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Temperature, Precipitation and Net Irrigation Requirement Scenario for Major Winter Crops in the South-eastern Bangladesh

Molla Karimul Islam
Institute of Botany and Landscape Ecology, University of Greifswald, German

Shaibur Rahman Molla
Dept. of Environmental Science and Technology, Jessore University of Science and Technology (JUST), Jessore-7408, Bangladesh

Mohammad Mahfuzur Rahman
Dept. of Environmental Science and Technology, Jessore University of Science and Technology (JUST), Jessore-7408, Bangladesh

Kushal Roy
Environmental Science Discipline, Khulna University, Khulna-9208, Bangladesh

Abstract/ Executive Summary:

Bangladesh ranked top among the climate vulnerable countries in the world. Climate change is evident since few decades. Changing climate affects the life, property and economy of the country. Among them, agricultural is the most affected sector. Literature suggests that the future climatic condition might affect the agriculture even more adversely. Therefore, considering the economic strength, agriculture based economy and population density, the country needs much effort to adjust with the changing circumstances. A clear and specific understanding of the apprehending changes would certainly assist in preparation to fight against the adverse impact. Aiming to provide updated knowledge about the climate change scenario and future irrigation water demand, this study simulated the temperature, precipitation and net irrigation requirement (NIR) scenario for Boro, Potato and Wheat crop for the south-eastern part of Bangladesh. MAGICC/SCENGENE model was used to simulate local scale temperature and precipitation scenario considering Special Report on Emission and Radiation (SRES) A1B-AIM emission scenario and thereafter simulated NIR based on the temperature and precipitation scenario using the AquqCropmodel. The MAGICC/SCENGEN model was calibrated and validated using the observed datasets collected from 12 weather stations of Bangladesh Meteorological Station (BMD). The changes in temperature, precipitation and NIR are estimated based on the11 year mean values extending from the year 2000 to 2010 (as the base data). The analysis reveals that the south-eastern part of Bangladesh is likely to experience diverse trends of climatic change. The temperature showed a linear trend of increment ranging from 1.4°C to 2.4°C by the year 2100. The changes would not be the same for all season. Winter temperature showed maximum changes as compared to that of base period. On the other hand, the changes in precipitation showed two trends. Precipitation scenarios showed initial increase until 2040 and thereafter decline in 2050. After 2050 the total precipitation is likely continue to increase. However, it showed substantial variability throughout the seasons. The area would receive less rainfall during pre-monsoon, while the precipitation is likely to increase in the post-monsoon. NIR scenario suggests a steady increase for all three winter crops. The NIR might be increased by 10 to 25% depending on the crop types. AquaCrop model estimates the irrigation water requirement based only on soil moisture stress level and carbon-di-oxide (CO2) fertilization.It does not include organic matter depletion, initial moisture stress, impact of salinity etc. Despite this simplicity, the study outcome provides important implications for the policy practitioners to ensure future food security and water management challenges.

Keywords: Climate change, Net irrigation requirement, MAGICC-SCENGEN, AquaCrop Model, South-East Bangladesh

Location: Chittagong, Cox's bazar, Rangamati, Bandarban, Khagrachhari, Feni, Lakshmipur, Comilla, Noakhali, Brahmanbaria and Chandpur

Start Date:

End Date:

Program Area: Crop-Soil-Water Management

Commodity: Water management

Objectives:

This study also estimates the changes in irrigation water requirement for three main rabi crops for the south-eastern parts of Bangladesh under SRES (Special Report on Emission Scenarios)A1B-AIM climate scenarios (see IPCC, 2001 for more details about SRES A1B-AIM emission scenarios).

Methodology:

