Assessment of the Impact of Anticipated External Drivers of Change on Water Resources of Coastal Zone
Ganges Basin Development Challenge
Ganges Basin Development ChallengeObjective: Improve resource productivity and increase the resilience ofagriculture and aquaculture systems of brackish coastal areas of the Ganges
What the Ganges BDC Hopes to Achieve?Goal:Reducing poverty, increasing resilience, through improved water governance andmanagement & intensified and diversified agricultural and aquacultural systemsin brackish water of the coastal Ganges.Objective:Improve resource productivity and increase the resilience of agriculture andaquaculture systems of brackish coastal areas of the Ganges.
Ganges Basin:Ganges Basin Area= 1,087,300 sq. km
Study Area:Ganges Dependent Area in BangladeshProject Target Area:Coastal Zone of the Ganges basin inBangladesh except the SundarbansCoastal Divisions:Barisal: Patuakhali, Barguna, Jhalakati &Pirojpur districtsKhulna:Khulna & Satkhira districts
Problems and Challenges in the Coastal Region of Bangladesh Salinity intrusionSea level rise Decrease in precipitation in dry season Salinity intrusion Salinity Intrusion Increase in precipitation in monsoon Increased frequency of tropical cyclone Added siltation on the drainage route Flood Cyclone Water logging
Coastal Polders in Bangladesh In the early sixties and seventies, 125 polders (of which 49 are sea-facing) were constructed to protect low lying coastal areas from tidal flood & salinity intrusion.
Drivers of Change: Participatory ApproachDRIVERS PRESSURE/CONSEQUENCESDemographic/Societal Pressure on SpacePopulation growth Water demand & useDietary patterns of the population Loss of biodiversity and wetlandsLand use change including increase area under rice cultivationUrbanizationEconomic/Trade Shift in land useEconomic develpopment in coastal zone (change in per capiata Water Demandincome) Roads, railway & portsMarket value of agricultural products Water pollutionWater pricing and increaseIndustrializationPolitical/Institutional/Legal Improved Irrigation and drainage systemWater policy (national and regional) Flood protection systemChange in water governance and institutions Water availability in the dry seasonWater sharing mechanisms between the riparian parts of the basinChanges in water management practicesChange in trans-boundary flowEnvironmental/Climate Change Fresh water shortage, Salinity intrusionSea level rise due to Climate Change Flood Hazard,Coastal/fluvial erosionChanges in precipitation and temperature due to Climate Change Change in Sediment balanceSubsidence Cyclone & Storm surge with higher frequency and intensityTechnological/Important Innovations Enhanced knowledge and use of HYVChanges in aquaculture and agriculture intensification Enabling environment for agriculturalWater Use change; Water infrastructure development development
QuestionnaireNameAgeGender Male FemaleOccupationPlease indicate how do you think the external drivers will affect water resources of your area/coastal region ofGanges basin ? Score (1-5) 2. To a very limited significant extent 4. To a significant 3. To a moderate 5. To a very extent extent extent 1. No Sl External Drivers Remarks 1 Do you think the pressure of population growth on water resources will continue in the future? 2 Is market value an important factor in crop divesification? 3 Will sea level rise reduce freshwater availability and land availability for agriculture? 4 Will decrease of rainfall in the dry season and increase in the monsoon renderadverse impact on water resources? 5 Does political change or institutional issues cause any change in water management?
