Engineering and Technology Journal

AL-Sulaymania city is located in the northeast of Iraq at an altitude of 845 m from the sea levelbetween longitudes (44 30 00 – 46 20 00) east and latitudes (34 33 00- 36 30 00) north. It covers an area of approximately 20000 km². The study area includes several geological formations (from the oldest to the earliest), Balambo Formation (Early Cretaceous), Qumchuqa, Kometan, Shiranish, Tanjero, Kolosh, Sinjar Formation and Quaternary deposits. The climatic data recorded by AL-Sulaymania meteorological station for the period (1980-2016) shows that the total falling rain was (423.86) mm, the temperature was (13.88 ° C), relative humidity was (22.36%), wind speed was (2.08m / s), sunshine was (8.06  hours / day), and the total evaporation from free surfaces was (1747.4mm). The climate of the study area is wet in winter and dry in summer.Corrected potentialevapotranspiration was calculatedtheoretically byapplying Thornthwaite method, where the value was 589.02mm, the water surplus was also calculated, which accounted for 74.24% divided  into surface runoffand its value was 41.02 mmand GroundwaterRecharge which was 92.65mm,whilethewater deficit represents25.76 % of theannualrainfall.

Erbil city located, in the northern part of Iraq, within the central basin of Erbil plain which covers an area about 1400 Km2 where Erbil city area measures about 70 Km2, is located between latitudes (36ᵒ 08 30̋ - 36ᵒ 14 15̋) north and longitudes (43 ° 57 '30 "- 44 ° 03' 20") east, The rocks exposures at the central Erbil plain date back to the (Upper Miocene-Recent) and this includes Ingana, Muqdadiya, Bai Hassan formations as well as Quaternary deposits. Tectonically, the studied area is located within Chumchamal-Butma Subzone at the area of the foothills. The movement of the groundwater in the study area is from the east to the west. Depending on the climatic data recorded in Erbil station for the period (1980-2016) shows that the total falling rain was (418.0) mm, and the temperature (15.81 ° C), relative humidity (29.96%), wind speed (1.94 m / s), solar brightness (8.28 hours / day) and the total evaporation from free surfaces was (1674.8 mm) the prevailing climate in the region is moist-humid to moist. corrected potential evapotranspiration was calculated theoretically apply Thornthwaite method where she was value 734.58 mm, was also calculate the water surplus , which accounted for 79.18% divided into surface runoff and its value 39.36 mm and Groundwater Recharge 87.82 while the water deficit represents 20.82% of the annual rainfall as the annual recharge rate was calculated for Erbil Central Basin and is reached 122.94 × 106 m3/year.

The objectives of the study are to predict the crop coefficient for Maize using watermarks gypsum blocks and atmometer apparatus during the growing stages, 2013, compare the estimating values with Food and Agriculture Organization in United Nations (FAO) and local study work. Thestudy work was conducted in the Al-Yusufiya field Township, 30km south of Baghdad under semi- arid weather conditions. The watermarks and atmometer were used to measure crop evapotranspiration and reference evapotranspiration, respectively. The predicted average value of crop coefficient for initial, develop, mid and late of seasons were: 0.14, 0.6, 0.91 and 0.57, respectively. The results from the comparison between the estimating crop coefficient and FAO values showed that the average values of relative error was36.29%and with mean absolute error was0.27. Moreover, root mean square difference was0.32.Additionallythe comparison between the estimating crop coefficientswith the local study values showedthat the average values of relative error was33.57% and with mean absolute error was 0.24. Moreover, the root mean square differencewas 0.29.

The variation in climatic conditions of the regions complicates the process of estimating evapotranspiration using one equation or one way because it needs so much data. The adoption of special method for each region based on the lowest climatic parameters and the historical record can be more useful. Five evapotranspiration (ET_0) models had been analyzed statistically by comparing Penman-FAO-24 (PF) model with: Penman Monteith -FAO-56 model (PM), Penman-Kimberly model (PK), Jensen-Haise model (JH) and Hargreaves model (H). The performances of the simpler models were evaluated using bias, root mean square error and Pearson Correlation Coefficient. Also, Regression analysis for predicting (ET_0) from minimum climatic data (Hargreaves model) has been developed. The results indicated that the models which depends on more climatic data are close from each other and that is very clear in (PF), (PM) and (PK). The differences between models are due to wind function used in each model. The developed linear regression model from minimum climatic data (H) model with slope of 1.254, an interception point of -1.801 and coefficients of determination R^2 of 0.988 matched very closely to (PF) model values.