Study on agro-climatic parameters in Bangladesh

Abstract

Last few years Bangladesh achieved commendable success in food production. About 80% population of Bangladesh leaves on agriculture. But the agricultural production depends on climatic conditions. In some seasons cultivation is hampered due to the shortage of water and on the other hand flood causes great damage to crops in other season. So water balance study is very necessary for cultivation. Furthermore, water balance study is also important for planners who can decide on which months irrigation is required and on which months it is not necessary for highest benefit as rainfall is not uniform all the year round. The planners may also suggest about frequency of irrigation required during different months. Climatic parameters like rainfall, temperature, wind speed, sunshine hours, relative humidity, evaporations etc. arc some of the important factors for agricultural production. Of all these rainfall data have been collected from Bangladesh Water Development Board (BWDB) and other data have been collected from Bangladesh Meteorological Department (BMD) for the year 1960 to 1996. The study area selected is all over the Bangladesh. In this project report the FAO Penman-Monteith method (1998) has been used for calcu lating the reference crop evapotranspiration from mcteorological data. The FAO Penman-Monteith method (1998) overcomes the shortcomings of the prcvious FAO Penman method and providcs values that are more consistent with actual crop water use data worldwide. The monthly average values of rainfall have been calculated for about 295 stations 111 Bangladesh for the period of 1961-1996. The monthly average values of other climatic parameters, such as maximum and minimum temperatures, relativc humidity, hours of bright sunshine, wind speed have been also calculated for 31 stations within thc country for the period of 1961-1996. The water balance study has been done at 30 stations. Water deficit and water surplus, mcan monthly rainfall, mean monthly evaporation, refcrence crop evapotranspiration and rainfall, mean monthly maximum and minimum temperature, relativc humidity and hours of bright sunshine have bccn presented cartographically. Isohyets have been drawn for mean annual rainfall andmcan seasonal rainfall. Histograms have been prepared for the monthly rainfall fi"om over 295 stations. Tabulated data are also offered to support these histograms. The mean annual rainfall ranges from 1400mm in Rajshahi region to over 5000mm in Sylhet region. In Chittagong region annual rainfall is about 3000mm. Rainfall gradient is gradual from east to west. The northeastern part of the country, that is the Sylhet region has less than 100mm rainfall for 4 months in a year. On the other hand the western Rajshahi and western part of Nawabganj district have less than IOOmm rainfall for 7 to 8 months. Northeastern part of the country has aridity indcx more than one for 7 months, at southern part it is 6 months but at western part has aridity index more than one only for 4 months. At eastern part of the country water surplus starts form the month of April and at the west water surplus starts from the month of June. These observations show that the results are very much consistent with the geographical location (which determines the occurrence of rainfall) of different parts of Bangladesh.