Management of water resources become one of the most important subjects in the human's life. The water sustains life on earth, therefore; more care for water management is necessary. In the last years, studies show water use will be more in the world as result of rapid increase in population, industrialization, and urbanization etc. The evaporation losses from dam's reservoirs and lagoon form very huge losses in water resources. The annual evaporation depth losses in Iraqi Western Desert is about (2.25 -3) meter, this depth store the highest percentage of the small dams. Sub-surface storage reduces evaporation losses and maintains water quality by minimizing salt concentration. In present study, three tanks are used to simulate the subsurface reservoirs to study the effectiveness of underground storage on reducing the evaporation loss. Each tank have squares cross section tanks of (80) cm length and (40) cm depth and filled up to (34) cm with different graded soil (labeled as A, B with coarse soil, and D with fine soil) to simulate the storage below the ground. While the forth tank filled with water (labeled as C) to represent the reservoir of direct evaporation for comparison study. The present study considers three parameters that can controlled the evaporation from subsurface reservoirs: (a) temperature variation, (b) water table variation, and (c) material properties such as porosity. The field study continues for four months, it was started at Jun.11, 2016 and ended at Dec. 15, 2016 in the Erbil city at north of Iraq. The results showed evaporation losses are reduced by using subsurface storage reservoir with gravel in comparison with free surface evaporation. The evaporation losses are reduced about 46 % , 39% , 64% when the water table below gravel surface range from 5 to 10 cm , while at 20 cm depth of the water table the evaporation reduction is about (85 % to 86% 95%) from A, B and D tanks with porosity 0.65 ,0.67 and o.35 for A ,B and D tanks, respectively..
minimizing the surface area of a reservoir during maximum evaporation losses period. A mathe-matical relationship linking the depth of water with the surface area of the reservoir has been formulated, and its integration can be used to estimate conservable water quantities. Reducing the water level in the reservoir to the minimum permissible level before the dry months has re-duced the evaporation losses by 65% and 51% for the two scenarios. These two scenarios have been conducted by assuming that the dry months start with the presence of the water level in the reservoir at a height of 14 and 12 m, respectively. On the other hand, evaporation losses during drought months have been decreased by 24%. By this technique, it can be possible to obtain wide areas suitable for agriculture, contributing to the economic and social development of the region. Also, Depth index(DI) suggested in this study and defined as the ratio of volume of the water in the reservoir to corresponding surface area, to compare the location of the best dam among the 13 proposed dams in Wadi Houran by reducing evaporation losses. The results of this index showed the best location was at DI=10.901 in DM 7, and the worst is at DI=2.425 in DM 8.
In this paper the artificial neural network used to predict dilly evaporation. The model was trained in MATLAB with five inputs. The inputs are Min. Temperature, Max. Temperature, average temperature, wind speed and humidity. The data collected from Alramadi meteorological station for one year. The transfer function models are sigmoid and tangent sigmoid in hidden and output layer, it is the most commonly used nonlinear activation function. The best numbers of neurons used in this paper was three nodes. The results concludes, that the artificial neural network is a good technique for predicting daily evaporation, the empirical equation can be used to compute daily evaporation (Eq.6) with regression more than 96% for all (training, validation and testing) as well as, in this model that the Max. Temperature is a most influence factor in evaporation with importance ratio equal to (30%) then humidity (26%).
The aim of this paper is to in investigate the performance characteristics of counter flow wet cooling towers experimentally by varying air and water temperatures, fins angle, rate of air flow, rate of water flow as well as the evaporation heat transfer, along the height of the tower. The analysis of the theoretical results revealed before that the thermal performance of the cooling tower is sensitive to the degree of saturation of inlet air. Hence, the cooling capacity of the cooling tower increases with decreasing inlet air temperature whereas the overall water temperature fall is curtailed with increasing water to air mass ratio. From the experimental study the efficiency of the cooling tower and cooling tower characteristics are higher in case of low mass flow ratio due to higher contact area of water to air. Because of better contact area between airs to water the drop in performance of the cooling tower is less. The effect of fins angle on the thermal performance of counter flow wet cooling tower was predicted. The experimental study showed that the cooling range, cooling coefficient, , heat load , change in air relative humidity and cooling tower effectiveness increased with increasing fins angles and optimum fins angle obtained from this experimental work was 70 degree, at this angle all cooling tower performance has been calculated were better. While the approach increased with decreasing fins angles, the minimum approach was obtained for 70 degree fins angles and the maximum approach was obtained for 30 degree fins angles.
The studying of the distribution of wetting patterns in soils having a stratified profile is of great importance due to the presence of this type of profile in abundance in agricultural lands, including greenhouses. Therefore, there was a need to develop a numerical program that predicts the dimensions of the wet area of the subsurface drip irrigation system under different operating conditions for purpose design and manage these systems properly to avoid water losses resulting from evaporation or deep penetration. The present study aims to develop a two-dimension model simulates the wetting pattern in stratified soils using (HYDRUS-2D) software and study the effect of soil hydraulic properties and different operating conditions on the progress of the wetness pattern and the interference pattern between two wetting fronts. Laboratory experiments were carried out for the system of subsurface drip irrigation in stratified soils that consisted of three layers (silty clay loam soil, loamy sand soil, and sand soil) arranged from bottom to up. Three different emitter flow rates 0.5, 1, and 2 l/h were tested, as well as three different initial moisture contents for each soil layer were considered. The interference pattern between two wetting fronts of two emitters with different spacing between emitters 30, 40, and 50 cm was studied. A numerical model was developed to guess the horizontal and vertical dimensions of the wetting zone for the single emitter and the pattern of interference between the two wetting fronts of two emitters. The predicted values obtained from the numerical model were compared with those obtained from laboratory experiments. Statistical analysis of the obtained data showed that the developed numerical model has a good ability to guess the dimensions of the wet pattern of the single and the two emitters and there were good agreements between the predicted and the experiments results and minimum values of RMSE ranged between 0. 5 and 3.6 were achieved.