Study area: This study analyzes the climate change impacts on net irrigation requirement for three major crops in the south-east region of Bangladesh. The study area is about 34418.44 km²and covers nearly 25 percentage of the total land area of Bangladesh. The study area encompasses 11 administrative districts (Chittagong, Cox's bazar, Rangamati, Bandarban, Khagrachhari, Feni, Lakshmipur, Comilla, Noakhali, Brahmanbaria and Chandpur) of Bangladesh. The area is inhabited by over 27 million people with a density of 795 person/km². (Bangladesh National Portal; http://www.bangladesh.gov.bd/; accessed on July 4, 2016). Study area receives about 3028 mm of precipitation annually and experiences three distinct seasons (pre-monsoon, monsoon and winter (BMD, 2012). The pre-monsoon season (March-May) is characterizes with hot summer and sporadic rains and hails. The monsoon season extends from June to October associated with 80% of the total annual rainfall. The winter season (December-February) usually offers the best growing season with relatively low temperature, little rain and extended cultivable land. Since winter season receives little or no rain, it demands irrigation for agriculture. The irrigation within the study area mainly comes from surface and ground water sources. Data: Analysis was done based on 64 year (1948-2011) meteorological data collected from 12 weather stations of Bangladesh Meteorological Department (BMD) located within the study area. Station-wise monthly mean temperature, rainfall, relative humidity, sunshine hour and wind speed data were collected from BMD. Generation of future climate scenario: To generate the future climate scenario for the study area, a reputed regional climate scenario generator software package namely MAGICC/SCENGEN (Model for the Assessment of Greenhouse-gas Induced Climate Change a regional climate SCENnario GENerator) version 5.3.v2 was used (MAGICC and SCENGEN, 2000). MAGICC/SCENGEN is user friendly interactive software suites that allow users to examine future climate change and its uncertainties at both the global-mean and regional levels based on the scenarios of General Circulation Models (GCM). MAGICC calculations consider the same global mean value that has been employed by Intergovernmental Panel on Climate Change (IPCC). SCENGEN uses MAGICC results, together with spatially detailed results from the CMIP3/AR4 archive of Atmosphere-Ocean Global Circulation Models (AOGCM), to produce spatially detailed information on future changes in temperature, precipitation and MSLP, changes in their variability, and a range of other statistics. MAGICC/SCENGEN has been one of the primary tools used by IPCC since 1990. The detail working principle of MAGICC/SCENGEN can be found at Wigley (2008). The spatial resolution of MAGICC/SCENGEN is 2.5⁰ and whole Bangladesh is covered by only six pixels. This study analyzed only one pixel that covers the south-eastern part of the country. The analysis assumes a uniform change of climate over the whole study area. The scenario generation for the study area using MAGICC/SCENGEN comprises two main steps. In the first step, MAGICC model was run to generate ensemble scenarios. This involves choosing a pair of emission scenarios, termed as the Reference and Policy scenario. This study considers SRES A1B-AIM emission scenario (balance across all sources). Default options for carbon cycle, carbon cycle climatic feedbacks, aerosol forcing, climate sensitivity, thermohaline circulation, vertical diffusivity and ice melt were opted for this study. In the second step, options were chosen to acquire the actual projections for the selected climate variable, the set of GCMs to be averaged and the future date of interest to run SCENGEN. Modeling net irrigation requirement: To model future net irrigation requirement under climate scenarios generated by MAGICC/SCENGEN a separate model as suggested and developed by Food and Agricultural Organization (FAO) namely AquaCrop (version 3.1 Plus) was used. The ET0 calculator (Raes et al., 2009) uses Penman-Monteith equation for calculation of evapotranspiration. The inputs for the calculator are maximum air temperature, minimum air temperature, relative humidity, sunshine hours and wind speed at a height of 2 m. In this study, the inputs for ET0 calculator was determined based on the 11 year long (1990-2000) average apart from maximum and minimum air temperature. ET0was calculated for each of the projected climatic scenario of 2025, 2050 and 2075. Other options chosen for AquaCrop model.

Source of Information: J. Sci. Technol. Environ. Inform. 03(02): 220-230| Islam et al. (2016)

Article Link (Online Journal): DOI: http://dx.doi.org/10.18801/jstei.030216.25

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Bangladesh is considered as the most vulnerable country of the world to climate change impacts due to a number of hydro-geological and socio-economic factors. The international community also recognizes that Bangladesh ranks high in the list of most vulnerable countries on earth for climate change impacts. The South-East region of Bangladesh has already faced the worst look of climate change impacts. The increasing temperature, erratic precipitation and other natural disaster are seen in this region of at a high magnitude and increasing frequency. This research practices can help us with additional information for adopting better options to face the problem of apprehending climate change.This modeling effort was done with a view to projecting the future climate scenario and to find out the climate change impact on crop production in the south east region of Bangladesh using the MAGICC/SCENGENE-Aqua Cropmodel.The research outcome suggests that this region would face the increase of temperature and rainfall variability. Increasing temperature and variable rainfall would affect the future crop production. Although it can be argued that the increasing trends of atmospheric carbon-di-oxide (CO2) could afford to increase in production, simultaneously, it is likely to require higher amount of irrigation water due to the increase of temperature and subsequent evapotranspiration. Irrigation intensive crops like Boro, Potato and Wheat would be affected severely because of increasing temperature and uncertain precipitation in winter. Diminishing rainfall in winter and erratic rainfall variability over time and space would consequently, increase the severity of moisture stress which in turn will lead to drought conditions. The net irrigation water requirement for the irrigation feed crops will increase for the future years.It is to note that, AquaCrop model estimates the irrigation water requirement based only on soil moisture stress level and carbon-di-oxide (CO2) fertilization. It does not include organic matter depletion, initial moisture stress, impact of salinity etc. Despite this simplicity, the study outcome provides important implications for the policy makers to ensure future food security and water management challenges.

Knowledge Management: Journal