As per the National Disaster Management Authority (NDMA) guidelines prepared in 2010 on ‘Management of Urban Flooding’, there should one automatic rain gauges (ARG) for every 4 sq km. The Chennai core area, which is about 176 sq km, requires at least 44 ARGs.
The guidelines document clearly emphasises the need for for having more ARGs. “Lack of spatial and temporal rainfall data over urban areas on a real-time basis is a very critical gap. Therefore, establishment of local networks for real-time rainfall data has to be accorded the highest priority.
“In the United Kingdom, the recommended rain gauge density for urban areas is 1 ARG per 4 sq km while in Malaysia, it is 1 ARG per sq km. However, the area covered by all 2325 class I, II and III cities is about 54274.59 sq km and also the total number of rain gauge stations required to cover all these cities/towns on the basis of 1 per 4 sq km will be about 13569,” the document reads.
In 2010-2012, the Indian Meteorological Department (IMD) was in the process of establishing 1,350 ARGs, 675 AWSs and 12 DWRs. However, there is no clarity on how many of these stations were set up.
S Ramakrishnan, director, Institute of Remote Sensing (IRS), which is part of the Union government’s initiative to prepare a flood atlas for Chennai, told the Express that ideally every Greater Chennai Corporation ward should have an ARG.
Chennai’s current network
North: Ennore, Madhavaram, Avadi, Redhills, Thiruvallur, Poonamalle
Central Chennai: DGP Office and Nungambakkam
South: Guindy, Anna University, Taramani, Satyabama University, Hindustan University, Meenambakkam, Kollapakkam, Kattupakkam and Chembrambakkam