Rice and water

Crop and Environmental Sciences DivisionCrop and Environmental Sciences DivisionInternational Rice Research InstituteInternational Rice Research Institute

Los BaLos Bañños, Philippinesos, Philippines

• 95% of the world’s rice is produced in Asia• 75% of rice produced is irrigated (75 m ha)

• Irrigation in developing countries: uses 80-90% of fresh water developed In Asia: > 50% of this is for rice

• Rice requires much water: 3000-5000 l kg-1 rice• Rice receives 34-43% of world’s irrigation water• Rice receives 24-30% of world’s developed fresh water • Rice is biggest single ‘user’ of developed fresh water

Irrigated rice and water

0

50

100

150

200

250

300

World irrigated area Asia irrigated area World irrigated rice area

106 ha

0

1000

2000

3000

4000

World water withdrawal World water use in irrigationRice water use in irrigation

km3

Why does rice require so much water?Why does rice require so much water?

Field water balance lowland riceField water balance lowland rice

Computing water balanceComputing water balance

Input – outputs = storage change

Neglect storage change: Inputs = outputs

Irrigation + rainfall = seepage & percolation + evapotranspiration

Measure (weir, flume, flow meter)

Measure (rain gauge)

Calculate (Penman, pan evaporation)

“Rest term”

Daily (mm d-1) Season (100 d)

Land preparation 175-750

Evapotranspiration

Wet season

Dry season

4-5

6-7

(30-40% evaporation)

400-500

600-700

Seepage & percolation

Heavy clay

Loamy sand

1-5

25-30

100-500

2500-3000

Water requirements in lowland riceWater requirements in lowland rice

Total season : 675-4450 mm Typical value : 1300-1500 mm

Water (mm) SP (mm d-1)

ZIS (Wuhan)• Experiment• Farmers• Mezo site

750-1150

650- 940

750-1525

4.0-6.0

1.6-2.8

4.0-8.0

Shimen (HZ)• Early• Late

850-950

575-700

1.0-6.0 (3.8)

1.0-6.0 (3.8)

Examples water use; China 1999-2000Examples water use; China 1999-2000

Water (mm) SP (mm d-1)

Guimba 88

89

90

91

2197

1679

2028

3504

18.3

12.5

16.4

32.8

Muñoz 91 1019-1238 5.2-7.6

Talavera 93 577- 728 0.3-2.0

San Jose 97 2874 25.8

San Jose 96

97

1417 (DS)

1920 (DS)

9.6

15.2

PhilRice 01 600 1.1 (-> 4.4)

Examples water use; Philippines 1988-2001Examples water use; Philippines 1988-2001

Groundwater: a “hidden” source of Groundwater: a “hidden” source of waterwater

-100

-80

-60

-40

-20

0

20

18 38 58 78 98 118Day number

Groundwater depth (cm)

Tuanlin, China, 2002

-100

-80

-60

-40

-20

0

20

168 193 218 243 268 293

(cm)

Flow ering HarvestPanicle initiation

Groundwater depth (cm)Day number

Changle, China, 2002

-300

-260

-220

-180

-140

-100

-60

-20

20

3727

0

3727

7

3728

4

3729

1

3729

8

3730

5

3731

2

3731

9

3732

6

3733

3

3734

0

3734

7

3735

4

3736

1

3736

8

3737

5

Groundwater depth (cm)

Dolores, Philipines, 2002

Direct uptake of water by plant roots

Where do the outflows go?Where do the outflows go?

Evaporation and transpiration: unrecoverableOverbund flow, seepage, percolation: reusable

Pokhara, Nepal, 2006

Surface and subsurface water flows across a toposequence of rice fields. D = drainage (over-bund flow); I = irrigation, P = percolation; S = seepage.

