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EFFECTS OF WATERSHED RESTORATION ON WATER QUALITY AND QUANTITY OF KAPTAI LAKE IN BANGLADESH

EFFECTS OF WATERSHED RESTORATION ON WATER QUALITY AND QUANTITY OF KAPTAI LAKE IN BANGLADESH. Laskar Muqsudur Rahman, PhD Conservator of Forests FOREST DEPARTMENT , BANGLADESH. Forest types of Bangladesh. Forest Types of Bangladesh. Unclassified State Forests 5.08%. Hill Forests 4.65%.

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EFFECTS OF WATERSHED RESTORATION ON WATER QUALITY AND QUANTITY OF KAPTAI LAKE IN BANGLADESH

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  1. EFFECTS OF WATERSHED RESTORATION ON WATER QUALITY AND QUANTITY OF KAPTAI LAKE IN BANGLADESH Laskar Muqsudur Rahman, PhD Conservator of Forests FOREST DEPARTMENT , BANGLADESH

  2. Forest types of Bangladesh

  3. Forest Types of Bangladesh Unclassified State Forests 5.08% Hill Forests 4.65%

  4. Forest Types of Bangladesh Coastal afforestation 1.24% (Mangrove) Mangrove Forests 4.09%

  5. Forest Types of Bangladesh Sal Forests 0.83% (Shorea robusta) Village Forests 1.83% ?

  6. Forest Types of Bangladesh SOCIAL FORESTRY (IN MARGINAL LANDS) Block Plantation Agroforestry Embankment Plantation Railway Plantation Roadside Plantation

  7. Forest Types of Bangladesh Rubber plantation Bamboo groves Tea garden

  8. River Network of Bangladesh

  9. River Network of Bangladesh Bangladesh is a riverine country . About 800 rivers including tributaries flow through the country constituting a waterway of total length around 24,140 km

  10. Transboundary Rivers Total Rivers 57 With India 54 With Myanmar 3

  11. Wetlands of Bangladesh Total area of wetlands  throughout  Bangladesh exceeds 8 million ha. i.e., about 50% of the total national land. Less than 10% of the total water flow originates from country’s own catchments and rest comes from India, Nepal and Bhutan.

  12. River Karnaphuli is the principal river of CHT & Chittagong oiginating from the Lushai hills in Mizoram State of India, flows 270 km southwest through Rangamati to empty into the Bay of Bengal, through Port City Chittagong.

  13. The dam has a 745 feet (227 m) long spillway containing 16 gates. Through the spillway 5,250,000 cu ft/s (149,000 m3/s) of water can pass. The dam has a 745 feet (227 m) long spillway containing 16 gates. Through the spillway 5,250,000 cu ft/s (149,000 m3/s) of water can pass. The dam has a 745 feet (227 m) long spillway containing 16 gates. Through the spillway 5,250,000 cu ft/s (149,000 m3/s) of water can pass. The dam has a 745 feet (227 m) long spillway containing 16 gates. Through the spillway 5,250,000 cu ft/s (149,000 m3/s) of water can pass. The dam has a 745 feet (227 m) long spillway containing 16 gates. Through the spillway 5,250,000 cu ft/s (149,000 m3/s) of water can pass. The dam has a 745 feet (227 m) long spillway containing 16 gates. Through the spillway 5,250,000 cu ft/s (149,000 m3/s) of water can pass. The dam has a 745 feet (227 m) long spillway containing 16 gates. Through the spillway 5,250,000 cu ft/s (149,000 m3/s) of water can pass. The dam has a 745 feet (227 m) long spillway containing 16 gates. Through the spillway 5,250,000 cu ft/s (149,000 m3/s) of water can pass. The Kaptai Lake The Karnaphuli River, was dammed in 1962 primarily for development of hydroelectric power, flooding an area of about 68,000 ha, to become the Kaptai Lake. It is the largest man-made freshwater lake in Bangladesh.

