informed subsequent stages of analysis, including infrastructure planning and environmental impact assessments [26].

Next, the research included an assessment of service quality standards. By reviewing existing EU regulations and evaluating Ukraine’s capacity to meet these benchmarks, the study explored the feasibility of harmonizing service standards [27]. This involved analyzing potential impacts on citizen satisfaction, logistical reliability, and overall market integration. As hydrotechnical infrastructure is proposed to be in Ukraine, the main regulatory and legal acts were Ukrainian.

An important part of the methodology employed mathematical and physical modeling to verify the feasibility of proposed hydrotechnical solutions in Uzhhorod. Within the framework of the technical and economic feasibility study, a model was developed to simulate the performance of a low-head dam with segmental gates and bottom outlets. The model covered the Uzh River section between Bab’yaka Street and Ankudinova Street bridges. Calibration was performed using flow rates and water levels derived from engineering and hydrological surveys. The modeling confirmed that the proposed hydrotechnical structures would have minimal impact on the river’s overall regime while effectively stabilizing high-erosion areas through reinforced bank protection. This modeling approach provided essential data for finalizing the project design and supported the integration of engineering, ecological, and economic considerations [28].

To enhance the scientific robustness of the study, we employed an integrated analytical framework based on interdisciplinary environmental assessment tools. The methodology combines both structural and process-based evaluations to ensure a comprehensive understanding of hydrotechnical vulnerabilities in the Uzh River basin.

We applied a modified version of the Leopold matrix to assess the ecological and social significance of various project activities, adjusting the matrix to reflect urban hydrological dynamics. This matrix allowed the integration of expert judgment, semi-quantitative impact scales (0–3), and environmental significance ratings across multiple categories (hydrology, biodiversity, landscape, infrastructure risk, etc.).

In parallel, the Harrington desirability function was utilized to evaluate the cumulative environmental impact, including potential accidental events and temporal dimensions (short-, medium-, and long-term consequences). This method enabled us to generate composite scores that informed the sustainability ranking of proposed interventions.

Additionally, spatial analysis tools and available GIS layers were used to inform decision-making about flood-prone areas, sedimentation intensity, and infrastructure vulnerability. Data triangulation was ensured through the use of official reports, stakeholder consultations, and scientific literature relevant to similar urban river systems in Eastern Europe.

Overall, this multi-layered methodology integrates technical modeling, regulatory analysis, geospatial data, and environmental impact assessment in a coherent analytical framework. Such an approach ensures the scientific validity and practical applicability of the findings, providing a transferable methodology for other borderland cities facing similar hydrotechnical and climate-related challenges.

To further clarify the structure of the adopted research methodology and its potential for future application, a comprehensive workflow diagram was developed and is presented in Figure 2.

The diagram illustrates each core methodological step, from bibliometric and geospatial analysis to physical modeling and environmental impact assessment. It also highlights future research directions, including integration of circular economy models, life cycle assessment (LCA), and nature-based solutions (NBS), such as biofilters, riparian green belts, urban wetlands, and phytoremediation techniques. Color-coded elements in the diagram distinguish between the completed stages of the study and those planned for subsequent research phases. This visual representation reinforces the interdisciplinary nature of the study and supports replicability in other climate-exposed urban river contexts.

4. Results

The results outlined in this section highlight critical vulnerabilities in Uzhhorod’s hydrotechnical systems and demonstrate how engineering and ecological interventions can enhance urban resilience in a transboundary context. Particular attention is given to drainage, water supply, and wastewater infrastructure, which have been assessed through technical inspections, spatial analysis, and review of operational records.

4.1. Heading

4.1.1. Urban Drainage Vulnerabilities and Modernization Needs

The hydrotechnical infrastructure of Uzhhorod is centered on two key components. Firstly, a levee and embankment system spans 2.54 km along both banks of the Uzh River, functioning as the principal line of flood defense. Secondly, a 2.14 km long derivation canal, equipped with pumping and filtration stations (CPFS-1, CPFS-2, and CPFS-3), supplies water to the city’s northeastern districts on the right bank.

