Flood Routing of Tigris River in Baiji Station and Makhoul Dam Reservoir under Supposed Operation of the Dam

Abstract

The digital elevation models (DEM) used for geometric analysis of the reservoir, as essential requirement  in the study of flood routing in the reservoir and in Baiji station on Tigris river, the volume of storage, volume of island, positive and negative planner area and surface areas, residual capacity, reservoir average depth, and average thickness of the island, were estimated, at each hypothetical level from 108-160 meters above sea level, the geometric elements of storage volume and residual capacity are used directly for flood routing.

The assumptions that have been assumed as basis for flood routing methodologies are:

• The input discharges to Baiji station before assuming the existence of the dam is the same input discharges in the reservoir after the assumption of existence and operating of the dam.
• The input discharge in Baiji station after construction of the dam is the same output discharge from gates.
• The presence of initial reserve before the arrival of flood wave, as the reservoir is not empty before the flood.
• Neglecting the drawn amount of water between the dam and Baiji station for irrigation and industrial purposes because of their small value.
• The outflow from the gates was assumed for each operating scenario, the water level should not reach the critical one in the reservoir and Baiji  gaging station.
• If the river discharge in Baiji station not reach the destructive (critical) level, means that the level not reach the critical level in the other stations in downstream (Tikrit, Samarra, ... etc.).

Two mathematical models were used for flood routing purpose, the first is a relationship of discharge-level to predict the level in Baiji station depended on outflow from gates, and the second is the relationship of storage-level to predict the level in the reservoir depended on storage volume when the leave of the flood wave, an algorithm and flow chart were developed to describe and explain the steps of the flood routing program, which can be modified and applied for any dam reservoir in the world, and it is used in current study, also to calculate inflow discharges then inflow volumes, either outflow discharges may assumed for eleven operating scenarios (at 11 supposed levels to receive the flood wave) and predict the equivalent level in Baiji, and the change in storage, and then the accumulated volume and the equivalent level in reservoir, when the end of flood wave.

The optimum levels in the reservoir as well as in Baiji station depends on outflow discharge from the reservoir outlets, the predicted levels ranged between (103.83-105.75) meters above sea level in the station, resulting by outflow from the gates ranged from (1000-4500) m³/sec for each supposed scenario, knowing that these outflows within the discharge capacity of gates.

So, the routing reveal to not get flood in Baiji because the levels are not arrival to the critical case, and the results confirm the non-arrivals of the level in the reservoir to a critical situation, according to these scenarios the water level ranging between (150.53-151.90) meters above sea level, and the equivalent storage volumes ranging from (4252686180-4518813396) m³ in the reservoir, in condition of the dam operator apply the current supposed operation system.