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Study of Climate Variability and Its Impact on Rice Yield in Bangladesh.

Dewan Abdul Quadir
SAARC Meteorological Research Centre (SMRC), Abhawa Bhaban, Agargaon, Sher-E-Bangla Nagar, Dhaka-1207, Bangladesh.

Tariq Masood Ali Khan
SAARC Meteorological Research Centre (SMRC), Abhawa Bhaban, Agargaon, Sher-E-Bangla Nagar, Dhaka-1207, Bangladesh.

MD. Akram Hossain
SAARC Meteorological Research Centre (SMRC), Abhawa Bhaban, Agargaon, Sher-E-Bangla Nagar, Dhaka-1207, Bangladesh.

Anwar Iqbal
Director
Bangladesh Agricultural Research Council, (BARC), Dhaka-1215, Bangladesh.

Abstract/ Executive Summary:

The severity of the damage in the crop production is expressed in terms of inundated area, flood depth and duration of flood. Considering the severity of problem, the rainfall variability and trends over a few stations of Bangladesh and in the upper catchments areas of the Ganges, the Brahmaputra and the Meghna (GBM) river system, have been studied. The trend analysis is formed on the Sylhet, Rangpur, Dhaka, Cherrapunji, Patna and Kathmandu precipitation data to investigate the area inundated during summer monsoon flooding. In another experiment, the rainfall of Dhaka is investigated with respect to Southern Oscillation Index (SOI) to explore the influence of EI Nino Southern Oscillation (ENSO) forcing on the rainfall over Bangladesh. The analysis is made for the flood events during the strong EI Nino (strong negative SOI) and strong La Nina (strong positive SOI) conditions as well as for the transition. The Aman rice yield anomalies of Bangladesh have also been investigated with respect to SOI and Dhaka rainfall. The fluctuations of rainfall show correspondence with SOI variability but the phase is found to be changing in the most recent decades. The floods occur in the years of La Nina or during the period of rapid transition from EI Nino to La Nina events. As a result, the higher yields of Aman rice are obtained for situations and yield reductions occur both for strong EI Nino and La Nina events, which are associated with droughts and floods respectively.

Keywords: EI Nino Southern Oscillation, Monsoon rainfall, Floods, Climate variability, Rice yield.

Location: Sylhet, Rangpur and Dhaka of Bangladesh, Patna and Cherrapunji of India, Kathmandu of Nepal.

Start Date: 01-01-2001

End Date: 30-06-2002

Program Area: Risk Management in Agriculture

Commodity: Weather/Climate

Objectives:

To understand the nature of the impact of these climate variability on rice production i.e., area and yields for Bangladesh;
To estimate the crop losses due to droughts and floods.

Methodology:

The long term monsoon rainfall data (1961-1999 or as available) of six stations in the catchment areas of the GBM system namely, Kathmandu of Nepal, Patna and Cherrapunji of India and Sylhet, Rangpur and Dhaka of Bangladesh have been analyzed to investigate the inter-annual variability and trends of rainfall (the historical flood record data were collected from Bangladesh Water Development Board). The values of SOI have been obtained from (NOAA, USA). The rice area and production statistics from 1969 to 2000 was obtained from Bangladesh Bureau of Statistics. The temporal data of rainfall for the monsoon season have been plotted for the above mentioned six stations. The linear regression analysis has been performed to find out the trends of the rainfall. The correlation analysis has been performed by using 11 years moving window to investigate the temporal variation of the nature of ENSO forcing over the rainfall of Bangladesh. It shows that there is a linear increasing trends of the yield which is in fact related to the technological factors such as, improved seeds, improved varieties of crops and better agricultural management. A functional relation of yield anomaly with the rainfall has been derived using the fourth order regression analysis.

Source of Information: SAARC JOURNAL OF AGRICULTURE, Vol. 1, 2003, ISSN 1682-8348, SAARC Agricultural Information Centre.

Article Link (Online Journal):

Funding Source:

1. Government

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The study shows that the summer monsoon rainfall over Bangladesh and the upstream GBM catchments has increasing trends during the recent decades. One of the major causes of the recent increase of the occurrences and severity of big floods over Bangladesh may be attributed to this increase of monsoon rainfall. The others may be the drainage congestion, deforestation in the upstream regions and enhanced melting of snows and ice over the mountains of Himalayas due to rapid rise of temperature. The excess rainfall causes floods and the deficit rainfall causes the droughts. Both the phenomena cause countable damage to the crops. It has been found that the rainfall variation in Bangladesh is influenced by ENSO forcing to a large extent. It has also been observed that the droughts are mostly associated with the EI Nino situations and the floods with the excess rainfall associated with La Nina. The Aman rice area, production and yield have been investigated with respect to SOI. The temporal plots of these variables show that the production and yield have been linearly increasing with time, while the area does not have any temporal trend. The trend equations for the production and yield were derived using the regression analysis. It is very clear from the analysis that the yield reductions were very high during 1988 and 1998 floods. The regression analysis of the yield anomaly shows that it follows a quadratic relationship with rainfall. This functional relationship of yield with rainfall in combination with the trend equation may be used for assessment of yield of Aman rice. It is recommended that such studies be conducted basin wise to develop more appropriate weather dependent yield equations for practical application.

Knowledge Management: Journal