Despite their strategic importance, both systems demonstrate significant deterioration and insufficient adaptability to current hydrological pressures. The city predominantly relies on a combined sewer system that conveys both stormwater and domestic wastewater. Although a stormwater pumping station was designed by the Giprokummunstroi Institute (Lviv), it was never implemented. Consequently, untreated stormwater is discharged directly into the Uzh River in the absence of dedicated treatment facilities at discharge points [29].

Approximately 25% of the left-bank area operates under a separate sewer system, while the rest of the city remains dependent on the outdated combined model. According to the Department of Municipal Infrastructure, the stormwater drainage network extends 117.2 km, with only 9.2 km consisting of closed pipelines, as shown in Figure 3.

A significant proportion of the drainage system remains open, increasing its vulnerability to siltation and blockages.

Constructed primarily in the 1970s using reinforced concrete, ceramic, and asbestos-cement pipes, the system is now considered a legacy network suffering from hydraulic inefficiency and physical degradation. The system has not undergone systematic structural assessment, but field evidence indicates heavy sedimentation and age-related deterioration. Consequently, it fails to meet contemporary standards for surface water drainage.

Even during dry periods, wastewater treatment plants operate at or near full capacity. During intense precipitation, backpressure in hillside collectors often leads to manhole dislodgement and localized flooding. Additionally, unauthorized private connections exacerbate hydraulic loads and increase pollutant inputs. These challenges are compounded by the absence of sediment traps, drop structures, and effective regulatory enforcement.

A comprehensive modernization strategy is therefore urgently required. This should include regarding pipelines to ensure adequate hydraulic slopes, constructing drop shafts, installing new stormwater inlets and sediment traps, and legally eliminating unauthorized sewer connections. These measures are essential for restoring hydraulic performance and protecting surface water quality in the Uzh River [30].

Similar challenges are faced in other post-socialist cities, such as Chișinău (Moldova), where a Green City Action Plan has been launched to manage combined sewer overflows through a combination of nature-based and grey infrastructure. In Timishoara (Romania), an aging dual-channel system is undergoing phased rehabilitation and the integration of real-time flow monitoring [31]. These cases underscore the broader regional relevance of Uzhhorod’s experience, reinforcing the need for integrated urban water management aligned with EU Water and Flood Directives.

4.1.2. Current State and Optimization Strategies of Uzhhorod’s Water Supply System

Although Uzhhorod’s centralized water supply system ensures sufficient coverage and reliability, infrastructure aging, uneven load distribution, and inefficiencies in water treatment remain critical challenges that call for strategic modernization [32].

The municipal water supply system of Uzhhorod is a critical element of the city’s hydrotechnical infrastructure, ensuring access to potable water for residential, institutional, and industrial users. Designed as a centralized system, it combines domestic drinking water provision with firefighting capacity and is officially classified as Category I according to operational reliability standards.

The water infrastructure is managed by the municipal utility company “Vodokanal of Uzhhorod”, which operates on behalf of the territorial community. In addition to servicing Uzhhorod itself, the system extends water services to several peri-urban villages, including Korytniany, Kinchesh, Chaslivtsi, Mynai, Storozhnytsia, and Onokivtsi.

As of 1 January 2023, the officially declared installed capacities of the water system components are as follows as presented in Figure 4 with a comparative visualization of these capacities and their actual utilization:

• Municipal water supply system: 65,000 m³/day (35% utilized);
• Water intakes: 75,000 m³/day (35% utilized);
• Water treatment facilities: 37,000 m³/day (34% utilized).

