Tubewells deplete groundwater as ponds vanish in Ctg

Tula Pukur, a pond excavated in 1822 in Lalkhan Bazar area of Chattogram city, was gradually filled up after 2000 to construct multi-storey buildings, robbing thousands of residents of the area of their main source of water.

Consequently, these people became dependent on deep tubewells for water supply, depleting groundwater in the area.

Like Tula Pukur, around 24,000 ponds and reservoirs have disappeared in the last four decades in Chattogram, increasing people's dependence on groundwater.  Consequently, the continuous fall of the groundwater level is threatening an increase in natural disasters and destruction of biodiversity in the area, said environmentalists.

According to statistics of the Department of Environment in 1981, there were about 25,000 ponds and reservoirs in Chattogram.

But there were only 1,249 waterbodies in the city in 2017, according to a study, "Spatial and Temporal changes in Wetlands of Chattogram Metropolis," by Morshed Hossan Molla, a PhD researcher at Chittagong University.

Among famous ponds and lakes filled by waterbody grabbers are Dewanji Pukur, Raja Pukur, Rather Pukur, Maulvi Pukur, Minamar Dighi, Ramahammad Khan Dighi, Kamaldah Dighi, Colonel Dighi, Cornelhat Dighi, Hazarir Dighi, Damma Pukur, Karbala Pukur, Kazir Dighi, Padma Dighi, and Maillar Pukur.

According to the Bangladesh Environment Conservation Act, 1995 (Amended 2010), filling up any type of reservoir – government or privately owned – is prohibited. Yet the filling and occupation is not stopping in the area, alleged the local people.

Regarding the matter, Mofidul Alam, director of the Department of Environment, Chattogram region, told The Business Standard, "We have a manpower crisis, but still we are working to protect the environment. However, people do not welcome this kind of work."

Morshed Hossan Mollah, who has been researching the city's ponds and reservoirs for over a decade, said, "We found out during our research that the number of reservoirs is declining at a rate of 10% per year, but the actual rate of decline is higher."

"The rate of reduction in pond numbers in our research was low, because some ponds have been created recently in the vicinity of the Outer Ring Road, when soil was dug up for constructing it," he said.

With the decrease in the number of reservoirs, the number of tubewells in Chattogram has increased in the past decades. According to Chattogram Wasa, the number of licensed tubewells in the city was only 60 in 2000, which increased to 4,237 till 25 February this year.

Apart from this, there are more than 50,000 unlicensed tubewells in the city, said an official of Chattogram Wasa on condition of anonymity.

Increased reliance on tubewells has caused a fall in the groundwater level in the city.

According to Chattogram Wasa, the groundwater level in the Agrabad area dropped from 241 feet in 2011 to 312 feet in 2021. In the Pahartali area of the city it dropped from 136 feet in 2011 to 274.6 feet in 2021.

The groundwater level in the Khulshi area was 220 feet below the surface in 2011, which dropped to 345 feet in 2021. In the Bayezid area it was 155 feet below the surface in 2011 and came down to 198 feet in 2021.

Chattogram Wasa Chief Engineer Maksud Alam told TBS, "The reliance on groundwater has increased due to a decrease in the number of reservoirs. So we are trying to meet the demand with surface water, keeping in mind the preservation of biodiversity."

He said Chattogram Wasa currently produces 50 crore litres of water per day. It produced 12 crore litres in 2009.

Various effects of groundwater depletion

When the water level goes down, a hollow space is created under the ground, increasing the risk of natural disasters and destruction of biodiversity. This in turn increases the possibility of damage caused by earthquakes, said Morshed Hossan Mollah.

"The decrease in the number of reservoirs is also responsible for the rise in temperature in the city as waterbodies keep the surrounding areas cool," he said.

The researcher said lakes and ponds also contribute to an increase in groundwater level. When it rains, some of it flows along the land surface to streams, rivers or lakes, while some moisturises the ground. After the soil absorbs sufficient water, excess water accumulates underground.

Dr Muhammed Forruq Rahman, manager (Research and Advocacy) of Network on Climate Change in Bangladesh, said the Intergovernmental Panel on Climate Change (IPCC), a UN body, has mentioned in its latest report that the rise in temperature in Bangladesh can cause an increase in the frequency of natural disasters. One of the reasons for this warming is the filling up of waterbodies.