  14. The dam has a 745 feet (227 m) long spillway containing 16 gates. Through the spillway 5,250,000 cu ft/s (149,000 m3/s) of water can pass. The dam has a 745 feet (227 m) long spillway containing 16 gates. Through the spillway 5,250,000 cu ft/s (149,000 m3/s) of water can pass. The dam has a 745 feet (227 m) long spillway containing 16 gates. Through the spillway 5,250,000 cu ft/s (149,000 m3/s) of water can pass. The dam has a 745 feet (227 m) long spillway containing 16 gates. Through the spillway 5,250,000 cu ft/s (149,000 m3/s) of water can pass. The dam has a 745 feet (227 m) long spillway containing 16 gates. Through the spillway 5,250,000 cu ft/s (149,000 m3/s) of water can pass. The dam has a 745 feet (227 m) long spillway containing 16 gates. Through the spillway 5,250,000 cu ft/s (149,000 m3/s) of water can pass. The dam has a 745 feet (227 m) long spillway containing 16 gates. Through the spillway 5,250,000 cu ft/s (149,000 m3/s) of water can pass. The dam has a 745 feet (227 m) long spillway containing 16 gates. Through the spillway 5,250,000 cu ft/s (149,000 m3/s) of water can pass. The Kaptai Lake • The lower part of the Kassalong River, • major tributary of the river Karnaphuli, • has formed the lake. • The lake is “H” shaped, bearing two • arms, joined by a narrow gorge. • The Karnaphuli, Kassalong & Myani Rivers • feed the right arm and • The Chengri and the Rainkhiong Rivers • feed the left arm.

  15. The dam has a 745 feet (227 m) long spillway containing 16 gates. Through the spillway 5,250,000 cu ft/s (149,000 m3/s) of water can pass. The dam has a 745 feet (227 m) long spillway containing 16 gates. Through the spillway 5,250,000 cu ft/s (149,000 m3/s) of water can pass. The dam has a 745 feet (227 m) long spillway containing 16 gates. Through the spillway 5,250,000 cu ft/s (149,000 m3/s) of water can pass. The dam has a 745 feet (227 m) long spillway containing 16 gates. Through the spillway 5,250,000 cu ft/s (149,000 m3/s) of water can pass. The dam has a 745 feet (227 m) long spillway containing 16 gates. Through the spillway 5,250,000 cu ft/s (149,000 m3/s) of water can pass. The dam has a 745 feet (227 m) long spillway containing 16 gates. Through the spillway 5,250,000 cu ft/s (149,000 m3/s) of water can pass. The dam has a 745 feet (227 m) long spillway containing 16 gates. Through the spillway 5,250,000 cu ft/s (149,000 m3/s) of water can pass. The dam has a 745 feet (227 m) long spillway containing 16 gates. Through the spillway 5,250,000 cu ft/s (149,000 m3/s) of water can pass. The Kaptai Lake Watershed Unclassified State Forests (USF) & Other land use is roughly double of the Forested Watershed area

  16. Topography, Soil & Climate • Most parts of this watershed are • mountainous with some up to 2438 m MSL. • The beautiful landscape • is comprised of semi-consolidated and • consolidated rocks, possessing steep slope • of elevation ranging from 350 to 1 000 m • above MSL. • The soils are mainly acrisols in the hills and • lixisols in the valleys.

  17. Climate Source:

  18. Multipurpose Kaptai Lake Requirement of water level: • 27.07 m MSL is required • for safe operation of the power plant . • below 24.38 m MSL the generation of hydro • electricity power disrupted. • When the water level falls below 22.25 m MSL • the generation of hydro-electricity is ceased at • all five units of the 230-MW plant.

  19. Multipurpose Kaptai Lake It also plays a vital role for - Navigation Agriculture Sports Fishery Recreation Control deadly floods due to torrential monsoon rain

  20. Shifting cultivation: Threats to Kaptai Lake • Shifting cultivation reduced the natural system of soil conservation. • 60,000 families use 85,000 ha of the hill forests • Soil loss 26–68 t ha-1 yr-1

  21. Deforestation: Threats to Kaptai Lake Except the Kassalong RF and Rankhiang RF, the almost entire watershed area of the lake has been deforested. As a result, the hill lands are mostly covered with scrubs which include scattered trees of different species, bamboos, grasses and shrubs. For this reason, soil cover has been exposed and rainwater easily causes soil erosion, severe run-off and landslides during monsoon.

  22. Human settlement: Threats to Kaptai Lake

  23. Growing agriculture: Threats to Kaptai Lake Population pressure increased in the vicinity of the Kaptai Lake for swallowing most of the best valley-bottom land for cultivation. Unscientific cultivation causes soil erosion.