As shown in Figure 3, all core elements of the water supply system (intakes, treatment facilities, and distribution) currently operate at only ~34–35% of their installed capacity. The bar chart demonstrates relatively balanced performance across infrastructure components but also underscores the significant unused operational capacity—an opportunity for optimization, especially under future demographic or climatic pressures. The left axis indicates maximum capacity (m³/day); the right axis shows current utilization (%). The graph highlights the underutilization of all three major subsystems, suggesting operational flexibility but also signaling inefficiencies.

Further technical understanding of the water supply system is provided in Figure 5, which illustrates the spatial organization and hydraulic structure of Uzhhorod’s water supply network:

(1) Water intake “Mynai”: 1—water intake facilities (water intake wells) with pumping stations of the first lift; 2—clean water tanks (CWT); 3—pumping stations of the second lift; and 6—water treatment facilities.

(2) Surface water intake (complex of pumping and filtering stations, CPFS-1, since 1929 but reconstructed in 1950; CPFS-2, exploited since 1970; and CPFS-3, exploited since 1987): 5—water intake unit; 4—disinfection unit; 7—water pipelines; 8—water distribution network; and 9—booster pump station [33].

The current state of Uzhhorod’s water supply system is based on official reports from the Municipal Utility Company “Vodokanal of Uzhhorod”, data from the Tisza River Basin Water Resources Management, and information from the updated urban planning documentation titled “Uzhhorod, Transcarpathian Region. Amendments to the General Plan of the City”, Section “Water Supply and Sanitation” (prepared by DIPROMISTO, Kyiv, 2015). Recent data on centralized water supply facilities in Uzhhorod were obtained from statistical reports for 2022, including forms № 11-NKREKP (annual), № 1-Water Supply (annual), and № 2-TP Vodhosp (annual):

2014: A total of 8.66 million m³ of water (23.73 thousand m³ per day) was extracted from natural water bodies, including 4.13 million m³ (11.32 thousand m³ per day) from surface sources and 4.53 million m³ (12.41 thousand m³ per day) from underground sources. Out of this, 5.38 million m³ of water was supplied to all consumers, with 4.55 million m³ allocated to the population and 0.84 million m³ to enterprises, institutions, and organizations for domestic and household needs.

2022: A total of 9.45 million m³ of water was extracted (109% compared to 2014), including 4.54 million m³ from surface sources and 4.91 million m³ from underground sources. In 2022, 5.37 million m³ of water was delivered to all consumers (99.8% compared to 2014), with 4.50 million m³ supplied to the population and 0.87 million m³ to enterprises, institutions, and organizations for domestic and household needs.

The Municipal Utility Company “Vodokanal of Uzhhorod” holds a special water use permit (No. 43/3K/49l-22, dated 30 September 2022) issued by the State Water Resources Agency of Ukraine [34,35,36,37,38,39]. This permit authorizes water abstraction for several purposes, including drinking and sanitary needs, industrial use, water supply to the population, and distribution to secondary water users. Under the terms of this permit, the company withdraws water from both underground sources within the Uzhhorod-Toritsk deposit and a surface water source in the Uzh River within the established limits.

These graphs in Figure 6 highlight the relative predominance of groundwater abstraction over surface intake. While both sources demonstrate stable operation, a moderate reliance on groundwater is evident, which may support higher resilience during surface water shortages.

1. Underground sources: 8363.027 thousand m³ per year (22,912.404 m³ per day).

2. Surface sources: 7778.563 thousand m³ per year (21,311.131 m³ per day).

The abstraction of potable water from underground sources occurs at the Mynai water intake, which is located to the south of the city’s boundary, as well as from a localized water intake within the city limits since 1972. The left diagram shows the annual water intake in thousands of m³. It shows that groundwater sources are used slightly more than surface sources (8363 thousand m³ versus 7779 thousand m³). The right diagram illustrates the average daily water intake. It also shows the advantage of the groundwater source (22,912 m³/day vs. 21,311 m³/day).

