1

Keywords: rice paddy, multi-utilization of farm land, water resource efficiency, irrigation efficiency,deep-water irrigation

IMPROVING IRRIGATION MANAGEMENTSYSTEMS FOR RICE FARMING

Chun E. KanDepartment of Bioenvironmental Systems Engineering

National Taiwan UniversityTaipei 10617, Taiwan ROC

ABSTRACT

This Bulletin discusses the many challenges facing traditional rice farming, which include: theneed for multi-utilization of farm land; better water resource efficiency; equipment efficiency;lowering of labor costs; and maintenance of ecological functions. In the face of all thesechallenges, there is a need to introduce and promote new irrigation management systems in ricefarming. Some of the recommendations discussed in this Bulletin include: the expansion of ricefarming management scales comprised of human, water, and farmland resources; irrigationresponse strategies during drought; and application of multiple agricultural water resources. Itconcluded by stating that, in view of recent trends in globalization and economic development,the function of agricultural irrigation water is now clustered into: production function; ecologicalfunction; and living function.

INTRODUCTION

Rice paddy is formed by confining wateraround field block borders with short levees.The inflow (irrigation) and outflow (drainage)

Fig. 1. Basic structure of rice paddy.

functions on this mild-sloped land keep thesoil within the borders under saturationconditions (Fig. 1), in which some waterborneeconomic crops, such as rice, or water caltrop,are planted.

2

From the aspect of water, the irrigationwater first flows into field areas throughirrigation systems to provide theevapotranspiration as required by crop growth,as well as the conditions to regulate regionalclimate. It then seeps underground on this vastland to recharge the groundwater, underflow,as well as return flows, then soaks withinborders to form temporary reservoirs to detaindownstream runoff, as well as optimize wetlandto create an intimate space. Finally, thedrainage water discharges into downstreamfarmland to improve the sanitary environmentas well as to provide reuse of return flow,thus, a rice paddy irrigation mechanism iscompleted.

MANAGEMENT SYSTEMSOF RICE PADDIES

Rice paddies have been present since ancienthistory. In terms of promotion of irrigationefficiency, rice paddies can be classified into

Fig. 2. Large-area rice paddies.

two categories by their management scales, oneis the large-area rice paddies as shown inFigure 2, and the other is the small-area ricepaddies as shown in Figure 3. Large-area rice paddies mainly exist in theUSA and Australia, where the land is broadand population density is comparatively low.Rough agricultural management is applied inthese countries as labor costs are high, andfrom land-preparation, seeding, fertilizing, toharvesting, all works are carried out by largemachines, or even airplanes. The advantagesare that the irrigation management is simple,and the labor costs are lower; however, thedisadvantages are that detailed abnormal cropphenomena can not be observed and takencare of, resulting to poor production andquality. Small area rice paddies are focused mostlyin Asian countries, such as Indonesia and thePhilippines. In this case, an irregular shapedrice paddy field is confined by shallow leveesin one single village where water resource is

3

attainable. Another rice paddy field isencircled at lower reach when original cropproduction does not meet the requirement, anda fish-scale type of land use is formed as timegoes by. The advantage is that the irrigationmanagement is simple; however, thedisadvantages are that the areas are small andshapes are irregular, and enormous humanlabor is needed due to low machineryefficiency. Because of the fish-scale land form,no upland crops can be planted during ricecultivation period. In addition, as labor costsare high, this farming type is suitable forfamily or village members, and would beincompatible to the high-efficiency and low-costlarge-area farming type, especially in view ofthe WTO.

CHALLENGES FACING TRADITIONAL RICEFARMING MANAGEMENT SYSTEM

Due to the advent of globalization, the effectsof WTO to rice paddy management in variouscountries are different. There may be moreopportunities for the low-cost yet high-quality

industries, nonetheless, there may be morecompetition pressure on the high-cost yet low-quality industries. As a result, the challengesthat traditional rice farming managementsystems face are discussed according to themulti-utilization of farm land, better utilizationefficiency of water resources, promotion ofequipment efficiency, lowering of labor costs,and maintenance of ecological functions.

Multi-utilization of farm land

The dieting habit has been changing fromsingle main crop to multiple choices, and small-area rice paddy of single crops is fading out.Hence, rice-paddies are modified to medium-sized areas in eastern Asia, such as Taiwan,Korea, and Japan (Fig. 4), where rice paddiesare well planned. Each block has itsindependent irrigation and drainage system,which can be operated individually on its ownplanted crop. However, the freedom to selectcrops to be planted as well as to adoptirrigation and drainage has also broughtdifficulties on irrigation management.

