Determination of Difference Amount in Reference Evapotranspiration between Urban and Suburban Quarters in Karbala City

Evapotranspiration represents one of the main parameters in the hydrological cycle. It is usually expressed by the term reference evapotranspiration (ETo) that is affected by certain meteorological parameters. This study aimed to find the difference amount in ETo between urban and suburban quarters in Karbala city. The study methodology involved selecting once urban area and four suburban quarters. Two methods of determining the reference evapo- transpiration were applied: first, a direct method which measured ETo at selected fields by using a hand-held device, and second, an indirect method using the Penman-Monteith equation. The findings showed that the magnitudes of ETo by the Penman-Monteith equation are higher than the values measured by the direct method for urban and suburban quarters. Moreover, it was found that the absolute percentage of difference in the average amount of ETo between urban and suburban quarters is 13% by using the direct method and 61% by using Penman-Monteith equation. The study conclusion is that suburban area has higher magnitude of ETo than urban quarter by using any of direct method and indirect method (Penman-Monteith equation).