4.1.3. Sewage and Wastewater Management System

The centralized wastewater infrastructure in Uzhhorod plays a pivotal role in urban sanitation but is increasingly strained by aging components, hydraulic overload, and operational inefficiencies. As of 1 January 2023, the installed capacity of Uzhhorod’s sewerage system was recorded as follows:

• Sewer network: 100,000 m³/day (utilized at 51% capacity);
• Sewage pumping stations: 100,000 m³/day;
• Sewage treatment facilities: 50,000 m³/day (utilized at 102% capacity).

The city employs a dual system comprising both combined and separate sewer networks. Approximately 75% of the urban area operates on a combined system originally developed in the 1930s, where a single pipeline collects domestic, industrial, and stormwater flows. The municipal sewage treatment facilities (STFs) were constructed in two stages: the first in 1975, with a capacity of 25,000 m³/day, and the second in 1986, doubling the total to 50,000 m³/day. Located in the city’s northwest, the STFs now operate slightly above their design capacity, processing up to 51,080 m³/day.

The treatment process includes mechanical and biological phases. Mechanically, wastewater undergoes screening, grit removal, and sedimentation. Biologically, it is aerated in clarifier tanks with oxygen supplied by blower stations, followed by secondary sedimentation. In 2023, modern sludge dewatering units were installed to improve efficiency and reduce environmental impact [40].

However, effluent is discharged into the Uzh River without disinfection, posing environmental risks. Although a special water use permit regulates discharge, the sanitary protection zones around the infrastructure are only partially maintained [41].

Industrial discharges—largely untreated—enter the municipal sewer system. With the decline of major industries and the rise in domestic pollutants (e.g., detergents), current technologies fail to meet legal thresholds for nitrogen and phosphate compounds [42].

A portion of households remains unconnected to the centralized network, relying on septic tanks or latrines. These unsealed systems pose contamination risks to the groundwater aquifer and lack regulatory oversight [43]. To visualize the performance disparities within wastewater infrastructure components, Figure 7 provides a comparative analysis of capacity and utilization:

Blue bars show installed capacity (m³/day); the red line represents current utilization as a percentage. The stark contrast between sewage treatment plant overload (102%) and underutilized sewer networks (51%) suggests hydraulic mismatch and calls for urgent balancing interventions.

Given these systemic challenges, a set of urgent priorities is identified:

• Critical wear and degradation of WWTF infrastructure;
• Insufficient treatment capacity for both mechanical and biological processes;
• Hydraulic overload during storms (up to 100,000 m³/day inflow);
• Inadequate nutrient removal capacity;
• Absence of effluent disinfection before discharge;
• Lack of real-time monitoring and supervisory control;
• Need for innovative treatment and disinfection technologies;
• The fact that 33% of sewer networks are outdated or in poor condition;
• Energy-inefficient pumping stations;
• Lack of secondary operational pipelines at critical nodes;
• Incomplete sanitary and buffer zone implementation;
• Limited network coverage in peri-urban areas;
• Non-harmonized cost recovery and tariff structures.

These findings highlight the necessity of a comprehensive modernization plan aligned with the EU Urban Wastewater Treatment Directive (91/271/EEC), the Water Framework Directive (2000/60/EC), and the Sustainable Development Goals (SDG 6.3, 6.5, and 11.6) [44,45,46]. Comparative references to other post-socialist cities, such as Bratislava, Koshice, Brașov, Cluj-Napoca, and Chișinău, may enrich future discussions and support alignment with best practices [47].

4.2. Research Perspectives and Adaptive Strategies for Sustainable Hydrotechnical Development

Building on the previous assessment of Uzhhorod’s hydrotechnical infrastructure (Section 4.1.1, Section 4.1.2 and Section 4.1.3), this section outlines comparative European experience and proposed strategies for adaptive, sustainable management within the context of cross-border river basins.

