Playing catch up in flood forecasting technology
Paper:
Mains: General Studies-III: Technology, Economic Development, Bio diversity, Environment, Security and Disaster Management
Context:
India needs a technically capable workforce that can master ensemble weather and flood forecast models.
Background:
- There are many times this happens in India during flood events, when the end users (district administration, municipalities and disaster management authorities) receive such forecasts and have to act quickly.
- These compelling scenarios are often experienced across most flood forecast river points, examples— in Assam, Bihar, Karnataka, Kerala or Tamil Nadu.
- Compare this with another form of flood forecast (known as the “Ensemble forecast”) that provides a lead time of 7-10 days ahead, with probabilities assigned to different scenarios of water levels and regions of inundation.
- An example of the probabilities ahead could be something like this: chances of the water level exceeding the danger level is 80%, with likely inundation of a village nearby at 20%.
- The “Ensemble flood forecast” certainly helps local administrations with better decision-making and in being better prepared than in a deterministic flood forecast.
Ensemble forecasting model:
- The ensemble forecasting model is popular in some developed nations.
- This type of forecast provides probabilities assigned to different scenarios of water levels and regions of inundation with a lead time of around 7-10 days.
- Ensemble weather models also measure uncertainty by causing perturbations in initial conditions and hence are more exhaustive forecasts.
- The “Ensemble flood forecast” can help local administrations with better decision-making and in being better prepared than in a deterministic flood forecast.
- The IMD has begun testing and using ensemble models for weather forecast through its 6.8 peta flops supercomputers (“Pratyush” and “Mihir”).
Deterministic forecasting model:
- India currently employs the “Deterministic forecasting” model, i.e., it only provides a “Rising” or “Falling” type forecast.
- The flood forecast merely uses the words “Rising” or “Falling” above a water level at a river point and does not provide any idea of the area of inundation or its depth.
- The “lead time” or the time available to act in case of such a model is just 24 hours. So the end-users receiving such forecasts have very little time to act.
- The length of time from issuance of the forecast and occurrence of a flood event termed as “lead time” is the most crucial aspect of any flood forecast to enable risk-based decision-making and undertaking of cost-effective rescue missions by end-user agencies.
Flood forecasting system in India:
- The India Meteorological Department (IMD) issues meteorological or weather forecasts of rainfall.
- The Central Water Commission (CWC) integrates the rainfall forecast (also known as Quantitative Precipitation Forecast or QPF) into its system to issue flood forecasts at various river points.
- The CWC then disseminates this data to end-user agencies (district administration, municipalities and disaster management authorities), who take necessary precautionary measures.
Issues and Concerns:
- The shortcomings of the Indian flood forecasting system are a major point of concern.
- Impact on the flood forecasting system:
- Outdated technologies and a lack of technological parity between multiple agencies not only decrease crucial lead time but also increase the forecasting errors.
- This burden of interpretation ultimately shifts to hapless end-user agencies. The outcome is an increase in flood risk and disaster.
- Most flood forecasts at several river points across India are based on outdated statistical methods that cannot enable a lead time of less than 24 hours.
- These statistical methods also fail to capture the hydrological response of river basins between a base station and a forecast station.
- The flood forecasting system in India depends on the coordination of multiple agencies.
- Given that flood forecasting needs the CWC and IMD to complement each other’s works, it has been observed that the technological gap limits of one agency can limit the effectiveness of the other.
- The lack of technological parity between multiple agencies can have a detrimental impact on the overall effectiveness of the flood forecasting system in India.
- The lack of an adequately dense S-band radar network in India is a cause of concern. This can enlarge the forecast error in QPF which would ultimately reflect in the CWC’s flood forecast.
- These S-band Doppler weather radars with a range of 250-300 km and higher accuracy can help provide more accurate QPF.
Way forward:
- The CWC will have to work towards achieving technological parity with the IMD in order to couple ensemble forecasts to its hydrological models.
- It will have to work towards modernising its telemetry infrastructure and work towards improving its river basin-specific hydrological, hydrodynamic and inundation modelling capabilities.
- This will require a technically capable workforcethat is well versed with ensemble models and capable of coupling the same with flood forecast models.
- India should work towards probabilistic-based flood forecasts with a lead time of more than seven to 10 days and also work towards better integration between multiple flood forecasting agencies.