Watershed management, reservoir sedimentation and erosion BByy..XXuuananThQi Quauacchh and Phouvin Phousavanh 1Seite 1
Contents 1. Sediment and Erosion 2. Watershed management 3. Group work 4. Payment for Ecosystems 2
1. Sedimentation and erosion 3
Erosion and sedimentation Types of issues – reservoir sediment accumulation, reservoir and downstream erosion, downstream sediment deposition Influences – land use practices, sediment dynamics, reservoir management and downstream release patterns… 5
1.1. Sediment Risk Assessment Baseline data? Ideally it should include: • Sediment sources and characteristics (e.g. grain sizes) • Land use and vegetation cover • Mapping of sediment production zones • Volume of sand extraction from the river • River morphology • Geology • Hydrological data Reservoir: Design of the monitoring program is important to target hydropower risks 5
1.2. SEDIMENTATION IN A HYDROPOWER RESERVOIR Storage capacity Control gate Pipe to turbine Dam Turbine house Foundation Dead volume Bottom gate Coarse materials Fine materials (Bed load) (Suspension) Bottom gate may release about 10 – 20 % fine materials to down stream only Downstream: “sediment-hungry water” 6
Reservoir Sedimentation: technical hazards • Progressive reduction in dead, and eventually active, storage capacity • When sediment delta reaches dam and intakes, forced slope instability can: • result in temporary blockage of power intakes • cause standing waves in reservoir basin • When sediment is drawn through power inCtaonkterosl gtahteere is an incrSetoarasgeedcarpisackityof abrasion damage to water Pipe to turbine passages and turbines Dam Turbine house Foundation Page 7 7
1.3. Reservoir Sediment Sources? Nurek Reservoir, Tajikistan
Sediment sources - geological Indus Valley • Directly into the reservoir • Geological • Accelerated erosion 9
Sediment sources - geological Mudslide, Tajikistan 01/09/2019 10
Sediment sources - geological 01/09/2019 Young River New Zealand 11
Sediment sources - geological Tarbela Dam Pakistan Loss of 18% of live storage after 25 years (WCD) 12
AdvWainthtoaugt ReessearnvodirsDisadvantages Supplement sand for building Maintain wetland materials More nutrient for ecosystem soil and crops Forest Reduce acid and development help soil reclamation Present river SEDIMENTATION More deposition bank and coastal Reduce and extending erosion life expectancy for water works land More cost for More food for dinking water fishes and treatment planktons 13
Advantages and Disadvantages With Reservoirs Supplement sand for building Maintain wetland materials More nutrient for ecosystem soil and crops Forest Reduce acid and development help soil reclamation Present river SEDIMENTATION More deposition bank and coastal and extending Reduce erosion life expectancy land More cost for for water works dinking water More food for treatment fishes and planktons 14
1.4. Erosion and sedimentation Social and environmental risks • Downstream erosion • Loss of sediment deposition for floodplains • Loss of river bank gardens downstream • Changes in river morphology • Affect Dam and community safety • Cause social issues 15
1.5. Reservoir Sedimentation impacts River bank erosion can result from sediment reduction and fluctuating water levels (NHI 2013) 16
INTEGRATED AND 2008 SUSTAINABLE 1971 WATER 1989 MANAGEMENT OF RED-THAI BINH RIVER SYSTEM IN A CHANGING CLIMATE (IMRR PROJECT) 2010 Water intake 17 elevation of the Pump is above water level
1.5. Sedimentation impacts Problem of hydropower (erosion) + sand mining Hanoi Hanoi 6 Jan & Feb water levels 2500 Jan & Feb discharges 5.5 2000 Water level (m)5 1500 Discharge (m3/s)4.5 Flow is 4 1000 hungry of 3.5 sediments 3 2.5 500 2 0 1.5 1 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 Date Date 18
1.5. Sedimentation impacts Observed hydromorphologial changes • Exponentially increased flow routing toward the Duong (2000-2010) 19
Preventing stream capture – costs of a posteriori solutions Mossa, 1996 Estimated costs 1960-present > 500 Mio $ • No final, resilient solution 20
1.6. Sediment management techniques? 1, 5 3 2,4 21
