Determination of the best temperature based method of evaporation estimation from the Karde reservoir in order to investigate the effect of reducing useful volume of the reservoir on evaporation from the lake surface

Nowadays water scarcity has become one of the most important problems in many communities. Construction of dams and water storage to provide part of the required water and flood control is one of the ways to coexist with problems caused by Water scarcity, flood or drought. Evaporation of lakes, reservoirs and ponds surfaces in the optimal utilization of water resources is highly effective. The evaporation of surface waters, usually in dry areas, especially in areas where heat transfer horizontal flow there is significantly will be greater than the wet areas. On the other hand, over time, the rate of sedimentation in the reservoir will increase. One of the problems of sedimentation is changes in the geometry of the reservoir and dam lake level rise to different amounts per storage volume. This in turn leads to increased evaporation due to rising levels of Lake dam. So the main purpose of this research is estimate the rate of evaporation from the lake and choose the most appropriate method for estimating evaporation from the surface of the lake and also determine the effect of sedimentation on evaporating from the surface of the lake of dam. In order to estimate the rate of evaporation from the Kardeh lake, first by using 6 thermal evaporation method such as Jensen-Haise, Hamon, Estefen- Stewart, Papadakis, Abtew and Turc evaporation rate was estimated in monthly, quarterly and annual scale. Then these values were compared with data from pan evaporation, using nine indicators evaluate errors. Also to determine the impact of sedimentation on the evaporation of the lake of this dam, According to the Hydrographs that was conducted in the years 1375-1376, 1382-1383 and 1387-1388, reservoir levels per amount of storage volume (5 scenario includes volumes 5, 10, 15, 20 and 25 million cubic meters) was determined. The results show that Jensen-Haise method, is the best thermal method of estimating evaporation in terms of lack of pan evaporation measured data. . It should be noted that in order to estimate the evaporation in monthly or seasonally scale, Papadakis method for winter and Turc method for the summer season will be appropriate methods. Also by reducing profitable volume due to sedimentation, reservoir lake level (per amount of stored stream) increased. So that this increased level by increasing the storage volume from 5 million cubic meters to 25 million cubic meters, Evaporation rate increase to three times the first case. In other words, it can be stated that with 5 times the volume stored in the reservoir (storage volume change from 5 to 25 million cubic meters) and also increase sedimentation the volume of surface evaporation 3 times increases. . Studies show that all methods whether overestimated or underestimated, show Increased evaporation process by changing the storage volume during the mentioned years due to increase the level of the lake of Kardeh reservoir. Jensen-Haise due to the closest data with pan evaporation data and earn the most points from the total score of 9 evaluation index error in estimating evaporation from between 6 ways, were selected as the best thermal method for estimating evaporation in terms of the lack of pan evaporation measured data in the region. Hamon estimation of evaporation method is the most underestimated and Etefen - Stewart method is the most overestimated method. Increasing sedimentation in the reservoir improve the water level to higher level in the reservoir, due to the openness geometry of the Kardeh reservoir, increasing the level of the lake will follow and ultimately increase the rate of evaporation from the surface of the reservoir.