Benjamin Franklin says “When the well’s dry, we know the worth of water.” This seems very true for many urban areas and cities in the world.
The mega city Dhaka is experiencing a severe water crisis in recent years. Water shortage becomes worse during the summer months. The groundwater table is diminishing at an alarming rate. Is it too late to achieve water sustainability in Dhaka?
Groundwater Depletion Scenario in Dhaka
At present, Dhaka has around 21 million people, which is projected to cross 32 million by 2035. Uncontrolled migration and rapid urbanisation are generating diverse problems, including the water crisis.
Dhaka Water Supply and Sewerage Authority (Wasa) is failing to supply water to fulfil the demand of residents in half of the areas of the capital city of Bangladesh.
Dhaka WASA’s 2018-19 year’s annual report shows that the daily water demand of Dhaka city is about 2.45 billion litres and 78% of this demand is met by groundwater extraction. Besides these, thousands of private deep tube wells are used in the city to extract water from the underground aquifers. Then surface water sources like rivers and lakes are used to fulfil the remaining 22% demand of water.
Most of The rivers and water bodies in and around the capital city including Turag, Dhaleswari, Buriganga, Tongi Khal, Balu, Shitalakshya, Bangshi River, etc are highly polluted by waste materials disposed of industrial as well as municipal sources. This situation aggravates during the dry seasons.
At present, Dhaka WASA has four plants for treating water. But the amount of treated water is quite insufficient compared with the total demand of water.
The long-term dependency on the underground aquifers has taken a toll on the city’s groundwater table. According to 2030 Water Resources Group, Dhaka’s groundwater table is declining at a rate of 3 metres every year.
If the demand for water increases at the present rate, which is likely, then the projected yearly depletion rate of groundwater reserves can reach up to 5.1 metres by 2030. Currently, the average depth of Dhaka’s groundwater table is about 78 metres, which may sink down to 132 metres in the next 10 to 12 years. Without appropriate preventive measures, the groundwater table may plunge to 100 to 150 metres by the year of 2050.
Multifarious Effects of Water Crisis
The depletion of underground water levels can affect the residential, commercial and industrial zones of Dhaka city.
The unregulated use of groundwater, may lead to severe shortfall in the supply of drinking water from underground aquifers.
When the groundwater table declines, the upper aquifers may run out of water, especially in the dry seasons. This will likely affect the industrial zones around Dhaka including Savar, Ashulia, Tongi and Narayanganj.
The reduction of groundwater level by a certain depth may enhance the risk of earthquakes. An earthquake of 7.0 magnitude can cause massive destruction of human lives and properties in Dhaka city. Fortunately, the probability of severe earthquakes in and around Dhaka is low, due to its unique geological characteristics.
However, the rapid declination of groundwater tables may cause irreversible environmental degradation such as widespread land subsidence which may hamper the natural recharge process of underground aquifers.
Some Exemplary Water Conservation Practices by Cities
According to World Bank data, around 4.4 billion people live in urban areas and cities, which is about 56% of the world’s total population. If this trend continues, the urban population size will more than double by 2050. At this point about 7 out of 10 people will be the residents of urban areas and cities.
Due to the ever increasing pressure of population the water problems in metropolitan cities are more crucial. To tackle the water crisis, different cities around the world are taking innovative measures to manage, protect and conserve water resources.
India’s Bangalore City Protected Lakes from Grabbers
Inhabited by around 10 million people, Banglore, the capital of Karnataka State is the 3rd most populous city in India. About 450 lakes of the city fell under the threat of privatisation and unsustainable use of water in 2010.
These surface water sources contribute to recharge the underground aquifers that supply water to the neighbourhood wells throughout the region. Therefore, drops in the water levels of lakes may lead to drying up of wells.
The project of rehabilitating 450 lakes recharged the underground aquifers. As a result, surrounding communities got adequate quantities of quality water. The farmers produced more yields. In 2012, Bangalore won a UN award for best water management initiative.
South Africa’s Cape Town City Saved Water Massively
Cape Town has got global appreciation for its efforts for saving water resources at a massive scale and managing it efficiently. The city has reduced water consumption by 30%, coping with a 30% population increase over the past 15 years.
To reduce wastage, the city took several initiatives such as controlling water pressure, replacing old pipes, improving leak detection, carrying extensive repairs, efficient management of water metres, training people about water conservation, irrigating with treated effluent instead of potable water, etc.
