The use of digital elevation model and GIS for geometric analysis of water reservoir to feed the hypothetical irrigation project west Makhoul in Salahuddin province

Abstract

The reservoir under study is one of the basic components of the supposedly irrigation project, the geometric analysis of the reservoir was conducted, the geometric elements were extracted from the DEM, which are represented by the positive volume (the volume of islands), negative volume (volume of water storage), positive planner area (the projections of islands), negative planner area (area of evaporation), positive surface area (undulated surface of islands), negative surface area (bottom wetted area), average thickness of islands and the average of depth, at selected levels of the reservoir, the relations between geometric elements and water level, and geometric elements with each other, reveal that the positive volume and positive areas typically fluctuated with the changes of water level, because the immersion of islands and emergence of new other islands with the rising of levels, these elements are important for the future uses for these positive areas, as well as in the future maintain within the reservoir, and the way of movement between parts, and possible problems due to landslides from the positive parts towards the negative ones.

The negative volume and negative areas are very important in the operational policy of the reservoir, which are a positive not fluctuated relationships, the negative volume, negative planar and surface areas increased with the beginning of the level rising as low sharpness, then the sharpness of these relationships increased because of the relatively large increase of these elements after the departure of reserve from the original stream of Al-Jafr valley to its shoulders.

The study also showed that the topography of the bottom and the islands are not significantly complicated, that facilitating the use of the area for tourism purposes and the construction of other parts of the irrigation project.

According to the derived geometric elements from the digital elevation model, mathematical model were developed for predicting the water levels which are achieved inside the reservoir in terms of water volume that is pumped into the reservoir, that have great significance in the operational program for the project.

The study reflect that the supposed reservoir may contain twirled reserve of water enough for up to 20 days of continuous pumping to the main channel with average pumping 50 m³/s, the operator can control the volume of storage by the operational program which is subject to the variation of demand in the main and secondary channels.