European countries have accumulated a wealth of experience in river management within climate-stressed border regions according to EU directives, including the Water Framework Directive (2000/60/EC) [48], the Floods Directive (2007/60/EC) [49] and the Habitat Directive (92/43/EEC) [50]. These policy frameworks have driven innovations in cross-border cooperation, transboundary river basin management, and the integration of ecological restoration into hydrotechnical planning.

A notable example is the Rhine River Basin [51]. The Danube River Basin [52] exemplifies the advantages of a unified, multilateral approach. These initiatives led efforts to harmonize national strategies, ensuring that floodplain restoration, sediment management, and water quality improvements adhere to EU standards.

Across Europe, successful case studies have emerged in areas such as sediment transport modeling, natural water retention measures (NWRMs), and the use of decision-support tools that integrate hydrological, environmental, and socio-economic data. By employing advanced numerical models and spatial decision support systems, countries have achieved more efficient allocation of resources, improved stakeholder engagement, and long-term sustainability of their river management strategies. The key lessons from these efforts include the importance of early stakeholder involvement, ongoing research and innovation, and robust legal and institutional frameworks that provide a stable foundation for cross-border collaboration [53].

A proposed hydrotechnical construction represents a pivotal solution aimed at mitigating flood risks for Uzhhorod and surrounding communities within the Uzh Basin, which will have a positive influence on the Danube Basin. For sure, that is only one of the project propositions that could improve sustainable river management in climate-stressed border regions. As a foundational step toward realization, the dam project has been included in the HUSKROUA 2014–2020 cross-border cooperation program under the initiative “Joint Actions for Disaster Prevention in the Cross-Border Uzh River Basin (FloodUZH)” [47].

4.2.1. Location of the Planned Intervention: Bozdosh Park Area

The location of the planned activity according to the detailed plan of the city territory approved by the decisions of Uzhhorod City Council No. 349, dated 3 August 2021, and No. 350, dated 3 August 2021, is presented in Figure 8.

Administratively, the planned works are located within the water fund lands—in the floodplain and channel of the Uzh River and the old riverbed of the Uzh River in the territory of the Bozdosh Park in Uzhhorod.

The Bozdosh Park is a monument of local landscape art located on the left bank of the Uzh River on the outskirts of the central part of Uzhhorod and is a part of the water fund. The park was created in 1954 on the territory of 58 hectares and received its status in 1969 (Decision of the Regional Executive Committee No. 414 of 18.11.1969, No. 243 of 25.07.1972. Decision of the Regional Council No. 220 of 26.05.2011). It is bounded by the Slovianska embankment in the south and a bend in the Uzh River on three sides. The name of the park comes from the name of the historical area around it. In 1999, by the decision of the Transcarpathian Regional Executive Committee, an area was allocated for the foundation of a park within the city of Uzhhorod at 5 Bozdosh Road. Bozdosh Park is a local landscape art monument of 50 hectares. In 2000, the municipal enterprise “Bozdosh Culture and Recreation Park” of the Uzhhorod City Council was established. By 2010, three alleys had been built [27].

4.2.2. Objectives and Technical Parameters of the Regulatory Structure

The proposed hydraulic intervention on the Uzh River in Uzhhorod pursues several strategic objectives: enhancing urban flood protection, stabilizing water levels during low-flow periods, improving local microclimatic conditions, and increasing the city’s recreational and tourism potential. In addition to addressing hydrological risks, the project aims to deliver socio-economic co-benefits by generating employment opportunities during the construction phase and expanding urban green–blue infrastructure.

The initiative is expected to improve the ecological status of the Uzh River by facilitating better flow regulation and sediment management, in line with sustainable water resource governance practices. From an urban planning perspective, the intervention is designed to support the multifunctional use of riparian zones and integrate seamlessly with the city’s landscape framework.

The proposed regulatory structure is planned to be implemented in sequential stages according to a clearly defined technical and environmental project roadmap. This approach reflects best practices in hydraulic engineering and climate-adaptive infrastructure planning. A schematic representation of the proposed solution is presented in Figure 9.

