Climate Change and Sustainable Irrigation Management for High Value Crops in Bangladesh by Md. Shirazul Islam and Md. Harun-ur-Rashid
Predictions World Watch Institute (2007) Bangladesh is under serious risk from sea level rise due to climate change Ahmed and Roy (2007) Climate change will disrupt significantly the agro-environmental practices and socioeconomic activities of the country
Predictions (continued) Koudstaal and others (1999) Salinization in the dry season and prolonged inundation in the wet season Hassan and Hoque (2008) Flood area will increase by about 6% resulting in crop production loss of about 11% in the Ganges basin, 7% in Meghna basin and 2% in Brahmaputra basin
Selvaraju (2006) Increase winter temperature affecting wheat and pulse cultivation, increase spikelet sterility and reduce crop yield
Irrigation & Water Management Scenario in Bangladesh
Summary of irrigation equipment and area coverage Equipment Number in operation Area coverage (ha) % of total irrigated area DTW 27,117 6,54189 13.67 STW 11,28,991 31,59,899 66.00 LLP 99,255 8,38,377 17.51 Gravity flow - 1,09,381 2.29 method Traditional method - 25,500 0.53 Source: Minor irrigation survey report 2004-2005, MoA, Bangladesh
Groundwater irrigation About 75% groundwater irrigation About 74300 Mm 3 of groundwater is needed annually for irrigation
Groundwater irrigation (continued) Water table declination is observed in many irrigated areas of the country This has restricted the use of suction mode pumps in the areas
Water distribution systems Mostly unlined channels A few buried pipe water distribution systems Some lined channels High water loss in distribution systems Low system efficiency (Rice: average 30-35%; Other crops: 40-60%)
Losses in distribution systems Distribution system Water loss (l/s/100 m) Buried pipe (BP) 0.35-0.53 Lined channel system 1.52-2.10 Unlined channel system 4.1-10.32 Flexible (hose) pipe 1.15-1.50
Tubewell utilization No regulation on irrigation appliances since 1992 Density of installation of shallow tubewells increased Irrigated area of <0.5 ha under a 14 l/s capacity STW
Tubewell utilization (continued) Tube wells installed in light textured soils, irrigate almost every day causing huge seepage and percolation losses
Effect of Climate Change on Soil, Water and Crop Production
Effect on Soil Characteristics Potential changes in soil organic matter supply from biomass, soil temp. and soil hydrology Other changes due to change in temperature and precipitation are expected to be relatively well buffered by the mineral composition, the organic matter content or the structural stability of many soils
Effect on water productivity Water productivity will be limited by the amount of water available Due to erratic climatic conditions, more area are expected to come under water restrictions giving rise to low water productivity
Water productivity of some crops Crop Water productivity (Kg/ha-mm) Rice 5-6 Wheat 12-15 Maize 15-18 Potato 35-40 Tomato 100-115 Brinjal 55-65 Onion 25-30
Effect on Crop Production Shallow rooted plants will suffer most With the rise of temperature, plants will require more water for evapotranspiration Unless the cropwater demand is met, yield will decrease
Effect on Crop Production (continued) Some crops will be eliminated or produce less yields Increased insect infestation and pest and disease infections to crops will appear as a great problem
Effect on Soil Salinity Bangladesh has, at present, about 1.0 mha of lands under various levels of salinities which is expected to increase further and extend towards inland
Category of soil salinity and saline areas Category of salinity (ds/m) Mapping S Unit 1 S 2 S 3 S 4 S 5 2-4 4.1-8 8.1-12 12.1-16 >16.0 1 82260 31590 1520 - - 2 170380 110390 29420 - - 3 35490 113890 61240 25870 2650 4 1630 36060 73400 55130 32750 5-15270 25900 64100 51740 Total 289760 307200 191550 145100 87140 Source: SRDI (2000)
Effect on Drought Every year, 3-4 million hectares of land are affected by droughts of different magnitudes Stress resulting from higher crop ET and reduced rainfall may override any growth benefits from the higher CO 2 levels, unless irrigation can be stepped up to compensate the deficit soil moisture
Effect on Drought (continued) Aman rice is grown rain fed in about 60% of cultivable land (8.3 Mha) The crop suffers from drought of different intensities A heavy loss to Aman production affects the economy of the farmers