N

MAP OF WENJIAXIANG SITE IN CHINA

N

TanksGPS Measurements points

Boundary

Irrigation Canals

Drainage CanalsRoads

Ju zh an g R

i ver

Dangyang Ci ty

Zhi jiang Ci ty

Yangtze River

Zhanghe Reservoi r

Zhanghe Project Administration*

Th e

Fir s

t M

ain

Can

a l

Jiangl in Ci ty

Shashi Ci ty

Jinmen City

*Wenjiaxiang

Zhongxiang Ci ty

*Tuanlin

*Shayang Ci ty

Changhu Lake

The Fourth Main Canal

General Main Canal

Z H A N G H E I R R I G A T I O N D I S T R I C T

Designed Irrigated areaCatchment area reservoirArea with supplementary Irr igation, prone to flooding

RiversReservoirs

Main Irrigation canalsIrrigation canalsDrainage canalsNatiral streams

Railway trackRoads

Cities

IW MI - J ANU ARY 20 0 0

So ur ce : Zha ng he Pro ject Adm inis tra tio n De ce mb er 19 86

Water re-use through reservoirs and on-farm pondsWater re-use through reservoirs and on-farm ponds

UPRIIS irrigation scheme, UPRIIS irrigation scheme, Philippines Philippines District I: 18,000 haDistrict I: 18,000 ha

Increased production withincrease in scale, usingsame amount of irrigation

Water re-use by pumps:• 18% farmers• 23% area• 10% water reused

Reuse surface water by small dams• 45% water reused

y = 0.0046x + 0.8885

R2 = 0.9049

y = 0.0013x + 1.1412

R2 = 0.9174

0

10

20

30

40

50

60

70

80

90

100

0 5000 10000 15000 20000

Water reuse (106 m3)

Area (ha)

Water reuse by check dams in creeks/drains (♦) andby pumping from shallow groundwater (◊)District I, UPRIIS, Philippines, 2002

Water productivity (WP)Water productivity (WP)

Amount of grain produced per unit of water usedkg grain m-3 water

What water used?

WPT : water transpiredWPET : water lost by evapotranspirationWPI : water put in by irrigationWPIR : water put in by irrigation and rainfall

Start counting water at land preparation or at crop establishment

Water productivity

(kg grain m-3 water)

Rice Dryland cereal

Per transpiration (T) 1 up to 2 wheat: up to 2

Per evapotranspiration (ET) 2 0.6-1.6 (1.1) wheat: 0.6-1.6

maize: 1.1-2.7

Per inputs by rain and irrigation (RI) 2

0.2-1.2 (0.4)

Water productivity (WP)Water productivity (WP)

1 : measured in pots2 : measured in fields

0

5

10

15

20

25

30

35

0.0-

0.1

0.1-

0.2

0.2-

0.3

0.3-

0.4

0.4-

0.5

0.5-

0.6

0.6-

0.7

0.7-

0.8

0.8-

0.9

0.9-

1.0

1.0-

1.1

1.1-

1.2

1.2-

1.3

1.3-

1.4

1.4-

1.5

1.5-

1.6

1.6-

1.7

1.7-

1.8

1.8-

1.9

1.9-

2.0

2.0-

2.1

2.1-

2.2

2.2-

2.3

2.3-

2.4

2.4-

2.5

Frequency (%)

WPET

0

5

10

15

20

25

30

35

0.0-

0.2

0.2-

0.4

0.4-

0.6

0.6-

0.8

0.8-

1.0

1.0-

1.2

1.2-

1.4

1.4-

1.6

1.6-

1.8

1.8-

2.0

2.0-

2.2

2.2-

2.4

WPIR

Frequency (%)

Zwart and Bastiaans, 2005

Tuong, Bouman, Mortimer, 2005

• Rice plant same WPT as other C3 cereals• Rice field same WPET as other C3 cereals Variation in WPET caused by variety, climate, management

• Rice field requires 2-3 times more water than other cereals, mainly because percolation and seepage losses (25-50% in heavy soil with shallow groundwater, to 50-85% in lighter soils with deep groundwater)

• Percolation and seepage are/can be reused downstream

Some conclusionsSome conclusions

Pressure to produce more food (rice) is getting

greater because of ever increasing population

But also:

More people want• more industry• more drinking water• more cities• more swimming pools• more….

=> Water is getting scarce and expensive

Need to develop technologies to help farmers cope with water shortage (ie, not enough water to keep rice fields continuously flooded)

Water-saving technologies