Eco. Env. & Cons. 16 (1) : 2010; pp. (71-75) Copyright@ EM International MCU soft - A decision support system to estimate the monthly consumptive use with minimum meteoro- logical observations A.C. Pandey, Ashok Mishra, S.S. Kumar and B.P. Singh Krishi Vigyan Kendra, East Singhbhum Birsa Agricultural University, Ranchi, Jharkhand ABSTRACT To estimate the monthly consumptive use for a particular crop in a particular region is a cumbersome process and several equations have been developed so far. To calculate the total irrigation water require- ment for a particular crop period requires the information of consumptive use/potential evapo-transpi- ration, crop Coefficient, effective rainfall and the overall expected irrigation efficiency. To ease the calcu- lation of consumptive use with minimum data set to predict several thing, as total water requirement for a particular crop, number of irrigation required, irrigation scheduling, in-situ and ex-situ water conser- vation or harvesting practices or size of structures etc, the Lowry Johnson method has been selected and a small Decision Support System named as MCU.soft has been made in the computer language Visual Basic 6.0. The DSS requires only the mean monthly temperature to get monthly Consumptive use/ Po- tential Evapo-transpiration and to predict water requirement per hectare for any field crop, Crop coeffi- cient, Effective rainfall and Expected overall irrigation efficiency. This DSS has been monitored with several data sets and found theoretically correct and ready to help for the researchers. Key words : Decision support system, Evapotranspiration, Consumptive use, Crop coefficient, Effective rainfall. Introduction Consumptive Use can be defined in English only as the water abstracted which is no longer available for use because it has evaporated, transpired, been in- corporated into products and crops, or consumed by man or livestock or Water losses due to leakages during the transport of water between the point or points of abstraction and the point or points of use are excluded. But for the agriculturists it can be de- fined as Consumptive Use is the total evaporation from an area plus the water used directly in build- ing plant tissue. The distinction between the con- sumptive use and evapotranspiration is largely aca- demic, falling well within the error of measurement, and they are now generally treated as synonymous. When used with respect to a specific crop, con- sumptive use is the evapotranspiration experienced if water supply is adequate at all times. Evaporation or vaporization is the process by which water changes from liquid state to vaporous state. This change in state requires an exchange of approxi- mately 2.5 kJ energy for each gram of water evapo- rated. Transpiration is the process by which soil moisture taken up by vegetation is evaporated from the airspaces in plant leaves. Only minute portions of the water absorbed by the root systems of plants remain in the plant tissues; virtually all is dis- charged to the atmosphere as vapour through tran- spiration. The ratio of the water transpired to that used in forming plant matter is 800 or more. The rate of transpiration is largely independent of plant type, provided there is adequate soil water and the sur- face is entirely covered by vegetation. Since photo- Correspondence address : E-mail: acpandey10@hotmail.com