  24. Massive teak plantation: Threats to Kaptai Lake Besides, there are concerns that teak plantations cause excessive erosion and soil depletion.

  25. RESTORATION & REHIBILITATION FD initiated in 1980s a rehabilitation programme for Jhumias

  26. RESTORATION & REHIBILITATION Between 1990 and 2010 about 33000 ha of forest plantations were raised.

  27. RESTORATION & REHIBILITATION • 2300 shifting cultivator families have been settled. • Another 6,500 households were rehabilitated by the Chittagong Hill • Tracts Development Board. • Each family allotted 2 ha land for housing & horticulture, also cash • capital for Alternate Income Generation.

  28. RESTORATION & REHIBILITATION The projects have provided alternatives to jhum cultivation, particularly home gardening since the 1980s.

  29. MATERIAL AND METHODS Sampling sites FOUR sampling stations were selected :

  30. MATERIAL AND METHODS Sampling Water samples were collected from 0.2D and 0.8D of the cross-section at three equal distance points using water samplers (DoF, Bangladesh).

  31. MATERIAL AND METHODS • Physicochemical analysis of water samples • Water samples were analyzed to obtain readings on following physicochemical properties of lake water : • pH (TOA pH Meter) • TSS (filtering, drying & weighing method) • Turbidity (Geopack Digital Turbidity Meter) • DO (measured by Jenway 970 DO2 Meter) • BOD5 (difference between initial DO and 5 day DO measured by DO2 Meter), and • Velocity (was measured by Geopack Digital Velocity Meter)

  32. Results

  33. pH pH ranged from 5.3-6.2 and 5.1-6.1 in station A and station B, respectively with low pH value in station B during wet season. Although these small changes in pH are not likely to have any direct impact on aquatic life, they greatly influence the availability and solubility of all chemical forms in the lake and may aggravate nutrient problems.

  34. Total Suspended Solids (TSS) TSS ranged from 121.1 to 1358.4 mg/L and 126.3 to 1793.2 mg/L in station A and station B, respectively with higher quantity of TSS in station B during wet season.

  35. Turbidity Turbidity ranged from 123.1 to 745.3 NTU and 145.5 to 825.8 NTU in station A and station B, respectively with higher turbidity in station B during wet season.

  36. Dissolved oxygen (DO) DO varied between 6.0 mg/L to 7.3 mg/L and 5.1 mg/L to 6.9 mg/L in station A and station B, respectively with lower DO in station B throughout the year except during rainy period.

  37. Biological Oxygen Demand (BOD5) • It varied between 5.1 mg/L to 8.3 mg/L and 5.7 mg/L to 10.2 mg/L in • station A and station B, respectively with higher BOD in station B • throughout the year. • During wet season BOD was comparatively higher in both the • stations.

  38. Velocity of stream flow Velocity of stream flow is slightly low (0.04 m/s) at B cross-section during dry season as compared to that from A cross-section. (0.05 m/s) Conversely, it is high during wet season at B cross-section (0.63 m/s). Similar variation in velocity was observed in the cross-section of main channel C (1.16 to 2.89 m/s) and D (1.08 to 3.32 m/s).

  39. DISCUSSIONS Excessive TSS and higher turbidity where the lake-bank was devoid of vegetation and under shifting cultivation indicates high rate of siltation to shorten the life-time of the lake. The situation is further aggravated during the monsoon. On the other hand the lake passing through its watershed with forest plantations and controlled shifting cultivation exhibited comparatively better physicochemical properties The results indicates that tree cover retards run-off and soil erosion and help maintain water quality and influence stream flow. Further in-depth study will generate data to help impress policymaker to bring the watersheds of Kaptai Lake under forest plantation programmes, control of shifting cultivation and adoption of policy for environmentally sustainabale agriculture.

  40. CONCLUSIONS Massive tree restoration programmes in the vital watersheds, and forestry practices should be planned in such a way that the forest production, and water yield and quality are in complete harmony.

  41. ACKNOWLEDGEMENTS Forestry Development & Training Centre, Kaptai Pulpwood Forest Division, Kaptai Karnaphuli Hydro Power Station Authority, Kaptai Bangladesh Water Development Board Bangladesh Department of Fishery

  42. THANK YOU

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