Fig. 3. Small-area rice paddies.

4

Better utilization efficiency of waterresources

In order to promote the efficiency of waterresources utilization, management respon-sibilities and obligations should be clearlydefined. From the concise viewpoint of“supply” and “demand”, the internationallyaccepted terms of “on-farm” and “off-farm”systems, as shown in Figure 5, are introduced.The borderline dividing the two systems isdefined as the water measuring facilities, wherethe off-farm (supply) side is normally operatedby the government or water resourcesauthorities to provide water sources, and theon-farm (demand) side is normally operated byvarious water-use sectors. This concept hasbeen widely accepted internationally, and waterutilization efficiencies due to institutionalproblems are expected to improve.

Promotion of equipment efficiency

It has been a worldwide trend to cost downrice cultivation by using large machineries.

However, it is still a problem for the medium-or small-area rice farming bodies to introducelarge machineries as the lengths of the fieldblocks are too short, thus, the expansion ofmanagement scales seems to be a must forthese areas (Fig. 6). Nonetheless, accompanyingproblems such as dense population, as well asover-dissection of landownership, have shownit to be a rather difficult task.

Lowering of labor costs

The export of farm labor force seems to be acommon trend in the areas of medium or smallmanagement scales. It can be foreseen thatthe need to lower labor cost would be animportant subject, and can start from themanagement of water resources as well asfarming cultivation.

Maintenance of ecological functions

For countries with medium- or small-scalefarms, the interest in managing rice farmingwould lessen as competitiveness weakens

Fig. 4. Medium-area rice paddy

5

Fig. 5. Differentiation between “on-farm” and “off-farm” systems.

Fig. 6. Rice cultivation management of medium- and small-scale farms.

6

under the WTO. However, from the viewpointof national security as well as land protection,rice paddy land is irreplaceable and irreversible.Hence, most governments would make everyeffort to preserve rice paddies. When the area for rice-paddy decreases, theabundant agricultural water resource could bediverted to other purposes. In the meantime,not only the significant agricultural “returnflow” diminishes as the amount of seepagereduces, agricultural production is also affecteddue to water contamination from domestic andindustrial wastes. As a result, the governmentis now promoting the policy of “waterplanting.” In other words, the basic functionsof ponding and irrigating are retained evenduring fallow or when rice is not planted, andthis seems a good choice to reach thesustainable use of farm land.

IMPROVING THE MANAGEMENT OF RICE-FARMING

Among the WTO issues, the withdrawal oftariff and non-tariff trade barriers is a majorconcern. For those industries withcomparatively low competitiveness, sufferingfrom losses or even bankruptcy is a possibilityif the management style or technologyinnovation is not adjusted to upgrade theirglobal competitiveness.

Taking Taiwan as an example, the unevenprecipitation both temporally and spatially hasalways been a headache problem in terms ofwater management. In order to resolve thewater problem among sectors, as well as torespond to the impact of joining WTO, theTaiwan government assists farmers inpromoting fallow by the unit of collectivefarming group (e.g., rotational tertiary block).As all plots in the rotation block of the samewater supply system are covered under thisfallow format, the water conservation effect issignificant. Nevertheless, the fallow behaviorperformed by the random farmers in the non-fallow areas, as shown in Figure 7, drawsconsiderable worries.

According to Japanese experience, thesearea accounts for nearly over 50% of non-fallow area. As the area as well as locationsof this fallow land can not be identified, theestablishment of an effective analyzing model isneeded in order to reach water-saving

purposes. Following are some suggestions onimproving the management of rice-farming.:

Expansion of rice-farming managementscales

There have been plenty of resources inagriculture, however, these resources graduallydiminish due to numerous reasons as explainedbelow.

Human resources. As economy grows, thedemand for living quality and material thingsincreases, and the general low income groupgradually can hardly meet the demand ofyoung generations. The increase in incentiveand job offerings of the nonagricultural sectoralso causes agricultural labor to diversify. Theaging problem among farmers has also becomesignificant, adding to the weakening of thequality and quantity of human resources. Lackof agricultural machineries still exists. In fact,the “man-hunting” problem of the agriculturalsector from the nonagricultural sector isbecoming serious.

