AGRICULTURAL WATER DEMAND PREDICTION MODELBY USING INPUT-OUTPUT TABLE WITH IMPACTS FROM DECLAREDSTRATEGY OF THAILAND
Pongsak SUTTINON, Nasu SEIGO
Kochi University of Technology
ABSTRACT: Agricultural sector is one of the main water consumers in Thailand including irrigation andlivestock. Irrigation water demand model was developed into 2 scale; Thailand and provincial scale. Main
crops in study area are only major rice, second rice, and sugarcane because of constraint of soil types.
Thailand crop area was analyzed from situations of world and domestic market including gross domestic
product in agricultural sector, cost of production factor, and unit crop price. It is certain that Thailand
irrigation area will be decreasing because of urbanization. In provincial scale, crop area depends on trend of
Thailand and economic situation in each area including the constraints such as; soil condition, possible
agricultural area, irrigation service area of governmental agencies, and risk of climate. In case of normal
rainfall year, agricultural water demand in Lower Chao Phraya River Basin is 2,195 MCM in year 2025.
Irrigation sector is the main user with 2,141 MCM or 97 % of total agricultural water demand.
KEYWORDS: agricultural water demand prediction model, Input-output table
Agricultural sector is main part of export value in

1. INTRODUCTION

Thailand with approximately 20 % of total. In theThailand is basically agricultural country. Mostworld, Thailand is the main exporter of agricultural

people located in rural area mainly work in irrigation

product as following; the 1st order in rice, cassava,activities. From this reason, agricultural sector is one

and maize; the 4th order in sugarcane. Thailandof the important economic activities in Thailand.

declared national master plan name “Thailand is theGross Domestic Product or GDP growth rate in

kitchen of the world” in the 9th national economic

agricultural is low comparing with non-agriculturaland social development plan. From this policy, foodsector because of master plan concentrated industrial

and beverage products were concentrated withand service development in the past. However, GDPhigher demand of raw material from agricultural

growth rate in this sector is constant even in thesector.

economic crisis in year 1997. In that period,industrial sector faced the high impacts withIn the viewpoint of water use, agricultural activities

critically decreased GDP growth rate. After theconsume much water especially rice which is maineconomic

carefully

crop of Thailand. Only 1 % of consumed water inconcentrates in agricultural sector again as shown inthis sector is a big amount of water in industrial andcrisis,

Thaithgovernment
thsome strategy of the 9 and 10 national economic

household sector. Policy makers should carefully

and social development plan.

consider this part with the other users. Water sharefrom one sector to another is very sensitive. It may

change the water shortage problem to bigger

Where, WDcrop is irrigation water demand, ETcrop isproblem as society and political problem.

the water requirement in each crop, Pe is effective
rainfall, and Acrop is the crop area.

1.1 Objectives
The main objective of this chapter is to developWorld situation of agricultural was considered

agricultural

byusingbecause Thailand is the main exporter in the world.

effects

fromFrom this reason, the main effects of irrigatedchanging economic structure with the effect ofdemand from Thailand were 2 factor; (1) world

climate factors.

market, and (2) domestic market.

waterdemandinput-output model

tomodelcalculate

In term of product of main crops in the world, theStudy area
The study area is located in Lower Chao Phraya

growth rates of each product were graduallyRiver Basin. There are 7 provinces in this area;

increasing. One of interesting points is that the yield

Ayutthaya, Bangkok, Nakon Pathom, Nontaburi,of each crop. Trend of yield or product per area isPathum Thani, Samut Prakan, and Samut Sakhon as

increasing in case of the world because of high

AYT, BKK, NKP, NTB, PTT, SPK, and SSK.

technology and knowledge used to harvest. At thesame time, the yield of each crop in Thailand islower than the average world value except second

2. METHODOLOGY

rice and cassava.
The model mechanism of agricultural water demand
management model developed is shown in figure 1.

In case of major rice, yield in Thailand is only 60 %The model was divided into two parts; irrigation andof average world yield. There are many reasons are

livestock water demand.

following; type of rice, hydrological and climate
factors, irrigation method, etc. However, this gap
between Thai yield and the world yield shows

2.1 Irrigation water demand
waspossible yield to increase. If the yield in Thailand isdeveloped in national scale to calculate main crop

higher, farmer can produce more products at thearea affected form world market and domestic

same area and water but gets more benefit. Form thismarket in Thailand with Input-output table model.

point, high productivity is one of the interesting

Secondly, main crop area in each province wasmeasures to increase the value of used water incalculated from economic structure with trend of

irrigation sector.

