62% high flood level breaches in Ganga basin: CWC's flood forecasting

The past month saw unprecedented flood situations in several states of the country including the national capital Delhi. The floods have taken a massive toll on human as well as animal lives and forced displacements, along with large-scale destruction of public-private infrastructure. The situation continues to be precarious as reports come in about the alarming water levels at several river sites in the country as reported by SANDRP (South Asia Network on Dams, Rivers and People).

Sandrp’s July analysis based on hydrographs published on the Central Water Commission’s (CWC) Flood Forecasting website revealed that the previous Highest Flood Levels (HFL) have been breached at least 34 flood monitoring sites across the country in the last month.

In this article we look at the overarching framework of flood forecasting, the various flood levels and the various concerns pertaining to the monitoring of floods in the country.

Concerns

SANDRP in its July report observed that of the total 34 HFL breach incidents last month. Further, 27 (79%) of these incidents have been witnessed in just four states Uttar Pradesh, Telangana, Himachal Pradesh, and Haryana. It is worth noting that 21 HFL (about 62%) breach incidents have occurred in the Ganga basin alone. Moreover, the Yamuna basin in itself has seen HFL breach incidents at 16 sites, with some sites breaching the old HFLs twice or thrice in a single month.

SANDRP has also raised concerns over the lack of monitoring by CWC in several extreme flood situation sites, one of them being the sites on the Beas River. The report highlights how the flood monitoring work by CWC and the state government in Punjab has no record available in the public domain revealing the data on flood levels in Ghaggar, Sutlej, Beas, and Ravi rivers which have flooded vast areas in Punjab and parts of Haryana and Rajasthan in July 2023. Similarly, the flood monitoring sites are inadequate in Rajasthan and Gujarat states which have witnessed extreme rainfall spells in July 2023.

The report also bears the fact that the CWC flood monitoring network does not include the biggest dams of North India, namely Bhakra, Pong and Ranjit Sagar, on Sutlej, Beas and Ravi rivers respectively. It also points attention towards what it calls “glaring lapses” in maintaining and updating HFL records by CWC, which were not updated despite complaints registered by SANDRP.

Flood Forecasting & Warning

Flood Forecasting & warning is the primary and non-negotiable step in flood mitigation. In India, the Central Water Commission (CWC) is responsible for monitoring flood situations in the country. During the designated flood period (1st May/1st June to 31st October/31st December), the CWC observes water levels/ discharges along the major rivers in the country and issues flood forecasts to the local administration/ project authorities/ State Governments and other Central Ministries such as Home Ministry, NDMA/ NDRF etc.

Flood Forecasting Network covers 325 stations covering 197 low-lying area/cities, along with 128 reservoirs across the country. The network is spread over twenty river systems viz. the Ganga & its tributaries, the Indus/ Jhelum, the Brahmaputra & its tributaries, the Barak, the Eastern Rivers, the Mahanadi, the Godavari, the Krishna Cauvery, East Flowing Rivers, Narmada, Tapi and the West flowing rivers. 

Flood forecasting and advance warnings enable the user agencies to decide on mitigating measures like the evacuation of people and shifting their movable property to safer locations. 

The Inflow Forecasts at 128 reservoirs are used by the dam authorities in the timely operation of reservoir gates for safe flood discharges downstream. In addition, to ensure adequate storage in the reservoirs for meeting irrigation and hydropower generation demands during the non-monsoon period. Such services are normally available during the flood period from 1st May/1st June to 31st October/31st December every year.

Classifications of Various Flood Situations

The Central Water Commission categorizes various flood situations for monitoring the floods in the country. Depending upon the severity of floods (flood magnitudes), flood situations are divided into the following four different categories - namely Normal, Above Normal, Severe and Extreme depending upon the river water level with reference to warning level, danger level, and highest flood level (HFL).

1. Normal Flood: The river is said to be in a “NORMAL FLOOD” situation at any flood forecasting site when the water level of the river is below the warning level.
2. Above Normal Flood: If the water level of the river at the flood forecasting site touches or crosses its Warning level, but remains below the Danger Level of the site then the flood situation is called the “ABOVE NORMAL” situation. Yellow colour has been assigned to this category.
3. Severe Flood: If the water level of the river at the forecasting site touches or crosses Danger Level but remains below the Highest Flood Level of the forecasting then the flood situation is called the “SEVERE FLOOD” situation. Orange colour has been assigned to this category. In “Severe Flood Situations” a special “Orange Bulletin” is issued by the Central Water Commission to the user agencies which contains the “special flood message” related to the severe flood. This is updated every three hours.
4. Extreme Flood: The flood situation is said to be “EXTREME” when the water level of the river touches or crosses the “HIGHEST FLOOD LEVEL” (HFL) recorded at any forecasting site so far. The red colour has been assigned to this category. In “Extreme Flood Situations” a special “Red Bulletin” is issued by the Central Water Commission to the user agencies which contains the “special flood message” related to the extreme flood and is updated every hour.

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