Brazil’s Sorocaba City Cleaned Up Polluted Rivers
Sorocaba city took initiatives for cleaning up rivers that were badly polluted by the wastage of industrial, mining and sewage sources. In June 2015, residents of the city removed about 228 kg of rubbish from the Sorocaba river in a single day. In a month, the city workers regularly removed about 10 tonnes of wastes including dirt, leaves, branches, rubbish and recyclables from the Sorocaba river.
The city created linear parks along the river bank. Besides enhancing the beauty of the surrounding areas, the parks provided a habitat for wildlife, recreational space for city residents and served as a natural barrier against high tides.
How to Conserve Water in Dhaka City
Now it is the high time for citizens and the authorities of Dhaka city, to reduce pressure on groundwater levels. Here are some ways to preserve water.
The most efficient way to conserve water is using it more than once. Around 75% of water used for domestic purposes can be reused as greywater or waste-free recycled water.
Research shows that toilets account for about 30% of indoor domestic water consumption. Used waters from air conditioners, sinks, showers, and dishwashers, can be routed to the toilet flush instead of clean water.
The multi-use of water approach can also be used for gardening, irrigating, and landscaping, as these uses don’t require drinking-quality water.
Measure Water Usage
Many people tend to waste water or over use of water due to lack of awareness. Knowing one’s own consumption pattern can help one be more conscious about water use.
Through an efficient water metering system with intelligent sensors, city residents can better understand the quantity and pattern of water use, both indoors and outdoors.
In simple words, more precise data regarding water consumption can help better water conservation.
The process of rainwater and stormwater harvesting refers to interception of the storm-water runoff and utilisation of the collected water for other purposes.
Dhaka’s annual average rainfall is about 1,854 millimetres (73.0 in). And, 80% of this rainfall occurs during the monsoon season that lasts from May to September.
Rainwater harvesting can minimise the risks of choking storm drains, and prevent flooding or water logging on roads of Dhaka city. It can reduce the pressure of water-demand on Dhaka WASA and save electricity used for pumping water. Furthermore, the harvested rainwater can fulfil the domestic water requirements.
As Dhaka city experiences high amounts of monsoon rainfall every year, rainwater harvesting systems can be implemented on households, structures, buildings and open areas through watershed management. This supplementary option can reduce pressure on the groundwater table of Dhaka city.
Zero Liquid Discharge (ZLD)
Efficient water treatment systems should be enforced in the industries and factories to prevent river water pollution. For instance, the Zero-liquid discharge (ZLD) process can purify and recycle industrial wastewater. It is an advanced wastewater treatment process that includes steps such as ultrafiltration, reverse osmosis, evaporation, or crystallisation, fractional electrodeionization, etc.
Ways to Build a Water Smart City
An efficient digital water system can integrate the processes of water collection from different sources, water treatment, water storage, water distribution among consumers (domestic, commercial and industrial), and reuse of water.
Such advanced water management systems can utilise cutting edge technologies such as smart metering and intelligent sensors to collect and manage water related data (like measuring water flow and water pressure).
Water Wise System
As a Digital Water solution, Water Wise System focuses on the integral management of the water cycle. It can implement a smart water network that
– reduces cost and enhances operational efficiency by monitoring through sensors, devices, and automation.
– transforming water network’s data into knowledge, through Artificial Intelligence, Machine Learning and Deep Learning to give a holistic view.
– facilitates in responding service interruptions, and system failures.
– prevent water wastage
– solve communication problems
– balances the demand-supply of water
– manages the pressure and flow of water
– controls water quality.
The Digital Water linked to the Water Wise System enters the paradigm of Smart Cities. The concept of Water Smart City is connected with two key factors: urbanisation and the technological revolution.
To build Dhaka as a water wise city proper water conservation measures should be taken in residential, commercial and industrial levels. Efficient methods like rainwater harvesting, greywater recycling, water metering, wastewater treatment, repairing faulty systems, etc can save water and reduce the pressure for groundwater extraction. Motivating residents to minimise water use, and implementation of the latest water management technologies can help Dhaka to achieve water sustainability in near future.
Rifat Tabassam is Postgraduate in Urban and Regional Planning, Jahangirnagar University