Firstly,irrigationwater

demandmodel

Thailand under constraints of possible agriculturalarea, irrigation service area, and soil condition.

The main crop concentrated in this model are major

Thirdly, water use unit in each crop was analyzed

rice (regular rice was planted in rainy season and use

with climate effect under uncertainty of rainfall inmainly rainfall), second rice (rice was planted in

the future. Finally, irrigation water demand wasother seasons and mainly located in irrigation service

calculated from forecasted main crop area and waterarea or close to water source), maize, cassava, anduse unit per area by using the following equation:

sugarcane. Now the agricultural area in Thailand isgradually decreasing form the past 20 years because

WDcrop= (ETcrop - Pe) * Acropof urbanization.

Water Demand Management Model in The Lower Chao Phraya River Basin, Thailand

Agricultural water demand management model
Industrial water demand
management model

Domestic water demand
management model

Irrigation water demandmanagement model

Livestock water demand
management modelWorld market and nationalsituation

National situation

Input-output table model with economic scenarios

Changing economic
structure

Population model

Water use analysis in each source

Industrial water demandprediction model

Domestic water demandprediction model

Irrigation water demandprediction model

Livestock water demandprediction model

Water supply master plan in each water source with constraints in provincial scale

Governmental option scenarios-Equilibrium analysis
Water demand-supply curve
Pricing policy(Impacts to Thai economic structure )Strategic decision making model(investment of infrastructure under
uncertainty of water demand in the future)

Toolbox of integrated water demand management model with water and benefit share analysis

Figure 1. Model mechanism.

However, Royal Irrigation Department (RID) plan tonontaburi, Samut Prakan, and Samut Sakon are

construct more water infrastructure for irrigationindustrial and service area. The land cost in this area

service area. From this reason, the planted area of

was rapidly increasing. The agricultural area wassecond rice is increasing.

sold and change to industrial and inhabitant use.

In study area, rice is the main crop because of

Crop water demand is usually measured in terms ofphysical condition of soil. The main producer in thisevapotranspiration. This rate depends on climate

study area is Ayuttaya province on the upper part. It

factors such as temperature, radiation, wind speed,

is interesting that rice farm in the lower part of study

precipitations, soil moisture, surface properties andis much lower than the upper. The reason is that theetc. crop water requirement are estimated onmain activities in lower part including Bangkok,

reference crop evapotranspiration or ET0. ET0 is themaximum

evapotranspiration

ratethat

theTable 1.

Water requirement in each crop in study

atmosphere is capable of extracting from aarea.

well-watered field. Methods of estimating ET0

Possible crop inETcrop ,depends on conditions and constraints in each area.

study area

water requirement in each crop; mm.

The water requirement in each crop can be estimatedMajor rice1155

as follows:

Second rice

1155

Sugarcane

1632

ETcrop= Kc * ET0(Source: RID)

Where, ETcrop is the water requirement in each crop,Finally, irrigation water demand was calculated from

Kc is crop coefficient, ET0 is the maximum

summation of water in each crop as following.

evapotranspiration. Royal Irrigation Department(RID) collected related data and calculated the waternWDirri = ∑ ( ETcrop − Pecrop ) * Acrop

requirement as shown in table 1 by using modified

crop =1

Penman-Monteith method recommended to besuitable with climate and hydrological factors ofWhere, WDirri is irrigation water demand, ETcrop isThailand.

the water requirement in each crop, Pe,crop is effective
rainfall, Acrop is the crop area, Crop is possible crop

Water use unit per crop area is shown in term of

in study area; major rice, second rice, and sugarcane.

(ETcrop - Pe). Pe or effective rainfall is excess rainfall
or precipitation that is converted to runoff. However,Table 2.

effective rainfall in each crop depends on crop

Rainfall data and rainfall scenario.

Raw data

New arranged data

Percentile

pattern. Major rice was planted from the starting ofYear

Rainfall, mm.

