National Hydrology committee of Afghanistan (NHCA) Sedimentation in Reservoire

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1 National Hydrology committee of Afghanistan (NHCA) Sedimentation in Reservoire OCt.2007 Prof. Mohammad Qasem Seddeqy KPU

2 بسم االله الرحمن الرحيم وجعلنامن الماءکل شي ء حی 30 واز ا ب هر چيزی رازنده گردانيدیم سوره انبيا ایه

9 Classification of Rivers according to the topography of the river basin Upper reaches in the hilly region Lower reaches in the alluvial plain Rivers on alluvial plains may be broadly classified in to three types: 1. The meandering type 2. The aggrading type 3. The degrading type

11 Sediment is fragmental material, primarily formed by the physical and chemical disintegration of rocks from the earth crust. The process of moving and removing from their original source or resting place is called erosion

12 Why a good understanding of sediment transport processes is indispensable 1. Morphological boundary condition for design of Hydraulic structure and river training works 2. Sedimentation in reservoirs 3. Sediment problems at Intakes 4. Environmental Impact assessment

13 Origin and types of Sediment Cohesive Non Cohesive Cohesive sediment the physical- chemical interaction between particles plays a significant role. Non Cohesive sediment there is no physical and chemical interaction between individual particles.

15 Sediment Control Plan Q Control Point (Q+A-B)*α B A E C D Target Area E=(Q+A - B)(1 -α) - C - D

16 Sediment Control Plan E=(Q+A - B)(1 -α) - C - D E : Design allowable sediment discharge Q : Design sediment discharge at the design control point of the upstream end of the subject sub-basin basin A : Design sediment production B : Design reduction of sediment production α : Ratio of volume of channel sediment mitigation C : Design reduction of sediment discharge D : Design mitigation volume of sediment discharge

17 Sediment Control Dam Function 1: To Stabilize Hillside Slopes Scouring force becomes less than before; Shallower in depth, Slower in velocity

18 Sediment Control Dam Function 1 To Reduce Sediment Discharge Sediment Capacity for Flood Period Initial Sediment Capacity

19 Sediment Control Dam Function 2: To Mitigate Streambed Erosion by milder bed-slope with Stepwise Dams L h m n 1 1 m>n L=((m*n)/(m - n))*h

20 Sediment Control Dam Function 3: To Mitigate Sediment Runoff Design Sedimentation Line to Cover the Unstable Sediment Deposition Unstable Sediment Deposition

24 3D VIEW OF KABUL RIVER BASIN Kabul Naghlu dam Oulet basin

25 3D View of Alingar River Basin Darunta Dam

26 Other view from agriculture land of Gulbahar Panjsheer desert

27 3D view of Sorobi and Naglu dams Naghlu dam Sorobi dam

28 3D View of from Kunar River Kunar river Pakistan Darunta dam

29 3D View of Darunta Dam Darunta dam : Date Landsat 7 satalite 22

30 3D View of Panjsheer river Basin Gulbahar desert Naghlu dam Darunta dam

31 Darunta Reservoir 24 years ago : Date Landsat 3 satalite 20

40 Sedimentation Intensive soil erosion has been causing rapid sedimentation of reservoirs with an important loss of irrigation lands, power generation capacity and life time of reservoirs Afganistan is facing annually with 150 million m3 sedimentation in the reservoirs and 400 million m3 sedimentation to downstream of dam reservoirs and irrigation networks

41 Causes of sedimentation Desertification 1. Continued deforestation from logging and fuel wood needs : In South,east and northeast of Afghanistan. 2. overgrazing:the grazing lands used by Kochis (nomads)have been dried out due to the lack of sufficient rainfalls & converting to cultivable land causing considerable reduction in livestock and livelihood. 3. Destroying land covers bush used for fuel wood 4. Soil erosion due to flood and wind 5. Unsustainable agriculture :Salinization: of soil,over use of agricultural inputs. 6. Drought :Started in 1969,getting up to a critical status in ,causing hydrological circulations of the soil

42 Lack of river mangement and training work Land use steep drainage basin slopes and relief high rainfall magnitudes and frequencies Lack of Reservoir maintenance

43 Extensive destruction of forest over the past 25 years

44 Sedimentation and erosion problems affect the following sectors. Health(drinking water, domestic ) Society Economy(Water supply,irrigation,hydropower,maintenance and operation of Reservoir,Navigation Navigation,Flood Protection,Fishery ) Environment

45 Flash flooding is a direct consequence of land cover degradation in Balkh river 26 March, 2003

46 Sediment deposition into reservoirs has several major detrimental effects. Loss of storage capacity. Damage to or impairment of hydro equipment. Bank erosion and instabilities. Downstream channel modification. Reduced downstream suspended sediment load. Upstream aggradations. Effect on water quality. Effect on waste assimilation. Effect on navigation and recreation. Effect on aquatic life.

47 Plans for mitigation of erosion and sedimentation For urgently Dredging, Sub cut, empty washing Reforestation and plantation for land covering long term Preparation of National Strategy and policy for erosion and sediment mitigation. Use water resource potential in the country through rain and flood water harvesting, construction of small, medium, and large depressions, pools and dams for flood control and prevention of erosion. Construction of protective structures along river where sliding may occur.

48 Immediate Response Good river management :includes sediment and floodplain management National Emergency Employment Program, National Solidarity Program and National Hydrology program of Afghanistan (NHCA), Based Development program and other Nationwide programs are contributing to Erosion and sedimentation relief Emergency Rehabilitation Irrigation Project (Hydraulic structures) Intermittent meetings by UN and Governmental and well-known non-governmental Agencies for assessing response and coordination regarding erosion and sedimentation management and capacity Building

50 conclusion The principal reservoirs of Afghanistan are rapidly losing their storage capacity and day by day exacerbated because of high rates of sediment influx and accumulation. The factors that promote sedimentation in the reservoirs include land use, steep drainage basin slopes and relief, and most importantly, high rainfall magnitudes and frequencies and lack of o maintenance due to prolong war. connecting reservoirs at high elevations with those at lower elevations, results in an increased drainage area and available water. As the upstream reservoirs fill with sediment, however, the bottoms reach the outlet structures and sediment is bypassed into the lower reservoirs, accelerating the sedimentation rates in these impoundments.

51 Reservoirs with small drainage areas loss storage capacity at a faster rate than reservoirs with larger basins, especially in developed basins. In reservoirs with large basins however,intense rainfall in a short period can transport large amounts of sediment into the reservoirs, rapidly depleting their storage capacity.

52 Efforts to significantly increase the overall water resources by simply building more dams over time, is proving to be ineffective on a long-term basis.

53 Thank you for attention

Stream Geomorphology. Leslie A. Morrissey UVM July 25, 2012

Stream Geomorphology. Leslie A. Morrissey UVM July 25, 2012 Stream Geomorphology Leslie A. Morrissey UVM July 25, 2012 What Functions do Healthy Streams Provide? Flood mitigation Water supply Water quality Sediment storage and transport Habitat Recreation Transportation