The construction of a hydrotechnical structure unit provides for the following:

• A channel-type control structure—low-pressure dam with a surface segmental gate and a two-section lowering valve;
• A fish passage structure;
• A bottom sluice regulator designed to clean the channel from solid sediments;
• An operator’s building on the right bank.

The bank protection and dam construction will not only provide flood protection but also create multifunctional pedestrian transport paths and accessible operational routes. The project includes the reconstruction of the right-bank protection dam (near Studentska embankment), which will help ensure the durability of the infrastructure [54].

The technical and economic feasibility study for the “Construction of a Regulatory Structure on the Uzh River in Uzhhorod (Bozdos Park area), Transcarpathia Region” was carried out. The economic feasibility includes an assessment of the following:

• The project is to construct a regulatory structure on the Uzh River near Bozdos Park to maintain water levels during low-flow periods within the city limits, extending up to the pedestrian bridge near Teatralna Square.
• Protective measures for urban areas, specifically the riverbanks, to mitigate flooding and inundation risks during extreme hydrological events [55].

As part of this economic feasibility study, the following steps and documentation were completed in accordance with Ukrainian legislation and European Union best practices:

• A detailed land use plan (DLUP) was developed following the Ukrainian Law on Urban Development Regulation (Law No. 3038-VI, adopted 17 February 2011) [34].
• A strategic environmental assessment (SEA) was conducted as mandated by the Law on Strategic Environmental Assessment (Law No. 2354-VIII, adopted 20 March 2018) [35].
• A land management plan was prepared in compliance with the Ukrainian Land Code (Law No. 2768-III, adopted 25 October 2001) [36].
• An environmental impact assessment (EIA) was performed in line with the Law on Environmental Impact Assessment (Law No. 2059-VIII, adopted 23 May 2017) [37].

The economic feasibility study also defined the sequential phases of project design and construction:

• Phase 1: Construction of the hydrotechnical node (regulatory structure) on the river Uzh.
• Phase 2: Development of a park zone in the Bozdos Park area.
• Phase 3: Reconstruction of the Uzh riverbanks to protect Uzhhorod’s urban territory from flooding.

The classification of the project’s impact was clarified during the economic feasibility study development. According to relevant Ukrainian standards (Table G.1, Table G.3 of DBN V.2.4-3:2010; DSTU 8855:2019) [38,39], the project corresponds to Class CC 2. The anticipated service life of the structures, as per Clause 2.3.10 of DBN V.2.4-3:2010, is 50 years. Additional geodetic surveys were conducted to refine the planned elevations within the project area. Technical conditions for the project were provided by several regional authorities and organizations, including the State Emergency Service of Ukraine in the Transcarpathia Region, the Transcarpathian Regional State Consumer Service, Transcarpathian Fisheries Protection, Bozdos Park Municipal Enterprise, Vodokanal Municipal Utility, the Transcarpathia Regional Hydrometeorological Center, and the Transcarpathian branch of Ukrtelecom. These technical conditions were issued on 16 April 2021.

To obtain quantitative characteristics of the environmental impacts associated with all phases of the proposed hydrotechnical intervention, a modified complex matrix method was employed. This methodology, originally developed in the early 1970s by American ecologist O. Leopold, is widely recognized for its ability to systematically assess environmental consequences. The approach is structured around a matrix format, where columns correspond to different project implementation stages and activity types, while rows represent environmental factors, such as groundwater resources, aquatic and terrestrial biodiversity, and land use [24].

At the intersection of these parameters, impact significance is denoted using conditional markers, typically assigned numerical values within a predefined evaluation scale. The intensity of environmental effects is rated on a scale from 0 to 3, where 0 signifies negligible or absent impact, while 3 represents a strong, potentially irreversible environmental effect. This structured assessment allows for a comprehensive evaluation of both short-term and long-term environmental consequences, ensuring that the proposed hydrotechnical measures align with sustainable water resource management principles.