YearRainfall, mm.

rainy season or July and harvested in the end of

1994

1,716

2004

1,308

0.0

December but the second rice was planted from

1995

1,639

2003

1,384

15.7

February to May. Farm crops can be plant in the1996

1,681

1997

1,404

19.9

whole year.

1997

1,404

1998

1,449

29.2

1998

1,449

2002

1,548

49.7

Finally water use unit per crop area was calculated

1999

1,780

1995

1,639

68.5

by using data of water requirement in each crop and

2000

1,791

2001

1,680

77.0

effective rainfall. However, irrigation sector is an2001

1,680

1996

1,681

77.2

activity that highly depended on rainfall factor. From

2002

1,548

1994

1,716

84.5

this topic, uncertainty in rainfall in the future was

2003

1,384

1999

1,780

97.7

considered as rainfall scenarios in table 2. This table

2004

1,308

2000

1,791

100.0

was analyzed from rainfall data in the past and made(Source: edited from Thai Meteorological Department)

20th

50th

80th

the order from the lowest to the highest value to findthe rainfall depth in each percentile. In this scenario,
20th percentile was defined as low rainfall year. The
50th percentile and 80th percentile are normal andhigh rainfall year.

2.2 Livestock water demand
Livestock sector is very low percentage if comparing
with irrigation sector but the important point isenvironmental viewpoint. Wastewater from livestockin high density area such as Nakon Pathom isinteresting topic for policy makers. The forecasting(1) Decreasing crop area: major rice, maize, andcassava

method in this sector is basically trend analysis form

This situation is as same as the present trend. Thethe data in the past. Water use unit per livestock was

irrigation area is decreasing because of urbanizationcollect from Department of Livestock Developement. in Thailand. The irrigation area was changed toFinally, livestock water demand was calculated fromindustrial and inhabitant area especially in Bangkok

forecasted number of each livestock and water use

and vicinities.

unit per head.

(2) Increasing crop area: second rice and sugarcane
This increasing crop area is second rice because theexpansion of irrigation service area. Farmers can use

3. RESULTS

same area to plant rice by twice a year with
3.1 Irrigation water demand model

supported water from irrigation system. In case ofThailand crop area model was developed in nationalsugarcane, there is more demand from international

scale with dimension of time series or matrix of 5 X

with higher price of sugarcane.

20 (5 major crop with 20 years) in forecasting step.
The equation of model was shown as follow.
A_TH(crop,t) = C1(crop) * GDP_AGR_WR(t)+ C2(crop) * GDP_AGR_TH(t)+ C3(crop) * CO_Fe(t-1)+ C4(crop) * CO_In(t-1)+ C5(crop) * PR_WR(crop,t-1)+ C6(crop) * PR_TH(crop,t-1)
Where, A_TH(crop,t) is Thailand crop area in each

Figure 2. Planted area of main crop in national scale.

crop and forecasting year, C (prov) is constant ineach crop, GDP_AGR_WR(t) is world gross

Provincial crop area model was developed withdomestic

sector,dimension of time series or matrix of 7 X 20 (7domestic

provinces with 20 years) in forecasting step. The

product

GDP_AGR_TH(t) isin

agriculturalThailandgross

product in agricultural sector, CO_Fe(t-1) is cost ofequation of model was shown as follow.

fertilizers in last year, CO_In(t-1) is cost ofinsecticides in last year, PR_WR(crop,t-1) is world

A_PR(crop,prov,t) = C1(prov) * A_TH(crop,t)unit price of each crop in last year, PR_TH(crop,t-1)+ C2(crop)*GDP_AGR_PR(prov,t)

is Thailand unit price of each crop in last year, crop

/GDP_AGR_TH(t)consists of major rice, second rice, maize, cassava,and sugarcane.

Where, A_PR(crop,prov,t) is provincial crop area
in each forecasting year, A_TH(crop,t) is Thailand

Figure 2 shows planted area of main crop forecasted

crop area in each crop and forecasting year, C (prov)

in Thailand scale. The results can be divided into

is constant in each crop, GDP_AGR_PR(t) is gross

two groups;

provincial

product

inagricultural

sector,domesticcompleted. Without new development plan, it can beproduct in agricultural sector, crop consists of major

said that there is no more irrigation service area inrice, second rice, and sugarcane, prov consists of 7

this area. Figure 4 shows constant of crop area

provinces in study area. The constraint consists of 1)

outside irrigation service area.

