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Impacts of Climate Change on Actual Evapotranspiration of Boro Rice in North-east Hydrological Region of Bangladesh

MD. ABEDUR RAHMAN
MASTER OF SCIENCE (AGRICULTURAL ENGINEERING)IN IRRIGATION AND WATER MANAGEMENT, DEPARTMENT OF IRRIGATION AND WATER MANAGEMENT, BANGLADESH AGRICULTURAL UNIVERSITY, MYMENSINGH-2202 Examination Roll No. 13 IWM JJ 01 M Registration No.35598,Session: 2008-2009 Semester: January-June 2014

Abstract/ Executive Summary:

Climate change is one of the most important global environmental challenges facing humanity with implications for food production, natural ecosystem and water supply. Climatic anomalies will play an important role in increasing the uncertainties in crop production. A changing climate is likely to bring changing patterns of climate variability. While change in long-term mean climate will have significance for global food production and may require ongoing adaptation, greater risks to food security may be posed by changes in year-to-year variability and extreme weather events. This study was undertaken to assess the impacts of climate change on actual evapotranspiration (ETc) of boro rice in Srimongal upazila of Maulbibazar district and Sylhet district in the North-East Hydrological Region of Bangladesh. Two popular varieties of boro rice, BRRl dhan28 and BRRI dhan29, which covered 45.59% and 48.53% of the area, were selected for this study. Climatic data like daily maximum and minimum temperatures, maximum and minimum relative humidity, wind speed and sunshine duration were collected for a period of 17 years (1994-2010) from the Bangladesh Meteorological Department. The determination of reference crop evapotranspiration (ETo) was determined by employing the FAO Periman-Monteith method. By multiplying ETo by a crop coefficient (Ke) actual evapotranspiration of the two rice varieties at different growth stages was determined. The trend of ETc was detected and estimated by MAKESENS trend model. The results revealed that crop coefficients of rice at different growth stages vary with changing relative humidity in different years and with changing wind speed in different sowing times. Due to the variation of K; and ETo, the ETc varied at different growth stages and also over the total growing season. The water demand of BRRI dhan28 varied from 450.23 to 588.47 mm and 444.72 to 523.54 mm in Srimongal upazila and Sylhet district, respectively. For BRRl dhan29, the corresponding variations in water demand were from 511.31 to 666.65 mm and 520.41 to 601.9 mm. There was a decreasing trend of water demand of the two rice varieties in Srimongal but an increasing trend in Sylhet district due to the effect of climate change. For irrigation management of boro rice cultivation in Srimongal upazila and Sylhet district, the predicted results would be useful. The results will make it possible to optimize utilization of valuable water resources and will help sustaining agricultural production to contribute in the food security of the country.

Keywords: Impact, Climate change, Actual ET, Boro-rice, North-east region

Location: Srimongal upazila of Maulbibazar district and Sylhet district in the North-East Hydrological Region of Bangladesh

Start Date: 00-01-1994

End Date: 00-12-2010

Program Area: Risk Management in Agriculture

Non-commodity: Adoption and mitigation technology

Objectives:

1.To determine actual evapotranspiration of two boro nee varieties at different growth stages, 2. To detect and estimate long-term trends of actual evapotranspiration of the boro rice varieties, and 3. To evaluate the impact of climate change on actual evapotranspiration of the boro rice varieties.

Methodology:

The North-East hydrological region was selected for this study. There are four districts in NE hydrological region, but only Sylhet sadar and Srimongal upazila of Maulbibazar district have weather stations. Consequently, this study was based on the data of these districts. The Northeast Region has a typical tropical monsoon climate characterized by the twice- yearly reversal of air movement over the region. For four months in winter (December through March) air flows to the region from northeast, while for four months in summer (June through September) it flows to the region from the southwest. These airflows or winds are called monsoons; that of winter called the northeast monsoon while that of summer is called the southwest monsoon. A reversal of the monsoons takes about two months, the first occurring in spring (April-May) when the change of wind direction is from northeast to southwest via northwest, and the second occurring in autumn (October-November) when the change is from southwest to northeast VIa southeast. These periods of changing wind direction are called the spring and autumn reversals. Across the Northeast Region, rainfall during the southwest monsoon ranges from around 1500 mm in the southwest to around 4100 mm in the northeast at the border with Meghalaya. The northeast monsoon brings dry air into the region from China, and rainfall in this season ranges from around 80 mm in the southwest to around 220 mm in the northeast. The spring reversal is characterized by increasing rainfall ranging from around 490 mm in the southwest to around 1290 mm in the northeast. The autumn reversal is characterized by decreasing sporadic rainfall ranging from around 170 mm in the southwest to around 320 mm in the northeast. Daily agro-climatic data like rainfall, maximum and minimum temperatures, maximum and minimum relative humidities, wind speed and sunshine duration of Sylhet district and Srirnongal upazila of Maulbibazar district for a period of 17 years (1994-2010) were collected from the Bangladesh Meteorological Department. Data was analyzed FAO Penman-Monteith equation.

Source of Information: MASTER OF SCIENCE (AGRICULTURAL ENGINEERING)IN IRRIGATION AND WATER MANAGEMENT, DEPARTMENT OF IRRIGATION AND WATER MANAGEMENT, BANGLADESH AGRICULTURAL UNIVERSITY, MYMENSINGH-2202 Examination Roll No. 13 IWM JJ 01 M Registration No.35598,Session: 2008-2009 Semester: January-June 2014

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

1. Due to changes of relative humidity and wind speed, adjusted crop coefficients of BRRI dhan28 and BRRI dhan29 at different growth stages in different years and sowing times varied. 2.Crop-water demand/actual crop evapotranspiration at different growth stages and in total growing season varied due to variation of crop coefficient, Kc, and reference crop evapotranspiration, ETo• These variations occurred due to the variation of climate, length of growth stages, seeding time and length of total growing season. 3. The water demand of BRRI dhan28 for first seed sowing varied from 450.23 to 588.47 rom and 444.72 to 523.54 rom in Srimongal upazila of Maulbibazar district and Sylhet district, respectively. For BRRI dhan29, the corresponding variations were from 511.31 to 666.65 mm and 520.41 to 601.9 mm for first seed sowing. 4. There was a decreasing trend of water demand of the two rice varieties in Srimongal and increasing trend in Sylhet district due to the effect of climate change. 5.For irrigation management of boro rice cultivation in Srimongal upazila of Moulovibazar district and Sylhet district, the predicted results would be useful.

Knowledge Management: Thesis