Climate Change and Sustainable Irrigation Management for High

Value Crops in Bangladesh

byMd. Shirazul Islam

and Md. Harun-ur-Rashid

PredictionsWorld 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 socio-economic 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

Equipment Number in operation

Area coverage (ha)

% of total irrigated area

DTW 27,117 6,54189 13.67STW 11,28,991 31,59,899 66.00LLP 99,255 8,38,377 17.51Gravity flow method

- 1,09,381 2.29

Traditional method

- 25,500 0.53

Summary of irrigation equipment and area coverage

Source: Minor irrigation survey report 2004-2005, MoA, Bangladesh

Groundwater irrigation• About 75% groundwater irrigation• About 74300 Mm3 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%)

Distribution system Water loss (l/s/100 m)Buried pipe (BP)

Lined channel systemUnlined channel system

Flexible (hose) pipe

0.35-0.531.52-2.104.1-10.321.15-1.50

Losses in distribution systems

Tubewell utilizationNo regulation on irrigation appliances since 1992Density of installation of shallow tubewellsincreasedIrrigated 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 CharacteristicsPotential changes in soil organic matter supply from biomass, soil temp. and soil hydrology

Other changes due to change in temperature andprecipitation 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

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

Water productivity of some crops

Effect on Crop ProductionShallow rooted plants will suffer mostWith 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 SalinityBangladesh has, at present, about 1.0 mha of lands under various levels of salinities which is expected to increase further and extend towards inland

Mapping Unit

Category of salinity (dS/m)S1 S2 S3 S4 S52-4 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

Category of soil salinity and saline areas

Source: SRDI (2000)

Effect on DroughtEvery year, 3-4 million hectares of land are affected by droughts of different magnitudesStress resulting from higher crop ET and reduced rainfall may override any growth benefits from the higher CO2 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 intensitiesA heavy loss to Aman production affects the economy of the farmers

Intensity of drought

Land area,hectare

Yield loss due to drought,%

Very severe 342990 70-90Severe 737028 50-70

Moderate 3154950 30-50

Slight 2867895 10-30

Drought Intensity and yield loss of T. Aman

Effect on FloodsClimate 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 intensitiesThis will threaten Bangladesh agriculture most

Possible Measures for Sustainable Water Use in

Crop Fields

Optimization of Water UseAlready 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 methodHigh 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

Fertigation

Controlled Application of water

Methodsused

Location: Noakhali Location: SatkhiraCrop Yield,

t/haSalinity,

t/haCrop Yield,

t/haSalinity,

dS/mDrip,

raised bed and mulch

Tomato

Water-melon

50-70

40-50

10-12 (4.5-5.5)

10-12(4.5-5.5)

Tomato

Okra

48-55

10-11

9-10(4.75-6.15)

9-10(4.75-6.15)

Traditional method

Tomato

Water-melon

18-20

15-18

10-12

10-12

Tomato

Okra

16-19

5-6

9-10

9-10

Crop production in saline soils

N.B. Figures in parenthesis indicate reduced soil salinity due to improved management practices

Improved distribution systemChannel 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 pattern1. 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

Name of crop Area cultivated,

‘000’ha

Seasonal crop water

requirement, mm

Approx. Irrig. water

requirement, Mm3

Rabi season (October-February)Boro rice 4675 650 759688Wheat 370 300 2018Potato 400 280 2036Maize (w)* 346 450 2831Mustard 547 200 1990Groundnut 70 250 318Vegetables(w)* 448 250 2034Onion 158 230 659Garlic 64 230 266

Sub-total 88121

Annual water requirements of different crops

N.B: (w)* = winter; ** = Supplemental irrigation

Name of crop

Area cultivated, ‘000’ha

Seasonal crop water

requirement, mm

Approx. Irrig. water

requirement, Mm3

Kharif-I season (March-May)T.Aus** 1154 240 6924Vegetables** 231 120 504Maize** 30 100 55

Sub-total 7483Kharif-II season (June-September)Aman rice** 1154 120 3461

Sub-total 3461Grand Total: 99065 Mm3

Annual water requirements of different crops (continued)

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 waterConjunctive 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’ KnowledgeMost of the farmers of the country are illiterate and do not have much idea about consequence of the misuse of irrigation waterThey should be made aware of the water managements in irrigated agriculture through trainings, demonstrations and group discussions

ConclusionsWater 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 countryExisting rules of tubewell installations should be revivedMass media should be used to propagate the water management messages to general people