Dhaka, the overburdened capital city of Bangladesh, faces severe water management challenges, such as flood and waterlogging, especially during the monsoon season. The concept of a Sponge City offers a promising solution to combat these issues. This article delves into the details of the Sponge City concept, its successful implementation in other countries, and why it should be adopted in Dhaka. The Concept of Sponge City Kongjian Yu, a Chinese landscape architect and professor, pioneered the concept of the Sponge City. A Sponge City is designed to passively absorb, clean, and utilize rainwater in an eco-friendly manner by reducing polluted runoff. Essentially, it uses landscapes and infrastructure to preserve water and promote natural retention, infiltration, and purification of drainage. Key techniques associated with a Sponge City include: ·        Rainwater Harvesting: Collecting and storing rainwater for various uses. ·        Permeable Roads: Roads designed to allow water to seep through and be absorbed into the ground. ·        Terrace Gardens: Green roofs that help absorb rainwater and reduce runoff. ·        Green Spaces and Waterbodies: Parks, ponds, and lakes that act as natural water retention and purification systems. Proper implementation of these techniques can minimize the frequency and severity of floods, improve water quality, and reduce individual water usage. Green roofs, for example, enhance the quality of life by improving air quality and mitigating urban heat islands. Overall, a Sponge City can efficiently handle excess water during heavy rains and reuse it during dry periods to combat water shortages. Read more: How to Build Dhaka as a Water Wise City How China Adopted the Concept of Sponge City In 2013, the Chinese Central Government adopted Professor Kongjian Yu’s Sponge City concept, implementing it across 30 cities. Following successful trials, China aims to transform 80% of urban areas into “sponges” by 2030. The core principle of Chinese Sponge Cities is to give water enough room and time to drain into the soil rather than quickly channeling it into large dams. Instead of fast-flowing water channels, these cities employ meandering streams without concrete walls, allowing water to spread out during heavy rains. Yu asserts that replacing concrete infrastructure with natural systems can save lives. In Sponge City designs, natural waterways and permeable soils clean water and reduce pollution. Evaporated rainwater cools the city, while collected rainwater is used for irrigation, street cleaning, and other purposes, reducing the reliance on tap water. The vegetation, sediments, and microorganisms in Sponge City water systems lessen the burden on energy-intensive urban water filtration facilities. As climate change brings unpredictable rainfall, Sponge City buildings are constructed to accommodate rising water levels during floods. Compared to traditional gray infrastructure, Sponge City designs require less energy for maintenance. They reduce the load on water treatment facilities, decrease the need for air conditioning due to heat reduction effects, and use fewer resources like concrete. Additionally, vast green spaces absorb carbon dioxide and air pollutants, promote biodiversity, and provide recreational areas for residents. China has also implemented Sponge City concepts in Ningbo, a coastal city 150 km south of Shanghai. Ningbo’s sponge infrastructure includes an eco-corridor on a post-industrial site, where channeled water flows through meandering waterways surrounded by native plants. This blue space improves water quality, provides habitat for flora and fauna, and reduces the risk of waterlogging. Read more: What Can Dhaka Learn from the Smart City Singapore Application of Sponge City Model in Copenhagen Copenhagen adopted the Sponge City concept in its Cloudburst Master Plan, developed in 2012. This plan redesigns approximately 250 public spaces to retain or redirect floodwaters, including parks, playgrounds, and the Sankt Kjelds Plads roundabout. Green spaces like trees, shrubs, and soil naturally retain water and direct it to non-destructive areas.

Prime Minister Sheikh Hasina on Wednesday stressed the need for rainwater harvesting and river water conservation instead of its collection from the underground. “We’ll have to harvest rainwater and conserve river water in the rainy season anyhow so that we can use the water properly,” she said while opening the newly constructed Sheikh Hasina Water Treatment Plant-II of Chattogram Wasa. The prime minister joined the function virtually from her official residence Ganobhaban here. The programme was held at a hotel  in Chattogram. Read: President calls for more US investment in Bangladesh The new plant will raise overall water supply capacity of Chittagong Wasa to 50 crore liters a day, an increase by 14.30 crore liters. The plant has been constructed at Rangunia in Chittagong under Chattogram WASA Karnaphuli Water Supply Project (Phase-II). Hasina said water reservoirs should be kept in every place in case of construction of any structure, no matter if it is housing or industrial one, in order to harvest rainwater and conserve river water during the rainy season. “We’ll have to bring down our dependency on underground water,” she said, adding that her government constructed the water treatment plant based on surface water. “Since the water treatment plants are now collecting water from the surface sources, our dependency on underground water is declining,” she said. LGRD and Cooperatives Minister Md Tazul Islam and Mayor of Chattogram City Corporation Md Rezaul Karim Chowdhury also spoke at the function, while Information and Broadcasting Minister Hasan Mahmud was present at Chattogram end. Senior Secretary of Local Government Division Helal Uddin Ahmed conducted the virtual event and Managing Director of Chattogram Wasa Engineer AKM Fazlullah delivered the welcome speech.

