Evapotranspiration Estimations Using Climatological Approaches
Punjab is called the land of irrigated agriculture with 85% of its cultivable area under irrigation. This high percentage of area under irrigation reveals that Punjab has exploited a considerable part of its water resources for irrigation purposes. But irrigation practices adopted by farmers of Punjab are generally arbitrary and not necessarily based on actual water needs of a crop. Therefore, proper management of water resources had become a matter of vital concern for increasing crop production further, on one hand, and to prevent the exhaustion of underground water resources, on the other hand. Evapotranspiration (ET) is the best criterion which needs to be estimated on a scientific basis so that the required amount of water can be applied to the crop at the proper time, taking into account the effective rainfall and irrigation application efficiency. One of the methods of ET estimation is lysimetery. However, its immobility and high cost restrict its utility. The evaluation of ET by an empirical method is simple and easy to use. The empirical formulae use standard climatological data as the inputs. However, all the proposed empirical formulae hold good in the respective localities where these methods were developed, and cannot be extended beyond these locations. Therefore, a suitable method for determining ET for Punjab is needed to have a reliable estimate with available meteorological data.