By Sharad Chandra, Commissioner (Flood Management) and Rajesh Kumar, Sr. Joint Commissioner (Flood Management), Department of Water Resources, River Development & Ganga Rejuvenation, Ministry of Jal Shakti, New Delhi, India

Introduction

Disastrous floods of 1954 necessitated a paradigm shift from using only structural measures for flood control to the starting of non-structural measures for mitigating floods. One of the important recommendations of the “High Level Committee on Floods” constituted by the Government of India in April 1957 was “Absolute or permanent immunity from flood damage is not physically attainable by known methods of flood control. Flood Plain Zoning and Flood Forecasting & Warning and like measures should therefore be given due importance, particularly, as they don’t require large capital investments”.

Flood Forecasting & warning service as the most important, reliable and cost-effective non-structural measures for flood mitigation, was initiated by erstwhile Central Water & Power Commission in India in November 1958 by setting one forecasting station at Old Delhi Railway Bridge, for the national capital, on the river Yamuna.

Floods of 1968 in many parts of the country causing considerable loss of life hastened the process of flood forecasting. In 1969, Central Water Commission (CWC) was charged with the responsibility of issuing flood forecasting services in flood-prone basins of Ganga, Brahmaputra, Narmada, Teesta, Mahanadi and Coastal rivers of Orissa.

Recommendations made by 5^th Conference of State Minister’s of Irrigation and Power held at Ooty in September 1970, mention for “Extension of flood forecasting activities to other flood prone rivers; Modernisation of flood forecasting techniques; importance of meteorological organisation for assisting in flood forecasting by establishing Flood Meteorological Offices (FMO) at various flood forecasting centres under India Meteorological Department (IMD)”

In 1974, the flood forecasting activity was extended to Godavari and in 1978 to Krishna River systems. After the disastrous floods of 2001, the activity was extended to Pennar basin in South India. At the end of XI Plan, CWC had 175 flood forecasting stations in different basins of the country.

State Governments were also requested to identify the locations for expanding the network of Flood Forecasting Stations. Presently, the total number of flood forecasting stations are 340, consisting of 200 Level and 140 Inflow Forecast Stations and covering all major flood-prone river basins and States.

The CWC’s comprehensive strategy effectively aligns with the WMO’s guidelines by focusing on the timely delivery of useful information, engaging stakeholders, regularly evaluating its network and embracing technological advancements. This approach not only enhances the CWC’s flood forecasting capabilities but also significantly contributes to better flood management and community resilience in India.

Modernisation in Data Collection and Transmission

Initially, CWC was using manual gauges for observation of rainfall and water level and High Frequency (HF) Wireless Sets for data communication from remote sites to divisional flood control rooms. During 1980s, for the first time 14 stations under Upper Yamuna Basin was converted to automatic sensor-based observation of water level and rainfall and transmission through Very High Frequency (VHF) communication towers to communicate the data automatically from a remote site to the control room in the Upper Yamuna Division, CWC, New Delhi. The first satellite-based system of communication with automated data acquisition started under the Dam Safety Assurance and Rehabilitation Project (DSARP) in 1999, when 35 stations in Mahanadi Basin and 20 stations under Chambal Basin were taken up for modernisation. Two Earth Receiving Stations were also established, one at Burla (Odisha) and the other at Jaipur (Rajasthan). CWC has presently 1121 Real Time Data Acquisition System (RTDAS) stations and 29 modelling centres in various river basins.

Modernisation in Flood Forecast formulation

Conventional flood forecasting models utilises Statistical correlation and regression equations to formulate flood forecast. During 1980s, the concept of mathematical models was introduced. Currently, CWC is issuing 7-day advisories for floods at all 340 flood forecasting stations utilising MIKE-11 modelling tools. This is in addition to short-range forecast (response time upto one day) being issued by CWC utilising a statistical model.

CWC is also working on a spatial flood warning system (Flood Inundation). Spatial flood warning system for Mahanadi, Godavari and Tapi has been developed and is ready for launch.

Modernisation of Meteorological Inputs

After the recommendation made by 5^th Conference of State Ministers of Irrigation and Power held at Ooty in September 1970, IMD started FMOs in various locations to cater to the needs of Flood Forecasting. These FMOs provide Quantitative Precipitation Forecasts (QPF) to the concerned Flood Forecasting Divisions. Numerical Weather Prediction (NWP) model outputs are utilised for 7-day advisories by CWC. There are currently 15 FMOs established by IMD to provide QPF for over 160 river catchments.

Modernisation of Forecast Dissemination

Dissemination of flood forecast to the concerned first responders, who will in turn warn the general populace regarding the impending floods, started through wireless. With the advent of internet, e-mail is used for quick and reliable dissemination. Now, dedicated website for different products is available namely, http://ffs/india-water.gov.in/ for short range forecasts and http://aff/india-water.gov.in/ for 7-day advisories. These utilises Water Information Management System (WIMS) for a better data entry system, report generation and user-friendly web functions. ‘Flood Watch India’ mobile application is also available for flood-related information anytime and anywhere. CWC flood forecasting services are also integrated with ‘Sachet- Common Alerting Protocol (CAP)’ and National Disaster Emergency Management (NDEM). Various social media platforms are also being used for dissemination of flood-related information.

Disclaimer: The views expressed in this piece are those of the author/s and do not necessarily reflect the views or policies of AIDMI.