Water resources. All civilizations startedwith agriculture, and agricultural wateraccounted for most of the total water resourcesafter all the efforts had been put into theirrigation business. However, in manydeveloped countries, such as Taiwan, Japanand Korea, due to the development of theindustry and businesses, the improvement ofliving standard has led to the demand for morepublic, domestic, as well as industrial watersupply. Again, due to the difficulties ofdeveloping new water sources as well as theenvironmental protest problems, the demand totransfer agricultural water resources tononagricultural sectors has been increasing. In addition to the decrease in quantity as aresult of transferring to nonagriculturalpurposes, agricultural water quality isdecreasing owing to the discharge of domesticand industrial waste water. In many cases,contaminated agricultural water has not beensuitable for irrigation purposes.

Farmland resources. Due to economicgrowth, the demand for city development, cityrenovation, transportation, regional planningdelineation, and other public infrastructure, has

7

led to the transformation of much fine farmland to nonagricultural uses. Although newfarm land is developed, its productivity ishardly as good. Once the farm land resourcesare transformed to nonagricultural uses, theirproductivity can hardly be recovered evenwhen returned to agricultural purposes.Nonetheless, in a free democratic society, thereis no absolute yes or no on public policies,the so-called public of national interest may bethe final judgment, if there is a widely-acceptedstandard. If under proper control, the export ofagricultural human resources is generally anormal process. The necessary effectiveincentive to attract or recruit new generationwith creativity and competitiveness is needed. Once the agricultural water resources aretransferred, the management of farm land withwater shortage would have to adjust. Thepossible measures include adopting waterconservation method, enforcing watermanagement, or quitting agricultural uses. The irrigation system in rice-cultivationcountries such as the USA or Australia hasgreat difference with that in Asian countries.

For example, the agricultural states are vast infarm land and low in population density. Thatis, each farmer owns enormous farm land, thecultivation style is rough in which landpreparation, seedling, fertilizing, or harvestingare carried out by machines. Although theunit area production and crop quality at cannot compete with those in the Asian countries,their low cost is a big advantage. By the timewhen better production and quality arereached, the agricultural products from Asiancountries will loose their competitiveness. With the advent of the WTO, farmers'interest in planting rice has been decreasing,and rice paddies are expected to be deserted.Under this circumstance, the original irrigationwater may be wasted. The followingsuggestions are proposed for reference as wellas discussion. In Asian countries, agricultural managementis normally based on families in which thefarming scales are mostly small. Hence, there isa need to design a series of accompanyingrewards and controlling measures by providingenough incentives so that a collective area offarm land is formed by uniting several farmers’

Fig. 7. The problem of fallow.

8

land by means of leasing. The farming practiceof this collective land is conducted by anexpert organization, adopting the similar roughfarming like that of the USA in order to reduceproduction cost and to promotecompetitiveness. As long as the legislativeand controlling measures are appropriate suchthat people’s interests are not harmed, not onlythe impact of WTO on rice paddy could bereduced, but the cultivation techniques couldbe improved to increase rice quality for furtherexport opportunities. Once the small farm lands are collected andconcentrated, the ridge borders as well as thesmall ditches in between blocks will be leveled,and the cultivation area could be increased aswell. In other words, agricultural machinerycould be introduced, and production could beincreased consequently. In addition, thenumber of gate operation by the watercontrollers would be greatly reduced, and theirrigation management efficiency would behighly promoted. It is believed that under theprofit incentive conditions, more people wouldparticipate in agricultural scientific research, andthe extension of agricultural and irrigationtechnology worldwide is expected. The current irrigation management in themedium-scale rice paddies has the merits of

Fig. 8. Expansion of rice-paddy management scales

independent operation, however, irrigation anddrainage practices are sophisticated thatconsiderable labor is needed to control thegate operations, and are economicallyinefficient considering that labor costs are highthese days. As a result, a new rotationalblock with an overflow type of irrigationditches which have higher outer ridge wallsand with eliminated inner ridge walls isproposed, as shown in Figure 8. This type ofrotation blocks with overflow ditches couldnot only promote farming efficiency, but alsoreduce labor costs. In addition, low efficiencyproblems of introducing large machineries arealso resolved. In order to solve the confusion of landownership problems when plot ridges areeliminated, a delineation method by installingmarking posts is proposed, as shown in Figure9. With these marking posts, there would belittle property dispute problems, more farm landfor crops, and higher efficiency for agriculturalmachinery operations. As for irrigation efficiency problem, theconcept of deep-water irrigation cultivationtechnique can be introduced. This is toprovide rice crop with the right amount ofirrigation water when precipitation is plenty.The number of irrigation practice could be

