Dukan Dam Reservoir Bed Sediment, Kurdistan Region, Iraq

Abstract

The Dukan Dam Reservoir (DDR) in the Kurdistan Region of Iraq has been studied to determine the characteristics and nature of the reservoir and the deposited sediments on its bottom surface. This study was achieved by doing a field survey and grain size analyses of the collected sediment samples at 32 locations representing the whole reservoir area that had been created when the Lesser Zab River was dammed in 1959. The Dukan Dam, which is a multipurpose concrete arch dam, was built on the Lesser Zab River for controlling its flood during high rainfall seasons, irrigation and power generation. The catchment area is 11,690 km 2. The surface area of the reservoir is 270 square kilometers and the volume is 6.870 × 106 m 3 at normal operation level (El. 511.00 m. a.s.l.). The minimum drawdown level is at elevation 469 m above sea level (a.s.l.). The live storage is 6.14 × 106 m 3 while the remainder is dead storage. The reservoir has a surface area that reaches 270 square kilometers and is composed of two sub-reservoirs connected by a narrow channel that has a length of 5 kilometers. The relatively bigger reservoir is located in the north and has a triangular shape with a surface area approximately 250 square kilometers. The smaller sub-reservoir is located down south where the dam exists and it has irregular rectangular shape. Thirty-two sediment samples were collected from the bottom of Dukan reservoir. The bed of the reservoir is mainly composed of 15% gravel, 14% sand, 48% silt and 23% clay respectively. Most of the sediments are very fine grained, very poorly sorted, strongly coarse skewed and mesokurtic.

Bathymetry and siltation rate for Dokan Reservoir, Iraq

“…), silty sandy clay (10%), sandy gravely silty clay (1.2%) and gravely sandy silty clay (1%; Hassan et al . ).…”

“…Different sediment classes, indicating surface distribution area percentages at bottom of Dokan Reservoir (Hassan et al . ).…”

Sediment flux from Lesser Zab River in Dokan Reservoir: Implications for the sustainability of long‐term water resources in Iraq

“…The pattern of storage reduction in the lower Dokan Reservoir is quite similar to that in the upper reservoir. As a result of sediment delivery from small subvalleys on both sides of the two reservoirs, the distribution of coarse sediment was concentrated on the southern half of the upper reservoir and the whole of the lower reservoir (see Figure ) according to the sieve and hydrometer analysis of 32 samples of bed sediment, those were gathered over the reservoir area (Hassan et al, ). The storage volume at 440 m.a.s.l.…”

“…It should be mentioned however that result of sediment delivery from small subvalleys on both sides of the two reservoirs: the distribution of coarse sediment was concentrated on the southern half of the upper reservoir and the whole of the lower reservoir according to sediment size analysis of 32 samples of bed sediment (Hassan et al, ).…”

Watershed Sediment and Its Effect on Storage Capacity: Case Study of Dokan Dam Reservoir

“…This is the third reservoir to be dealt with in Iraq. The bed of the Dokan Dam reservoir (located in the northeast of Iraq) is surveyed by Hassan et al [24], and this studied the bed sediment using 32-bed samples distributed spatially over the reservoir. The results indicate that the bed sediments of the reservoir are composed of silt (48%), clay (23%), gravel (15%) and sand (14%).…”