Some key messages 1. Reservoir sedimentation is a major problem, worldwide 2. Sedimentation rates have often been under-estimated in feasibility studies, and Sediment risks are often not well understood 3. Reservoir bank collapse is a major problem for some reservoirs. Sediment trapping can affect project financial viability 4. Geological sediment inputs cannot be reduced, while sediment inputs from accelerated (man-made) erosion can be reduced – with effort 5. Downstream bank erosion can result in loss of land for agriculture and other uses 22
Some key messages 6. There are various options for designing hydropower projects to minimise sediment problems. 7. Baseline data should be collected during feasibility and EIA studies to investigate technical, social and environmental risks 8. A scientific approach is needed for monitoring design and data collection 9. Design and operating measures are needed to manage risks 10. There is a lack of sediment data in the Mekong basin to inform planning and decision making on hydropower sediment management 23
QUESTIONS? COMMENTS Day 3 Morning Coffee Break https://www.youtube.com/watch?v=g3OViIA1Emc 24
2. Watershed management https://www.youtube.com/w atch?v=f63pwrMXkV4 25
2. Watershed management UK USA General Basin Catchment Watershed Watershed Divide 26
2. Watershed management Why? The costs of poor water management are large: Groundwater depletion takes 2.1% off Jordan's GDP; Water pollution and scarcity knock 2.3% off China's; < cost for restorationCost fo1r1%proefvKeenntya's was lost to flooding in 1997-98, and 16% to drought in the next two years. http://www.economist.com/node/16136280 What? • Manage the land to change the hydrology • Manage the land to benefit the people 27
2. Watershed management Source: DFID 1998, after MRC-GIZ Cooperation Programme 28 Coppin & Richards, 1990
2. Watershed management: Changing hydrographs Physical objectives: • Slower runoff • Reduced flood peaks • Less erosion and sediment transport • Higher baseflow • Can also manage for increased runoff 01/09/2019 29
2.1. Watershed management: IWRM concepts The World Summit on Sustainable Development in 1992 in Rio made the concepts: 'IWRM is a process which promotes the coordinated development and management of water, land and related resources, in order to maximize the resultant economic and social welfare in an equitable manner without compromising the sustainability of vital ecosystems.‘ Source Integrated Water Resources Management in Action. WWAP, DHI Water Policy, UNEP-DHI Centre for Water and Environment. 2009 30
Watershed management – IWRM principles? 1. Water is finite and vulnerable resource Fresh water is a finite and vulnerable resource, essential to sustain life, development and the environment. 2. Participatory approach Water development and management should be based on a participatory approach, involving users, planners and policy-makers at all levels. 3. Role of women Women play a central part in the provision, management and safeguarding of water. 4. Social and economic value of water Water is a public good and has a social and economic value in all its competing uses. Source: http://www.gwp.org/en/ToolBox/ABOUT/IWRM-Plans/IWRM- 31 Principles/Participatory-approach/
BEFORE INTERVENTION UPSTREAM DOWNSTREAM 32
UPSTREAM DOWNSTREAM 33
FOREST AND HYDROLOGICAL REGIME Simulated Maximum flow at some stations Station Qmax Simulate Simulate Difference Difference measure d Qmax - d Qmax - Forest Forest (m3/s) (%) d (m3/s) 1993 2005 (m3/s) (m3/s) Nong 7030 6454.3 6636.5 182.2 2.8 Son 4540 4121.6 4340 218.4 5.3 Thanh My http://www.vawr.org.vn/index.aspx?aac=CLICK&aid=ARTICLE_DETAIL&ari=2027&lang= 1&menu=khoa-hoc-cong-nghe&mid=995&parentmid=0&pid=1&title=kha-nang-ung- dung-mo-hinh-swat-de-danh-gia-vai-tro-cua-rung-doi-voi-lu-luu-vuc-song-vu-gia---thu- bon 34
UPSTREAM IWRM «RIDGE TO REEFS» APPROACH DOWNSTREAM 35
2.2. Six factors-contributors to catchment management approach • Poor catchment condition, which can dramatically reduce project life; • The rights of basin residents; • Participatory project planning processes becoming more common and effective. Residents of affected areas are better placed to demand and achieve benefits • Regional effects of major water infrastructure schemes can be catalysts for regional economic and social development and watershed protection • Efforts to reverse environmental degradation at the river basin level becoming more common • Existing projects were designed on Climate change, as well as increasing uncertainty for new projects 36