9

reduced, and irrigation efficiency could beupgraded. In the meantime, the effectiverainfall ratio as well as conveyance lossproblems can be effectively resolved. For example, before 1945, the rice-paddyirrigation water depth in Taiwan followed theJapanese rule of 6 cm. In 1994, the rice-paddywater depth has been raised to 18 cm, thenfurther to 25 cm by 2001. In Taiwan, somerules have been followed consistently for 60years. The reaction of people when they firstheard about the term “deep-water irrigation”was the survival of the plant under 25 cmdepth of water, if it would get drowned duringthe seedling period. As a matter of fact,“deep-water irrigation” does not start with 25cm of water depth at the very beginning.Instead, the water depth is raised graduallyaccording to the growth of the crop. In otherwords, the true meaning of deep-waterirrigation is the maximum water depth the fieldstructure could sustain, as shown in Figure 10. Taiwan has been suffering from frequentdroughts recently, so the promotion of deep-water irrigation seems a conflicting idea.Agricultural water is already insufficient for the6-cm depth irrigation, not to mention the deep-

water irrigation. But the fact is, since thetemporal distribution of rainfall is uneven, ifthe excess water during rainfall season couldbe stored in the vast rice-paddy field, thepercentage of agricultural water in thereservoirs could be significantly reduced. Thiscan be exemplified by the 350 thousand acresof rice-paddy field in Taiwan, the volume ofthe excessive 19 cm depth of water, equivalentto 665 million tons of water, is greater that anyof the reservoir capacity in the island. Whenever rice growth is not affected, waterresources, which would normally be dischargedto the sea, is diverted and stored in the paddyfields. When water shortage occurs, irrigationpractice could hold for some time. Furthermore,the utilization efficiency may be increased bytransferring the stored water downstream foragricultural or other purposes In irrigation management, as the irrigationwater depth in deep-water irrigation could beincreased to 250 mm, the estimated rotationalirrigation period could thus be lengthened toaround 20 days. When the idea of the above-mentioned large-area farms is introduced, thework load of the water controller could bereduced to 1.25 day each time, the irrigationcost is greatly reduced, and the rice price

Fig. 9. Delineation of land property by marking posts.

10

would be more globally competitive.Furthermore, if more efforts as well as researchare put in, such that a rice species moresuitable to deep-water irrigation, and withbetter quality and quantity, the feasibilitywould be even more favorable.

Irrigation strategies during droughts

The rice-paddy field is like a “natural reservoir”with vast area although shallow in depth, andshould be carefully utilized. When the“excessive” agricultural water is stored in thisnatural reservoir, it would be recharginggroundwater, underflow, and return flowcontinuously. The way the irrigation practiceconsumes water is simply to provideevapotranspiration needed for normal growth,and is far different from those of industrial anddomestic water. Consequently, from theviewpoint of effective use of water resources,the introduction of water to be stored in therice field during wet seasons should beencouraged without restrictions. In other word,water conservation during wet season whenwater is abundant is meaningless. Instead,how to retain excessive rainfall water in therice field for operation purposes, to maintain

appropriate seepage, to increase groundrecharge, to reduce irrigation management cost,and to create a water-friendly environment, arein fact the reasonable ways to manageirrigation water. The current irrigation water distributionstrategy to aid industry by agriculture (Figure11) is to include the industrial body as anormal operation unit in the IrrigationAssociation System. When water shortage ordrought occurs, the industrial water demand isfirst fulfilled. Agricultural water distributionmeasures are then applied according to thedrought-endurance of the crops (however, thisscenario can be applied only occasionally assaline problem may be unfavorable for thesustainable development of farm land). Andwhen extreme severe water shortage occurswhen the industry could not get what itneeded even when complete fallow is carriedout, emergency measures such as drilling deepwell in river bed are required. The condition of the plan is solely basedon the existence of agriculture. Once theagricultural water right is decreased underpressure from various sources, the lack offlexibility may lead to a worst case that eventhe emergency withdrawal of groundwater isinoperable because the recharge is too few.