The preliminary analysis of the modified complex matrix indicates that the most significant environmental impact of the proposed project will be associated with soil cover disturbance and increased water turbidity. The primary environmental components affected include soil resources, grass cover, and aquatic ecosystems. To assess the level of impact, the following intensity scale was applied:

1 point—low impact;

2 points—moderate impact;

3 points—high impact.

To quantify the cumulative intensity of the planned activities’ impact, the methodology for evaluating impact significance (Σω) was applied. The overall significance of all impacts is determined using the following formula:

γ = 100/n

where n represents the number of significant cells in the matrix (i.e., those reflecting environmental effects that are not equal to zero).

For the presented model in Figure 10, the number of significant cells was n = 85 (considering the probability of accidental events) and n = 61 (excluding such probabilities).

The cumulative impact of the proposed activities was assessed using Harrington’s desirability function, often referred to as the desirability curve, as shown in Figure 11. The calculated overall impact score, considering the probability of accidental events, is 173, which corresponds to a “satisfactory” rating based on the Harrington function. When excluding accident probabilities, the overall impact score is 147, categorized as “very good” according to the same methodology [56,57].

Additionally, it is crucial to consider the duration of environmental impact, which can be classified into three categories: short-term (2–5 years), medium-term (10–15 years), and long-term (50–100 years). Activities related to construction site preparation fall under short-term impacts, while road infrastructure operation contributes to medium-term effects.

Overall, temporary activities associated with project implementation are expected to have the most noticeable environmental impact. However, calculations based on the modified complex matrix indicate that these effects will remain minimal, and even in the event of an accidental disruption, the potential environmental consequences are not expected to pose a significant risk to key ecological components.

5. Discussion

The proposed hydrotechnical infrastructure intervention on the Uzh River offers a timely response to the multifaceted challenges faced by climate-vulnerable, transboundary urban regions. It reflects broader efforts in Europe to modernize hydraulic infrastructure in line with the EU Water Framework Directive, the Floods Directive, and SDG targets 6.3, 6.5, and 11.6, prioritizing resilience, ecological continuity, and public engagement.

5.1. Comparative Analysis with EU Best Practices

The conceptual and technical approaches of the Uzhhorod project demonstrate alignment with successful models across the European Union. In Slovakia, the Váh River Flood Control System has shown the value of combining traditional engineering solutions—such as levees, spillways, and bypasses—with adaptive water regulation and community-inclusive governance [58,59,60]. Similarly, the Hungarian Tisza River Basin Management Program illustrates the effectiveness of integrating grey and green infrastructure, notably through floodplain restoration, natural retention measures (NWRMs), and ecosystem-based water control strategies. These projects were made successful not solely through technical excellence but via robust legal harmonization with EU environmental directives and deliberate public engagement [61,62,63,64,65].

The Uzh River initiative borrows key principles from these models while responding to the specific regulatory and infrastructural context of Ukraine, which is not an EU member but aspires to regulatory approximation. By incorporating adaptive infrastructure, ecological corridors (e.g., fish passages), and sediment regulation systems, the project mirrors EU standards in both form and intent.

5.2. Systemic Resilience and Technical Design Relevance

The infrastructure design includes the following:

• A channel-type regulatory structure with a segmental gate and adjustable valves, enabling responsive flood and low-flow management;
• A fish passage system, ensuring habitat connectivity;
• A bottom sluice mechanism to prevent excessive sedimentation and support water quality maintenance;
• A real-time monitoring facility, enabling adaptive operational control in response to hydrometeorological data;
• Additional dam reinforcement and embankment reconstruction near urban critical points, particularly the Studentska Embankment, to enhance resilience against extreme events.