The RIBA International Prize 2021 is given to a hospital in Bangladesh's Satkhira district for being the world's greatest new structure. The Friendship hospital is a paradigm of climate-conscious architecture created with the lowest minimum of resources. It triumphed over competition from a David Chipperfield-designed museum in Berlin and a Wilkinson Eyre-designed cycling and footbridge in Denmark. The RIBA International Prize 2021 winner drew inspiration from water. The canal winds across the property, gathering important rainfall and aiding in the cooling of the adjacent courtyards during the scorching summer months. It acts as a hurdle between the inpatient and outpatient sections, segregating the two halves of the site without the need for a dividing wall. Conceptual and Designing Aspects When Cyclone Sidr struck the nation in 2007, causing an ever-changing terrain due to increasing water levels, the narrative for this corner of the globe shifted dramatically. Due to constant climate change, seawater has infiltrated the interior, causing all adjacent agricultural lands to be turned into shrimp production ponds. Read Top 10 Historical Mosques in Bangladesh The land around the Friendship hospital was once covered with grain fields. The surrounding settlement was also precarious, consisting mostly of low-rise buildings and thatch homes. Recognizing the limits, the Bangladeshi architect designed a somewhat linear plan with interconnecting courtyards and covered pathways to divide the inpatient and outpatient zones. When it came to establishing access control between these locations, he created a rainwater collection canal that crisscrossed the site's center. This feature operates in a variety of ways. On a functional level, the captured water assists in microclimate cooling and provides a vital resource in a location where salty water is useless for the majority of functions. On an aesthetic level, the property's constant presence of water animates the inside environment and imparts a feeling of visual continuity. A Project of Collaboration "Water pervades this space," explains architect Kashef Chowdhury, head of Urbana, the Dhaka-based firm that designed the building. "However, it is not necessarily of the beneficial kind." Rising sea levels as a result of the climate catastrophe have changed the surrounding landscape of grain fields into shrimp fishery, while the groundwater has become too salty for most uses. Read Perks of being a Miss Universe: Rewards for the Excellence in ‘Beauty with Brain’ Locals make every effort to gather and save every last drop of freshwater during the rainy season. Chowdhury has built the building as a rainwater harvesting machine, with every roof and courtyard surface emptying into the central canal, which connects to two storage tanks at the site's ends. It is the organization's first "land hospital," since Chowdhury previously assisted in converting many boats into floating hospitals to serve rural villages in the delta area. Built on the lowest budget of just under $2 million, its first permanent structure serves as a lifeline for thousands of people in a region devastated by a destructive hurricane in 2007. A Mesmerizing Building with Unique Perks The Grand Jury for the coveted prize, which included prominent people such as Es Devlin, Jeanne Gang, Rossana Hu, and Gustavo Strabo, as well as Decq, thought it pleasant to see a hospital with such a kind and natural touch. "The Friendship Hospital is particularly timely at this point in history since it tackles the global problem of uneven access to healthcare," an official press statement noted, adding that the winning project was also named the world's greatest new building. Read Ancient Temples of Bangladesh: Remembering Their Past Glory "It is an example of how a beautiful building can be accomplished via strong design even when dealing with a limited budget and constrained contextual conditions. This hospital is a celebration of a human-centered structure." Architect Kashef Chowdhary, whose practice is rooted in history and places a premium on climate, materials, and context, discusses winning the award, "In a sublimely significant moment, the RIBA and the jurors have identified a project from the global periphery to elevate to the center of architectural discourse and become the subject of one of the most prestigious global awards." I am pleased that this may motivate more of us to commit to an architecture of care for mankind and the environment, not in spite of, but precisely because of, resource and means constraints, in order to jointly address the global urges we confront; today." Cultural Acceptability Rainwater collecting is a widely acknowledged method of augmenting freshwater supplies in southern Bangladesh. While rainwater collected from ground catchments has a low bacteriological quality, rainwater collected from well-maintained rooftop catchment systems fitted with tight storages and taps is typically good for consumption and often satisfies WHO drinking water criteria. This water is of greater quality than that available in the majority of the world's conventional water sources. Read: Gender Dichotomy: Woketopian Impact on Human Lifestyle Rooftop rainwater collection may produce excellent quality water that is safe to drink if the rooftop is clean, impermeable, constructed of non-toxic materials, and is positioned away from overhanging trees. Sustainability Rainwater collection is one of the most promising options for meeting rising water shortages and demand. The strain on water resources, the increasing environmental effect of huge projects, and worsening water quality all limit the capacity of conventional sources to supply the demand for freshwater. Rainwater collection enables the supplementation of water sources while also promoting self-sufficiency and sustainability. Conclusion Rainwater harvesting effectiveness is determined by the materials used, the design and construction, the maintenance, and the overall quantity of rainfall. The runoff coefficient, which is the proportion of precipitation that occurs as runoff, is a frequently cited efficiency measure of 0.8. By contrast, when cement tiles are utilized as a roofing material, the year-round runoff coefficient is around 75%, but clay tiles often collect less than 50%, depending on the harvesting mechanism employed. Plastic and metal sheets perform the best, with an efficiency of 80–90%. A well-designed and meticulously built gutter system are also critical for the proper functioning of a rainwater harvesting system. If the gutter and down-pipe system are installed and maintained correctly, 90% or more of the rainwater collected on the roof will be discharged to the storage tank. Read 'Sisimpur' nominated for International Kidscreen Awards