Fig. 10. True meaning for deep-water irrigation

11

Application of multiple agriculturalwater resources

The increase in industrial and domestic waterdemand due to the development of economyas well as change in industrial structures hasput pressure on agricultural water. Moreover,as the development of water resources isbecoming difficult, especially with the adventof the WTO, how to effectively distribute andmanage water resources has become an urgentissue. As agricultural water used to accountfor most part of the water resources in almostevery country, a comprehensive waterresources policy and regulations are needed.In the future, the goals for agricultural waterwould be “ecology, living, and production.” Infact, the benefits of paddy fields in ecologicaland living functions are far greater than theirproduction functions, and their roles could notbe ignored. The beneficiaries include not onlythe low-income farmers, but the entire people.Consequently, the agricultural business muststress on sustainable management in order notonly to provide sufficient and safe food, butalso for the sake of long-term national security.It is, thus, urged that rice-paddy fields and

Fig. 11. Scenarios of agriculture aiding industry.

agricultural water need to be rationally securedand protected. Although shallow in depth, the agriculturalarea is a “natural reservoir”, and should beproperly used. Unfortunately, some peoplesuggest to increasing water of other sectors bycutting down agricultural water simply becauseagricultural production value is lower, rice-planting area is decreasing, and consequentlythe application of water would be less. Bydoing this, only the ratio of effective use ofrainfall has decreased, and it is definitely notan effective use of water resources. An idea of leasing the fallow areas to thegovernment or industries in order to convert toponds for water storage purposes could beconsidered. The surface water storage wouldnot be reduced because of the decrease in riceproduction; the functions of climate adjustment,groundwater recharge, as well as floodreduction could be retained. In other words,the conventional purpose of rice paddyirrigation is transformed from production tojoint functions of production, living, andecological. By introducing more water during wetseasons, the stored water in paddy ponds

12

Table 1. Three functions of agricultural irrigation water

Function Items

Production function 1. Increase production per unit area2. Increase cultivation area3. Avoid damages of continuous cropping4. Improve field soil by settling silts in the irrigation water5. Maintain soil productivity

Ecological function 1. Replenish groundwater resources2. Stabilize river flow3. Flood control by reducing peak flow (paddy fields as

reservoirs)4. Mitigate land subsidence5. Maintain clean water quality; purify air7. Adjust micro-climate8. Prevent soil erosion9. Desalt10. Conserve wetland, and provide sanctuary for water birds11. Water resources cycles

Living function 1. Improve living environment and sanitary of farms2. Provide miscellaneous water and fire hydrant in farms3. Aid domestic water supply during water shortage4. Promote communication and cooperation among villages via

management organization systems5. Provide comfortable living environment and fair scenery6. Provide leisure of cultural education7. Stabilize people’s living

stays “running”, and provides the best“wetland” ecology for animals as well asplants, groundwater recharge, andenvironmental conservation, etc. The runningwater also improves the rural sanitation, createsa friendly environment for farms or villages,and satisfies the demand for the joint functionsof production, living, and ecological. Inaddition, as the utilization ratio is high, thisponded water could not only provide theauxiliary water sources for miscellaneouspurposes in normal time, but could also extendavailability in times of water deficit duringdrought. From the viewpoint of the three jointfunctions of paddy field, the effective use ofwater resources, and the maintenance ofsustainable productivity of soils, and in orderto provide the basic income for farmers withoutchanging yet improving the current paddy fieldstructures, the directions for future agriculturaldevelopment may include:

A. Maintaining the contribution of ricepaddy production;

B. Strengthening the functions of paddyfields to living and ecological;

C. Emphasizing the meaning of rice paddyirrigation to effective use of waterresources as well as the maintenance ofsoil productivity; and

D. Finding a solution to irrigation water bymaking fully use of fallow areas.

Conclusion

The society has been evolving, and everybusiness nowadays has to keep in pace inorder achieve sustainable and multidirectionalmanagement of resources. Hence, the role ofagriculture in the society is not simply theproducer; it now has a multidirectional role, asshown in Table 1 on the three functions ofagricultural irrigation water. Taiwan has joined the WTO in 2001, andthe impacts of low-priced agricultural productsand cancellation of tariff protection follow.These impacts cannot be ignored in view ofthe fragile agriculture in island, and aresimilarly difficult for the countries with smallfarm land area as well as expensive laborcosts, namely Japan and Korea. How to facethe crisis, and to quickly propose effectiveresponse measures, are the urgent tasks for thegovernments.