2.3. Watershed interventions Hard Soft Water storage Land use planning Flood proofing (control) Early warning systems Education Demand management
2.3. Watershed interventions Hard Soft Water storage Flood proofing (control) Land use planning, Regulation, Early warning systems institutional Arrangement Education Demand management
Watershed management - does it work? Physically: • Yes, at small and (sometimes) medium scales • Less effective, at large scales and for major events (e.g. 100-year rainfall) Socially: • Yes - with the right incentives 39
Key messages 1. Watershed management involves changing the land surface to cause changes in the hydrology of the watercourse flowing from it 2. Watershed management can affect more hydrology in small catchment and sometimes in medium sized catchments. 3. Achieving changes in land management is very difficult when watersheds are inhabited since this requires changes in the knowledge, attitude and practice of local resource users. 4. Measuring the effects of watershed management on hydrology is difficult and requires long time –series data 40
QUESTIONS AND COMMENTS 41
3. GROUP WORK (4 groups) Share problems and experiences in watershed management in Myanmar Ayeyarwaddy River Thanlwin River Chindwin River Sittaung River 42
3. GROUP tasks) 1. Draw your Watershed on A0 2. Describe Institutional Arrangement of the Watershed 3. Insert the works/projects have been done 4. List Mayjor Issues 01/09/2019
4. Payment for Ecosystem Services 4.1. Principles? • Users / beneficiaries of ecosystem services pay stewards / providers of those services • Usually voluntary • Usually direct payments • Payments are additional to normal financing • Payments are conditional on receiving the services PES lie in the principle of mutually beneficial bargaining, through bargaining, two parties may arrive at an adequate location of and environmental resource that is social eficient 44
Payment for Ecosystem Services (PES) Typical services • Carbon sequestration (absorb) • Watershed protection • Biodiversity conservation • Scenic beauty Buyers Sellers Ecosystem Hydropower Forest owners Services Companies Water companies Land users Local residents Etc... Recreational users Insurance groups Economic incentives to Conservation groups sustainable use of ES 45
4.2. PES Payment Approaches Output-based Input-based payments payments Payments Payments for the based directly adoption of particular on the delivery land uses or land of ecosystem management services (also practices that are be referred to as expected to deliver payments for additional ecosystem services and benefits results). E.g. USD/hectare E.g. USD/KWh 46 or USD/m3
PES Advantages Limits Efficiency A good undestanding Sustainability Needs continous readjusting Autofinancing Market-based (quantifiable services) Transaction costs Not necessarily a poverty reduction mechanism A substantial role for governments will remain 47
4.3. PES - UPTAKE 1997 Costa Rica 2003 2008 Mexico 2010 Ecuador Vietnam: Decree 99/ND-CP dated 24/09/2010 Payment for Forest Environmental Services 48 01/09/2019
PES in Costa Rica Forest Law (1996):four primary purposes for the Program: (1) Mitigation of greenhouse gas emissions; (2) Hydrologic services, including provision of water for human consumption, irrigation, and energy production; (3) biodiversity conservation; and (4) protection of scenic beauty for recreation and ecotourism. The Law also established a regulatory framework for contracting with landowners for the provision of these services. Landowners submit a plan for sustainable forest management. Forester must adopt specified practices (i.e. timber plantation, forest conservation or forest management) Annual payments for forest conservation averaged US$64/hectare. For forest plantations, approximately US$816/hectare 49
PES in Ecuador In the 1990s the Ministry of Environment commissioned a local environmental NGO, Fundación Antisana (FUNAN) to control the threats: water contamination, sediment, upland water source – degradation ……impacts on hydrological functioning. FUNAN identified 5 key actions: 1. Watershed valuation 2. Land purchase or compensation measures 3. Enforcement of protection 4. Targeted land management 5. Sustainable production systems Financial sourse: International Donor, PES, & endowments. Seed fund 2000: USD 20.000 2005: USD 2.5 mil. 50
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