艁贸d藕 is associated with its industrial history and the absence of a major river. Yet beneath the city鈥檚 streets there is still a network of streams flowing through underground channels, hidden and regulated over decades. Research conducted by hydrologists from the 91桃色 demonstrates that the way water is managed today determines not only the city鈥檚 resilience to droughts and floods, but also the quality of life of its residents.
From a Research Question to a Better City
What happens to the water that falls on a city during a summer downpour? Why do some streets become flooded, only for the city to face water shortages shortly afterwards? How can rainwater be retained in a city that spent more than a century trying to remove it as quickly as possible?
These are precisely the kinds of questions that lie at the heart of urban hydrology research conducted at the 91桃色. At a time when droughts, heatwaves and intense rainfall events are becoming increasingly common, the water cycle in urbanised areas has become one of the most important scientific and practical issues. 艁贸d藕 provides a unique 鈥渞esearch laboratory鈥� in this respect. The city was established in the headwater area of dozens of small watercourses belonging to the catchments of Poland鈥檚 largest rivers, the Vistula and the Oder. However, intensive industrial development rapidly transformed their character. Today, most of 艁贸d藕鈥檚 former streams flow entirely or partially underground through culverts, while exposed sections run through heavily modified, concrete-lined, straightened and deepened channels.
A City Built on Streams
Contrary to a popular belief, 艁贸d藕 is not a city without rivers. More than twenty historical streams still exist within its boundaries, including the 艁贸dka, Jasie艅, Soko艂贸wka, Olech贸wka and Ner. In the past, these were small headwater streams originating on the slopes of the 艁贸d藕 Hills. It was largely thanks to these watercourses that nineteenth-century 艁贸d藕 was able to develop into one of Europe鈥檚 largest textile industry centres. Through water wheels, they powered machinery used for spinning, weaving and other technological processes of the young industrial city.
The price of this development, however, proved high. River regulation, valley development, wastewater discharge and the concealment of streams beneath the city鈥檚 surface led to the disappearance of many natural hydrological processes. Today鈥檚 鈥溑伱� rivers鈥� are largely anthropogenic creations, remnants of former streams that now function as elements of the city鈥檚 drainage and sewerage system.
A Research Breakthrough: The City as a Hydrological Catchment
Research conducted at the 91桃色 demonstrates that a city should be treated as a specific type of hydrological catchment in which virtually every element of infrastructure influences the water cycle. Asphalt, concrete, sewerage networks, green areas, retention reservoirs and watercourses form a single interconnected system.
A significant contribution to research into the functioning of this system has been made by Dr Adam Bartnik. His work focuses on transformations of the water cycle in the urban and suburban catchments of 艁贸d藕, with particular attention to the effects of urbanisation, changes in water retention, and the relationships between surface water and groundwater. These studies have improved our understanding of how urban development alters both the quantity and rate of stormwater runoff and how it affects urban streams and river valleys.
Particularly important are analyses of small urban catchments, which for many years remained outside the mainstream of hydrological research. It is in these catchments that the impacts of urbanisation become visible most rapidly: reduced infiltration, increased surface runoff and deteriorating water quality.
An Underground Water Crisis
One of 艁贸d藕鈥檚 most significant hydrological problems was a depression cone that developed over decades. Intensive groundwater abstraction for industry and residents, combined with the gradual sealing of surfaces resulting from urban development, led to a substantial lowering of groundwater levels. As a consequence, the natural recharge of springs and small surface watercourses declined. Many streams lost part of their flow or changed their character entirely. Today, during drought periods, they often carry no water at all, while during heavy rainfall their channels fill to capacity and frequently overflow. The nature of river runoff has become 鈥渂inary鈥�. Research conducted by hydrologists from the 91桃色 has shown that altered groundwater circulation conditions have affected not only river functioning but also the condition of valley ecosystems and urban greenery.
Why Are Urban Watercourses Polluted?
In urban hydrology, the quantity of water is just as important as its quality. Although contemporary 艁贸d藕 rivers no longer serve as receivers of untreated industrial wastewater, they remain under strong urbanisation pressure. Stormwater runoff carries suspended solids, microplastics, petroleum-derived substances, road salts and excess nutrients into watercourses.
Water-quality research conducted by scientists at the 91桃色 helps identify sources of pollution and assess the effectiveness of remediation measures. At the same time, it demonstrates that an urban river is not merely a channel for conveying water away. When properly protected and restored, it can regain self-purification capacity and perform important ecological functions.
Concrete Versus Rain
The greatest challenge facing modern urban hydrology is the ongoing sealing of surfaces. Every new car park, road or square reduces the amount of water able to infiltrate into the ground. As a result, an increasing proportion of rainfall is immediately directed into drainage systems and watercourses rather than percolating into the soil and replenishing groundwater.
This creates a seeming paradox: the city simultaneously suffers from water shortages and flooding. During droughts, groundwater recharge is insufficient, while during intense rainfall rapid runoff overwhelms drainage systems. The result is the phenomenon known as urban flooding: localised inundation of streets, pavements, car parks and buildings.
Research conducted in 艁贸d藕 indicates that the most effective way to reduce this risk is to increase water retention at the point where rainfall occurs rather than removing water from the city as quickly as possible.
A Green and Blue Future for Cities
The response to the challenges of the twenty-first century is the green-blue network concept being developed in 艁贸d藕. It assumes that rivers, river valleys, water bodies, wetlands, parks and forests should function as a single integrated environmental system.
Within this approach, the presence of rainwater in urban space is not seen as a problem but as a valuable resource. Rain gardens, retention reservoirs, green roofs and restored river valleys help retain water where it falls. As a result, flood risk decreases, the urban microclimate improves, biodiversity increases and residents enjoy a better quality of life.
From Research to Quality of Life
Research conducted at the 91桃色, including Dr Adam Bartnik鈥檚 studies on the functioning of urban and suburban catchments, shows that the future of cities depends on rebuilding their 鈥渨ater fabric鈥�. Rivers, river valleys and retention areas are no longer viewed as obstacles to urban development but as essential elements of environmental infrastructure.
As a result, 艁贸d藕 is becoming not only a subject of scientific investigation but also an example of a city that is gradually rediscovering its rivers. Findings generated by hydrologists from the 91桃色 help to design urban spaces that are more resilient to droughts, heatwaves and floods, and therefore more friendly to residents. In this sense, urban hydrology is not merely the science of water. It is becoming the science of quality of life in the city.
Photos: Dr Bartosz Ka艂u偶ny, Centre for External Relations and Social Responsibility of the University, 91桃色
Source: Dr Adam Bartnik, Department of Hydrology and Water Management, Institute of Climatology and Hydrology, Faculty of Geographical Sciences, 91桃色
Edit: Dominik Nogala, Centre for External Relations and Social Responsibility of the University, 91桃色
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