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![Page 1: Rice and water Crop and Environmental Sciences Division International Rice Research Institute Los Baños, Philippines.](https://reader036.fdocuments.us/reader036/viewer/2022062421/56649e405503460f94b32479/html5/thumbnails/1.jpg)
Rice and water
Crop and Environmental Sciences DivisionCrop and Environmental Sciences DivisionInternational Rice Research InstituteInternational Rice Research Institute
Los BaLos Bañños, Philippinesos, Philippines
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• 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
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World irrigated area Asia irrigated area World irrigated rice area
106 ha
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World water withdrawal World water use in irrigationRice water use in irrigation
km3
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Why does rice require so much water?Why does rice require so much water?
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Field water balance lowland riceField water balance lowland rice
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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”
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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
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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
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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
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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
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Where do the outflows go?Where do the outflows go?
Evaporation and transpiration: unrecoverableOverbund flow, seepage, percolation: reusable
Pokhara, Nepal, 2006
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Surface and subsurface water flows across a toposequence of rice fields. D = drainage (over-bund flow); I = irrigation, P = percolation; S = seepage.
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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
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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
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y = 0.0046x + 0.8885
R2 = 0.9049
y = 0.0013x + 1.1412
R2 = 0.9174
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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
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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
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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
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0
5
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30
35
0.0-
0.1
0.1-
0.2
0.2-
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0.3-
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0.4-
0.5
0.5-
0.6
0.6-
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0.7-
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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
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• 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
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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
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Need to develop technologies to help farmers cope with water shortage (ie, not enough water to keep rice fields continuously flooded)
Water-saving technologies