Percentage Population Growth 6.5% Changes in Water Mgt Sea level rise 6.1% 5.9% Land use change Water Sharing 5.7% 5.7% Transboundary flow Aquaculture intensification Economic Develpopment Urbanization Water infrastructure… 5.5% 5.4% 5.4% 5.4% 5.4% Changes in precipitation 5.2% Water Policy 4.8% Industrialization Water Governance &… 4.6% 4.6% Water Use change Preliminary Results of Questionnaire SurveyMarket Value of Agro Products 4.4% 4.3% Changes in temperature 4.2% Dietary patterns 3.2% Water Pricing & Insurance 2.8%
Methodology:Generation of climate change scenario (100 or 200 km grid) (20 to 50 km grid) High resolution regional climate change surface
Ganges, Brammaputra and Meghna Basin Model Bangladesh rivers receive runoff from a catchment of 1.72 million sq. km, around 12 times its land area Brahmaputra Basin 552,000 sq.km CHINA INDIA BHUTAN Ganges Basin 1,087,000 sq.km INDIA BANGLADESH Meghna Basin 82,000 sq.km BAY O F BE N GAL
Methodology: Upstream Boundaries (Q, Sal = 0ppt) Water flow and salinity model for south-west region of Bangladesh Rainfall Evaporation & Other lossWe need:-Cross-section of the rivers- Structure information- Rainfall and evaporation data- Time-series WL, water flow and salinitydata (from primary/secondary sourcesand calibrated Bay of Bengal model)- Measured WL, water flow and salinitydata for calibration and validation Downstream Boundaries (WL, Sal)
Methodology:Land-use management practices and water inflow:SWAT Model:A process-based continuous hydrological model that predicts the impact of landmanagement practices on water, sediment and agricultural chemical yields.Water balance equation: SWt = SWo + Where, SWt = final soil water content (mm) SWo = initial soil water content (mm); t= time (days) Rday = amount of precipitation on day i (mm) Qsurf = amount of surface runoff on day i (mm) Ea = amount of evapotranspiration on day i (mm); Wseep = amount of percolation on day i (mm) Qgw = amount of return flow on day i (mm)
Hydrologic Trend Analysis in the Study Area:Trend Analysis of Upstream River Discharge Hardinge Bridge on the Ganges • Increasing trend of 90000 annual maximum flow 80000 • Decreasing trend of 70000 annual minimum flow 60000Discharge (m3/s) 50000 40000 30000 20000 10000 0 1930 1940 1950 1960 1970 1980 1990 2000 2010 Max Q Min Q Average Q Linear (Max Q) Linear (Min Q) Linear (Average Q)
Hydrologic Trend Analysis in the Study Area:Trend Analysis of Downstream Water Level Hiron Pointon the Pussur River Hiron Pointon the Pussur River • Rising trend of water 4 level near the sea 4 3 3 The increase of maximum 2 water level is 6 cm/yr atWater Level (mPWD)Water Level (mPWD) Hiron Point in the last 10 12 years. 0 1 -1 -2 0 1980 1999 1985 2001 1990 2003 1995 2005 20002007 2005 2009 2010 Max of WL Max of WL of WL Min Linear (Max of WL)of WL Average Linear (Max of WL) Linear (Min of WL) Linear (Average of WL)
Salinity (PPT) 0 2 4 6 8 12 10 Jan/2005 Jan/2005Mar/2005Apr/2005May/2005May/2005Jun/2005 Jul/2005Aug/2005Sep/2005 Noapara GhatOct/2005Nov/2005Dec/2005 Jan/2006Feb/2006Mar/2006Apr/2006May/2006Jun/2006 Fultola Ghat Jul/2006Aug/2006Sep/2006Oct/2006Nov/2006Dec/2006 Jan/2007Feb/2007Mar/2007Apr/2007May/2007 Charerhat GhatJun/2007 Jul/2007Aug/2007Sep/2007Oct/2007Nov/2007Dec/2007 Jan/2008Feb/2008 Rupsha GhatMar/2008Apr/2008May/2008Jun/2008 Jul/2008Aug/2008Sep/2008Oct/2008 Salinity Trend in the Region MollarhatNov/2008Dec/2008 Jan/2009Feb/2009 Monthly Salinity MonitoringMar/2009Apr/2009May/2009Jun/2009 Jul/2009Aug/2009Sep/2009 (Data Source: Department of Environment, DOE)Oct/2009
Impact of SLR: Intrusion of 5ppt Salinity line Dry Season ` 0 SLR 60 cm SLR 120 cm SLRImpact of Sea Level Rise: Intrusion of 5ppt Salinity line(compared to present scenario) Sea Level Rise Affected area (ha) Affected Population (SLR) due to SLR due to SLR 60cm 512,590 4,613,306 120cm 1,061,016 9,549,144
Population growth 140 120• One of the densely 100 populated country 80 60• Projected population 40 20 0 o 2025: 180million o 2050: 220 million Rural Urban Cropped area• Urban: 25 million (2001), 80 Population growth million (2025) & 140 million (2050)• Reduction of agricultural land 1% annually
Projected Coastal population (in million) 57.9 53.6 49.0 46.6 44.2 41.835.12001 2015 2020 2025 2030 2040 2050