Estimation of annual evaporation losses for the Makhoul Dam reservoir (under construction)

Abstract

The Evaporation problem is considered one of the most important problems that dam reservoirs suffer from because of the economic losses and costs of treating. Makhoul Dam, which is a dam under construction in Iraq. In this research, a study was conducted to estimate the evaporation losses from the dam’s reservoir. The type A pan was used to measure daily evaporation for a full year, starting from July 2022 until June 2023. The GES program was used to estimate the shape of the reservoir based on Based on the information available for the dam and DEM satellite images of the area with a resolution of 30 meters. Two sites were chosen to measure evaporation, one in the city of Al-Zab, approximately in the center of the reservoir, and the other in the village of Tal Ali, about 30 km from the dam. The results showed that the cumulative total of annual evaporation from the Al-Zab measuring station reached 1547 mm/year, and the cumulative total of annual evaporation from Tal Ali station reached 1766 mm/year. The evaporation rate from the two stations was taken to calculate the annual rate of evaporation from the reservoir, which amounted to 1656 mm/year. Two hypotheses were imposed for the method of evaporation from the reservoir. The first assumed that the reservoir was full throughout the year. In this case, the evaporation losses from the reservoir would be 380,631,600 cubic meters/year, or the equivalent of 15% of the volume of the storage. As for the second hypothesis, it assumed that the reservoir is variable throughout the year, starting with the highest level in the spring and then decreasing. Gradually until the end of autumn, then it increases again in winter. In this hypothesis, the annual losses will be 288,175,555 cubic meters / year, or the equivalent of 11% of the volume of the storage