GDP_AGR_TH(t) isThailandgrossSoil condition of each crop and province, 2) Possible
agricultural area, 3) Inside and outside irrigation
service area of RID.
The results can be divided into two groups;(1) Case of inside irrigation service area
In this case, high percentage of crop area is major
rice and second rice because of physical soil
condition of clay. Only sugarcane was planted in
Nakon Pathom. The ratio of major and second rice isequal because of completed irrigation service area inFigure 4. Planted area of main crop outside irrigationthese 7 provinces. However, the irrigation area ofservice area.

major rice is decreasing because of urbanization but
crop area of second rice is increasing to as same

Figure 5 shows Irrigation water demand of mainlevel as major rice because of completed irrigation

crop in case of normal rainfall year. Actually, water

service area as shown in figure 3.

requirement of second rice is as same as major rice
but major rice was planted in rainy season with higheffective rainfall. Form this reason; water demand
for major rice is less than case of second rice. Themain water consumer in this area is second rice
approximately 65 % of total.
3.2 Livestock water demand model
Livestock water demand was calculated fromforecasted number of each livestock by using trend
analysis and fixed water use unit per head of each

Figure 3. Planted area of main crop inside irrigation

livestock in study area. The main water consumers

service area.

are swine and chicken concentrated in Nakon
Pathom approximately 75 % as shown in figure 6.

(2) Case of outside irrigation service area
The lower part of study area is mainly industrial and

3.3 Agricultural water demand model

inhabitant area. Form this reason; there is no

Agriculturaldevelopment of irrigation project. In the upper partirrigation and livestock water demand. Figure 7of 7 provinces, there are many rice fields mainly inshows agricultural water demand in normal rainfall

Ayuttaya province. Many irrigation projects areyear.

located in this area and most of them are alreadywater

demandissummationof

(a.) Total irrigation water demand(b.) Provincial scale

Figure 5. Irrigation water demand of main crop in study area in case of normal rainfall year.

(a.) Total irrigation water demand(b.) Provincial scale

Figure 6. Livestock water demand in study area.

(a.) Total agricultural water demand(b.) Provincial scale

Figure 7. Agricultural water demand in study area in case of normal rainfall year.

In agricultural topic, irrigation water is the main

only water users in each sector such as factory,

water consumer approximately 97 % of total demand. farmer, and the head of citizen located in that area.
The upper part of study area is high water user inThe officers form local-central government andagricultural sector because of irrigation society.

specialists from academic fields play a role as onlyconsultants. By this method, the right and sharing ofwater and benefit was designed by water users. The

4. CONCLUSION

suitable solutions are generally buying / leasing /Proposed agricultural water demand model canselling water right with satisfying received benefit.

forecasted water demand in irrigation and livestock
sectors. Irrigation water demand model is function ofREFERENCES

crop area and water use unit per area in each crop.
National crop area model was firstly analyzed withP. SUTTINON., 2008. Water Demand Management

situations of world and Thailand market such as

Model in Lower Chao Phraya River Basin, Thailand,

GDP in agricultural sector, cost of insecticides &PhD Dissertation, Kochi University of Technology,

fertilizers, and unit price of agricultural product.

Kochi, Japan.

Provincial irrigation water demand was calculated byusing function of Thailand crop area and ratio ofRoyal Irrigation Department. (2003). The Project ofGPP and GDP. Water use unit was calculated by

9th Water Resources Master Plan and Irrigation

evaportranspiration and effective

Projects: Chao Phraya River Basin.

rainfall withscenario of high, normal, and low rainfall year.
Livestock water demand was predicted by using

Thai Meteorological Department. (2007). Climate

trend analysis. In this study area, irrigation is main

data of Thailand, URL: http://www.tmd.go.th/ (lastsector that need high percentage of water.

date accessed: 12 December 2007).

5. RECOMMENDATIONThe next interesting topic is how to manage thewater share of each user and activity with thechanging economics structure from declared policy?
The water rights and sharing in the dry season arealways the critical period for water shortage problem.
Water management system in Thailand is generally
planned from the top-bottom or from central
government to users. The problem of this method isthat right of water in each user was designed andcontrolled by policy makers that don’t use water inthat area. One interesting measure used in Japan isbottom-topmethodor

planning

from

local

committee of each area. The committees consist of