Water management practice in rice fields directly affect the production of paddy. Components of warer requirements in rice fields, espe cially during the dry season, should be thoroughly identified in order to make efficient use of water, because very little research has been done and there is still lack of knowledge regarding the water consumption mechanism in tropical Asian countries. For this purpose experiments were conducted on two commonvarieties of rice in the central plain of Thailand. Evapotranspiration andpercolation losses were computed separately on daily basis for the entire cropseason from each field. The practice of mid-term drainage was adopted insome fields, and it was observed that this practice helped in increasing yield ofpaddy; but, at the same time, it caused more water loss by percolation throughthe cracks developed during the period of mid-term drainage. The bundssurrounding the fields were lined with clay soil, and this was found to behelpful in reducing the border percolation losses. Crop coefficients weredetermined for both the varieties with available local climatic data, and it wasfound that these values differed greatly from the earlier recommended valuesfor use.However, it was felt necessay to conduct more experiments in order todetermine crop coefficient values with higher accuracy.

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Simple interception ditches were applied in this study withthe objective of determining their effect on soil loss and runoff water. Soil lossand its relationship to changes in the soil surface were investigated with bucketand surface level techniques.Experimental results were discussed based onthe data for rainfall characteristics and soil physical properties. Emphasiswas given to clarifying the product of rainfall kinetic energy and maximum 30-min rainfall intensity (EI₃₀) in relation to soil loss.

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Many small-scale on-farm water development projectsdepend on groundwater and low-level surface water for their water resources;water lifting is indispensable for taking advantage of these resources.Whilethere is a tendency to replace some of the traditional devices with modern pumpequipment, there is a need to promote traditional means of liftiug water byhuman, animal, wind, and water power.The paper introduces water liftingtechnologies which have been developed and are being used in China usingrenewable energy, with emphasis on the water turbine pump.Technical characteristicsand installation/operation of the pump as well as points for futureconsideration are also discussed.

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From a number of studies on groundwater availabilitycarried out in the past, three major studies have been reviewed. These studiespresent conflicting and widely varying assessments of groundwater availability. Estimates of future groundwater development potential vary from 5, 500 to 17, 900 million m³ (MCM). The main reasons for these widely varyingassessments are differences in conceptualization of the physical process, differentmethodologies developed for assessment and use of different data bases.
Of the three studies, the conceptual basis of the annual recharge modeldeveloped by the Master Plan Organization (MPO) is the most appropriate. However, reservations have been expressed in many quarters about the assessmentsmade by MPO, mainly questioning the input data. Their findings can, however, be taken as an indicator of the future potential. The envisagedgroundwater resources to be developed by the and of the Third Five Year Planin 1990 are to use about 35% of the future groundwater development potentialestimated by MPO. Although the plan is ambitious, it would be prudent not toaim for such massive groundwater development in view of the present status ofthe data base.
Review of groundwater quality data has shown that the naturally occurringchemicals in the water are well within acceptable limits and that the groundwateris in general of good quality. The current uses of agricultural fertilizerand pesticides are stills too low to affect the water quality.

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