Choked Yamuna fuels vector disease worries in Delhi

A senior official with MCD’s public health department said that the enclosed cup-like space at the centre of the water hyacinth leaves collects rainwater

The 2-3km stretch of the Yamuna along the Okhla barrage in southeast Delhi is currently covered with a thick layer of water hyacinth (Eichhornia crassipes). This water weed is not only deteriorating the already sub-standard water quality of the river, but also acts as a potential breeding ground for mosquitoes, which may lead to a rise in vector-borne diseases, senior Municipal Corporation of Delhi (MCD) officials said.

The Yamuna filled with water hyacinth at Kalindi Kunj, as seen on July 18. (Sunil Ghosh/HT photo)

A senior official with MCD’s public health department said that the enclosed cup-like space at the centre of the water hyacinth leaves collects rainwater.

“This water serves as ideal breeding ground for the Aedes aegypti, which breeds only in fresh water. Insecticide sprayed from our pumps cannot cover the areas inside the river channel, and the only solution is to weed out the water hyacinth,” the official said, requesting anonymity.

According to the official, the Okhla barrage is under the jurisdiction of the Uttar Pradesh government, and MCD has sent letters to the neighbouring state to remove the weed from the river.

“We have asked the UP irrigation department to expedite the clean-up. The dense bed also prevents the insecticides to reach the water surface,” the official said.

A second MCD official said thick beds of water hyacinth are known to reduce the velocity of water bodies, thereby serving as suitable breeding grounds for mosquitoes.

“So far, there has not been much rain in this part of Delhi, so the mosquito breeding levels have remained low. However, the water hyacinth needs to be cleared, otherwise it may spell trouble for nearby southeast Delhi areas,” the second official said, adding that the areas which may be impacted include Okhla, Kalindi Kunj, Sarita Vihar, Jasola Vihar, Madanpur Khadar, Jamia Millia Islamia, and Abul Fazal Enclave.

Aedes aegypti can spread dengue fever, chikungunya and yellow fever. It lays eggs in clean water and has adapted to breed among human dwellings.

An analysis of MCD data on mosquito breeding sites from 2022 reveals that around 58.5% of Aedes aegypti larvae were found in water storage units such as drums, buckets, and jerrycans; 30.2% in peri-domestic units such as money plant vases, flower pots and bird pots; while overhead tanks accounted for 5.4%, sumps for 2.1%, and desert coolers for 3.8% of all breeding sites.

In 2023, Delhi recorded 9,266 dengue cases and 19 deaths — the third-worst outbreak of the viral infection in the city, according to MCD’s annual data.

This year, Delhi has reported 246 dengue cases in the first six months — double the number of cases reported in the corresponding period in 2023, and the highest in at least last decade. The city had reported 122 dengue cases between January 1 and July 1 in 2023, 143 cases in same period in 2022, 36 cases in 2021, and 20 cases in 2020.