Drought Intensity and yield loss of T. Aman Intensity of drought Land area, hectare Yield loss due to drought,% Very severe 342990 70-90 Severe 737028 50-70 Moderate 3154950 30-50 Slight 2867895 10-30
Effect on Floods Climate change will cause greater intensity floods damaging more crops, lives and other properties Flash floods will also be frequent and dangerous for some areas of the country
Effect on Floods (continued) In 2002, flash floods damaged shelters and crops of about 31,500 hectares in 12 upazillas of Chittagong and Cox s Bazar districts In 2007, flood hit twice a year damaging the crops, human and cattle lives and shelters, and other properties
Effect on Cyclones and Tornadoes Climate change will enhance frequent cyclones and tornadoes of high intensities This will threaten Bangladesh agriculture most
Possible Measures for Sustainable Water Use in Crop Fields
Optimization of Water Use Already the drying and wetting method of water application has been proved to be very useful to save 50% water without any or a little sacrifice of rice yield
Use of drip irrigation method High value crops like tomato, egg-plant, potato, papaya, watermelon etc. can be irrigated For saline soils, this method can be a good choice for the coastal farmers
Controlled Application of water Fertigation
Crop production in saline soils Methods used Drip, raised bed and mulch Traditiona l method Location: Noakhali Crop Yield, Salinity, t/ha t/ha Tomato 50-70 10-12 (4.5-5.5) Watermelon Tomato Watermelon 40-50 18-20 15-18 10-12 (4.5-5.5) 10-12 10-12 Location: Satkhira Crop Yield, Salinity, t/ha ds/m Tomato 48-55 9-10 (4.75-6.15) Okra Tomato Okra 10-11 16-19 5-6 N.B. Figures in parenthesis indicate reduced soil salinity due to improved management practices 9-10 (4.75-6.15) 9-10 9-10
Improved distribution system Channel compaction has been found to increase command area by about 10-30% Proper use of a good quality hose pipe can save 95% water loss
Improved distribution system (continued) Buried pipe water distribution system (BPS) It can take care of land undulation, land loss (1.8-2%), irrigation cost and water distribution uniformity
Change in cropping pattern 1. A change in cropping pattern in these areas with non-rice crops can make irrigation much more profitable 2. Low water requiring crops like wheat, maize, potato and horticultural crops can be grown for more benefits
Annual water requirements of different crops Name of crop Area cultivated, 000 ha Seasonal crop water requirement, mm Approx. Irrig. water requirement, Mm 3 Rabi season (October-February) Boro rice 4675 650 759688 Wheat 370 300 2018 Potato 400 280 2036 Maize (w) * 346 450 2831 Mustard 547 200 1990 Groundnut 70 250 318 Vegetables(w) * 448 250 2034 Onion 158 230 659 Garlic 64 230 266 Sub-total 88121 N.B: (w) * = winter; ** = Supplemental irrigation
Annual water requirements of different crops (continued) Name of crop Area cultivated, 000 ha Seasonal crop water requirement, mm Approx. Irrig. water requirement, Mm 3 Kharif-I season (March-May) T.Aus** 1154 240 6924 Vegetables** 231 120 504 Maize** 30 100 55 Sub-total 7483 Kharif-II season (June-September) Aman rice** 1154 120 3461 Sub-total 3461 Grand Total: 99065 Mm 3 N.B: (w) * = winter; ** = Supplemental irrigation
Construction of water management infrastructures The constructed structures provide flood protection to about 3.5 million ha of land In the coastal areas over 12 million people are receiving the benefits of around 3,600 km embankment
Maintaining well spacing regulation
Conjunctive use of water Conjunctive use of surface and ground water for sustainable irrigation management Government has also emphasized on surface water utilization to reduce pressure on groundwater
Upgrading Farmers Knowledge Most of the farmers of the country are illiterate and do not have much idea about consequence of the misuse of irrigation water They should be made aware of the water managements in irrigated agriculture through trainings, demonstrations and group discussions
Conclusions Water conveyance systems should be improved Irrigation of diversified crops, especially the high value crops, should be encouraged Farmers should be made aware of water losses and the ultimate effects Conjunctive use of water for irrigation should be encouraged
conclusions (continued) Government should take necessary measures to install Buried Pipe Water Distribution Systems by phases all over the country Existing rules of tubewell installations should be revived Mass media should be used to propagate the water management messages to general people