These technical elements are informed by lessons from both Eastern and Western Europe. Moreover, their integration into the urban fabric—via multifunctional pedestrian and transport paths—demonstrates a shift toward nature-based and socially embedded infrastructure development [66,67,68,69,70,71,72].

5.3. Governance Challenges and the Role of Stakeholder Engagement

Despite receiving technical approval and environmental clearance, the project’s progress has been hindered by inconsistent communication with local communities. This reveals a gap between formal project planning and social license to operate.

Studies across the Danube and Rhine Basin countries consistently emphasize that public participation and transparent decision-making mechanisms increase project acceptance and reduce delays. In particular, the Joint Danube Survey and Floodrisk2020 programs advocate for early-stage consultations and co-design approaches to prevent misalignment between infrastructure objectives and community expectations.

In this context, the Uzh River Project must prioritize the following:

• Developing an open-access platform for sharing project milestones and ecological monitoring data;
• Implementing targeted outreach programs in affected neighborhoods;
• Establishing a participatory monitoring committee, including civil society, environmental experts, and municipal representatives.

5.4. Broader Implications and Policy Relevance

The case of Uzhhorod illustrates the complexities of translating integrated water resources management (IWRM) into practice in non-EU urban territories facing institutional transition, resource constraints, and mounting climate pressures. If successfully implemented, the project could serve as a blueprint for similar post-socialist cities seeking to modernize aging infrastructure in line with EU principles.

Moreover, the use of structured environmental impact methodologies (e.g., Leopold matrix, Harrington’s function) reflects a growing commitment to quantitative and transparent impact evaluation, which is vital for scaling and replicating such models. Importantly, the discussion also highlights the need to institutionalize participatory governance alongside technical excellence to achieve long-term sustainability [73,74].

6. Conclusions

Uzhhorod’s strategic location at the confluence of national and European hydrological networks, combined with its rapid urbanization and climate exposure, makes it a critical testbed for piloting sustainable hydrotechnical solutions in borderland regions. The city exemplifies the multifaceted challenges faced by urban centers located in climate-stressed transboundary basins, including increasing hydrological variability, aging infrastructure, and limited institutional coordination mechanisms.

This study highlights that an integrated, multi-scalar approach to urban water management—involving hydraulic engineering, nature-based solutions, environmental assessment, and participatory governance—is essential for enhancing urban resilience. Specifically, the proposed regulatory structure on the Uzh River demonstrates how context-sensitive engineering can address seasonal water fluctuations, improve flood control, and maintain ecological continuity.

By aligning the design and implementation of this project with EU Water Framework Directive (2000/60/EC) principles and Sustainable Development Goals (notably SDG 6.3 on water quality, SDG 6.5 on integrated water resources management, and SDG 11.6 on sustainable urban development), the Uzhhorod initiative serves as a model for non-EU cities seeking approximation to EU environmental standards. In this context, the project offers broader applicability to other post-socialist and transition cities across Eastern Europe that aim to modernize hydrotechnical infrastructure in line with climate adaptation and circular economy principles.

Moreover, the findings of this study reaffirm the importance of institutional coordination and stakeholder engagement for the success of urban water interventions. Experiences from the Danube and Tisza Basin programs demonstrate that projects embedded in transparent, participatory frameworks have higher success rates in both technical implementation and public acceptance.

Looking forward, further research should aim to carry out the following:

• Explore the long-term performance of hydrotechnical nodes under evolving climate scenarios;
• Evaluate the effectiveness of hybrid governance models combining municipal planning with cross-border river basin management;
• Expand the use of impact-based environmental evaluation tools (e.g., Leopold matrix, Harrington function) to standardize decision making for hydraulic infrastructure in similar urban settings.

In conclusion, Uzhhorod’s experience offers transferable insights for other secondary cities in the EU neighborhood and beyond. As climate pressures intensify, hydrotechnical projects like this must go beyond technical robustness, integrating social, ecological, and institutional dimensions to deliver sustainable and widely supported outcomes.