Dip in Delhi’s blue cover amid urbanisation, increase in built-up area, study finds

The blue cover in Delhi fell by around 14 sq km in about 20 km from the city centre and by around 23 sq km in 20 to 50 km from the city centre when data from two study periods, 1998 to 2002 and 2013 to 2017 is considered, according to the study ‘Urban Blue-Green Conundrum: A 10-city study on the impacts of urbanisation on natural infrastructure in India’.

The study used remote sensing data and satellite imagery to monitor urbanisation and changes in blue-green infrastructure between 2000 and 2015 in 10 cities – Ahmedabad, Bengaluru, Chennai, Delhi, Hyderabad, Jaipur, Kolkata, Mumbai, Pune and Surat. This was studied in two spatial intervals of 0 to 20 km from the city centre and 20 to 50 km from the city centre.

In Delhi, in the 0 to 20 km region, blue cover decreased from 36 sq km during 1998-2002 to 22 sq km in 2013-2017. In the 20 km to 50 km region, it has decreased from 67 sq km in the 1998-2002 period, to 44 sq km in the 2013-2017 period.

Subscriber Only Stories

View All

UPSC Key- February 6, 2023: Know and Understand Guaranteed Pension Scheme...

Amartya Sen interview: ‘The Santiniketan of Satyajit Ray, Nandalal Bose …...

UPSC Essentials | Key terms of past week with MCQs

ExplainSpeaking | Budget 2023-24: Economic growth, fiscal health and unem...

Monthly plan to access Budget

Meanwhile, the built-up area in Delhi has increased. In the 0 to 20 km region, it has increased from 707 sq km in 2000 to 858 sq km in 2015.

The study by Sahana Goswami, Samrat Basak, Aakash Malik and Raj Bhagat Palanichamy noted that “urbanisation is seen as one of the key modifiers of blue cover”.

“The replacement of natural surfaces, water bodies, agricultural lands, vegetation, and forested lands with built-up area such as buildings, pavements, and roads alter the hydrological characteristics of urban areas, leading to changes in stormwater runoff, evapotranspiration, and infiltration and reduces local water (both surface water and groundwater) availability,” it stated.

The study indicated that a blue cover reduction was observed due to either a decrease in the extent of water in the water bodies that were observed or encroachments into the water bodies.

It noted: “…the 10 largest metropolitan areas in India increased their built footprint by 52 per cent (in the 0–50 km region) between 2000 and 2015 at the expense of their surface water bodies and high groundwater recharge zones. The lost surface water bodies and groundwater diverted away from aquifers could have provided water to meet the needs of a fifth to half of the new urban population added to these cities in the study period. These biophysical disruptions will eventually have social and economic impacts on urban dwellers and regions, such as increased water scarcity, loss to life and property due to urban floods, heat-stress-induced risk to health and reduced productivity, and increased costs to urban water utilities for supplying water from distant sources.”