Brief note on the Predictability, Forecasting and Warning of Drought

Predictability of Drought:

As drought is very much linked with the performance of the monsoon, the predictability of drought is also linked to the monsoon. However, monsoon, by its inherent nature is highly variable^ time and space which means that rainfall is neither uniform nor evenly distributed. For good agriculture, well distributed and evenly spaced spells of monsoon rain are required. But in actual circumstances, it is rarely so.

However, the good feature is that monsoon rains arrive towards the end of May or early June even if there is a delay of few days and the monsoon never fails the entire country.

Thus, widespread drought is not a very frequent occurrence in India. This inherent characteristic of the monsoon rains (which provide about 80% of the annual rainfall in India) emphasizes that the predictability of droughts in India – either on local scale of district or a group of districts or on larger scale of a state or group of states – is achievable on a working basis of monitoring the rainfall – especially the monsoon rainfall – over the target region and taking into account the antecedent rainfall history of last one or two monsoon seasons.

Forecasting of Drought:

There is a intimate link between the performance of monsoon and the incidence of drought. Therefore, it should be obvious that forecasting of drought is almost wholly linked to the ability to forecast monsoon, i.e., to forecast its timely onset and the season’s rainfall.

It is within the capability of science to indicate broadly the date of onset of monsoon over Kerala and to give a forecast of the overall rainfall for the country as a whole during the monsoon season, which lasts from June to September. It is also possible to issue day-to-day forecasts of the progress of monsoon over different parts of the country.

Therefore, the occurrence of rain over all parts of the country is closely monitored and analyzed keeping in view the rainfall history of the previous years. Thus, it is possible to indicate the likelihood of drought over an area and to monitor its subsequent condition.

However, it has to be kept in mind that as already stated, drought does not have a sharp starting point. It builds over a period of time when apart from the availability of rains, factors such as water use and availability of additional water resources (from rivers, tube-wells) has to be taken into account.

Warning of Drought:

Of the main natural disasters, droughts are unique in terms of length of time between the first indications from, for example, rainfall monitoring that a drought is developing and the point at which it begins to impact significantly upon the population of the affected area. The requirement of the length of such “warning time” varies significantly between societies.

Early warning system indicators are:

i. Meteorological

ii. Agricultural

iii. Remote sensing

However, the Agriculture and Revenue Departments of the States remain watchful during the dry weather seasons and the situation is monitored regularly especially for those areas which are known to be drought prone due to local climatic conditions, scarcity of ground water and absence of irrigation facilities.

As drought is forecast and monitored on the basis of the availability of water (mainly through monsoon and from underground sources to some extent), meteorological forecast and warning systems and satellite monitoring of underground water sources and the condition growing crops constitute the basis of drought monitoring and warning system.