Flood forecast and monitoring is essential part of Central Water Commission’s (CWC) work. Presently, the agency claims[I] issuing flood forecasts at 332 sites including 133 Inflow Forecast (IF) sites and 199 Level Forecast (LF) sites. Since 2018, SANDRP has been presenting critical analysis of CWC’s flood forecast website[II] in region wise manner.
In 2022 SW monsoon season, we have already published the overviews for North[III] and North East[IV] regions of the country. This third part in the series covers the states in East India including Bihar, Jharkhand, Chhattisgarh, Odisha and West Bengal (Ganga Basin). Our previous overviews for the region can be seen here (2018[V]) and here (2019[VI]).
(Feature Image: Pillar with flood level marked on the bank of Yamuna river at Old Railway Bridge level forecast site in Delhi. Source:- Sanchit Khanna/HT Photos)
During monsoon season, Centre Water Commission’s (CWC) carries flood monitoring and forecast work through a network of 332 stations[i] covering 20 major river basins. The stations are comprised of Level Forecast (LF), Level Monitoring (LM) and Inflow Forecast (IF) sites. The LF sites have Warning Level (WL), Danger Level (DL), Highest Flood Level (HFL), date of HFL information while LM sites maintain HFL and HFL date records. At IF sites flood level for respective dams/ barrages with inflow, out flow figures are measured and forecast is issued accordingly.
However, there are plenty of concerns plaguing CWC’s flood forecast and monitoring work across country for years. In this 2022 SW monsoon season, the agency has exhibited one more problematic tendency which exhibits not only its careless approach vis-a-vis keeping accurate information of HFL breach events, but it also seems strange that it realises it has giving wrong HFL level and date information mostly only after crossing the HFL now.
During monsoon CWC (Central Water Commission) monitors water level at several hundred sites in the county and publishes this information on its Flood Forecast website[I]. The website has three ways to get this information: Data Flow Map, List Based Exploration, and Hydrograph view. The Hydrograph view provides information for past 72 hours, supposed to be updated every hour. This is in addition to the list of current forecasts listed on the website.
Since 2018, SANDRP has been analyzing CWC’s flood forecast website in zone wise manner. After examining status of flood forecast and monitoring sites in North Indian[II] states, this overview is for North East India region covering Arunachal Pradesh, Assam, Meghalaya, Manipur, Nagaland, Tripura, Mizoram and Sikkim states. This also includes part of North West Bengal that is in Brahmaputra basin. Our 2018 and 2019 analysis on the North East region can be seen here[III] and here[IV]. .
In the monsoon season of 2019 Indian rivers have crossed Highest Flood Level (HFL) at around 37 Level Forecasting and Level Monitoring sites across the country. This account attempts basin wise details and description of HFL breached by the rivers.
Brahmaputra Basin (Assam)
In Brahmaputra basin 2 sites, 1 Aie NH Xing Level Monitoring site on River Aie in Barpeta district of Assam and Dhubri (Level Forecast) site on River Brahmaputra in Dhubri district of Assam narrowly crossed the HFL in July 2019.
Also River Barak at ANIPUR site in Karimganj district on May 24 and River Brahmaputra at Goalpara site in Goalpara district rose close to the HFL level on July 17, 2019. As per CWC (Central Water Commission) FF Website, Goalpara site has not crossed HFL since 1954.
The release of around 1.31 lakh cusecs of water in Yamuna from Hathnikund barrage at 09:00 hours on July 26, 2018, was certainly first surge of flood this monsoon in the river. But no one expected, most are still in the dark that the release would multiply by over five times in just two days! It is almost a month after the Southwest monsoon arrived. By this time the river usually floods couples of times.
Looking at the lack of significant rainfall in the catchment area over past weeks, the flood is unexpected and has taken many by surprise. The Irrigation and Flood Control Department, Delhi Government has issued warning for flood plain farmers and human settlements close to river banks, but the warning does not seem to commensurate with the flood peak that is likely to hit the capital in next day or two.
Yamuna has already crossed warning (204 m) and danger level (204.83) at Old Delhi Railway Bridge (ORB), Delhi. The High Flood Level is 207.49 meters, reached on Sept 6,1978 after around 7 lakh cusecs (cubic feet per second) water was released in Yamuna on 3rd Sept 1978 at 04:00 hrs from Tajewala barrage, that was decommissioned and replaced by Hathnikund barrage in early 1990s. The flood monitoring of River Yamuna began in 1963.
Since then, the river has seen high floods in 1988, 1995, 2010 and 2013. The 2010 and 2013 floods also crossed 207 metres mark but fell short of 1978 level.