DEPARTMENT OF GEOGRAPHY WETLAND RESEARCH UNIT Hydrological modelling of climate change impacts on Loktak Lake, India C.R. Singh, J.R. Thompson & D. Kingston Wetland Research Unit / Environment Modelling Group Department of Geography University College London [email protected] DEPARTMENT OF GEOGRAPHY WETLAND RESEARCH UNIT Outline: • Loktak Lake Ecosystem • The coupled MIKE SHE / MIKE 11 system • MIKE SHE / MIKE 11 modelling of the Loktak Lake catchments • Hydrological modelling of climate change impacts • Implications for lake water balance DEPARTMENT OF GEOGRAPHY WETLAND RESEARCH UNIT Location: Nepal Bhutan Lake area: 2 = 287 km Loktak India Lake China Mean lake depth: Bangladesh = 2.5 m I r r a w a d y R i v e r B a s i n Myanmar (Burma) B a y Laos o f B e n g a l Thailand DEPARTMENT OF GEOGRAPHY WETLAND RESEARCH UNIT Loktak Lake - lifeline of Manipur • Livelihood of 0.27 million people • Habitat for rare and endangered species e.g. Cervus eldi eldi • Traditionally managed by communities for fisheries and agriculture • Breeding ground of a number of riverine fish and a vital fisheries resource. Designated a Wetland of International Importance (Ramsar Convention) in 1990 DEPARTMENT OF GEOGRAPHY WETLAND RESEARCH UNIT Problems and Issues Ithai Barrage commissioned in 1982: Manipur River • Generation of 105 MW HEP (58.8 m3s-1) Basin • Irrigating 24,300 ha of land under Loktak Lake Irrigation scheme (17 m3s-1) Loktak Power channel Lake Ithai Barrage DEPARTMENT OF GEOGRAPHY WETLAND RESEARCH UNIT Problems and Issues • Weed infestation (phumdis proliferation) • Decreased water holding capacity • Pollution • Decreased fisheries production • Loss of biodiversity • Flooding of adjacent agricultural land • Degradation of habitat of Sangai deer (KLNP) • Encroachment by human activities DEPARTMENT OF GEOGRAPHY WETLAND RESEARCH UNIT Catchment Area Total catchment area = 5200 km2 Cross-section profile 2068 m. Naga / Kuki Villages Meitei Villages Floating Huts on ‘Phumdis’ x x 780 m. Dryland Crops Dense Forest Dense Degraded Forest Degraded Grasslands/ Scrubs Rice Paddy Lake LAND USE Loktak COMMUNITY Hillside Communities Shore Dwellers Hut Dwellers POPULATION 50,263 persons / 278,935 persons / 1,977 persons / 96 villages 53 settlements 733 floating huts DEPARTMENT OF GEOGRAPHY WETLAND RESEARCH UNIT Landuse Legend Agriculture Dense Forest Degraded Forest Shifting Cultivation Settlement Water bodies Phumdis DEPARTMENT OF GEOGRAPHY WETLAND RESEARCH UNIT Mean Monthly Rainfall Meteorological Profile 300 250 • Annual Rainfall: 1409 mm 200 • 75% of the annual rainfall during 150 the monsoon months of June – 100 Rainfall (mm) Rainfall October 50 • Climate change is likely 0 Jul Apr Jun Oct Jan Aug Feb Sep Mar Nov Dec to modify meteorological May conditions Mean Monthly Evapotranspiration 140 • Evaluation of impacts 120 through modelling 100 80 ET (mm) ET 60 40 20 0 Jul Apr Jun Oct Jan Aug Feb Sep Mar Nov Dec May DEPARTMENT OF GEOGRAPHY WETLAND RESEARCH UNIT The MIKE SHE / MIKE 11 Hydrological Modelling System Fully Distributed Model: Saturated zone Unsaturated zone Evapotranspiration Overland flow Channel flow MIKE 11 1D river model - dynamic coupling DEPARTMENT OF GEOGRAPHY WETLAND RESEARCH UNIT Model Conceptualization • 8 sub catchments • Stream gauging stations in 3 sub catchments • Model calibration with Thoubal River • Validation with Iril and Nambul River DEPARTMENT OF GEOGRAPHY WETLAND RESEARCH UNIT Model Conceptualization Rainfall-discharge relation Model validation (Iril River) Rainfall-discharge relation Model parameters Model Model calibration Ungauged (Thoubal River) catchments Rainfall-discharge relation Model validation (Nambul River) Model parameters Model DEPARTMENT OF GEOGRAPHY WETLAND RESEARCH UNIT MIKE SHE Model Set Up for Thoubal River • Model area: 963 km2 • Grid size: 600m x 600m DEPARTMENT OF GEOGRAPHY WETLAND RESEARCH UNIT MIKE SHE Model Set Up for Thoubal River Input Data : • Rainfall (1999-2003) • Evapotranspiration • Discharge (1999-2003) • Landuse • Topographic map • Drainage map • Vegetation • Soil profile DEPARTMENT OF GEOGRAPHY WETLAND RESEARCH UNIT MIKE 11 Model Set Up for Thoubal River • Drainage network • 8 Tributaries • Cross-section details • Boundary conditions DEPARTMENT OF GEOGRAPHY WETLAND RESEARCH UNIT Model Calibration • Calibration period: June 1999 – May 2003 (* March - May 1999 data used for initial model stabilisation) • Basis of calibration : Discharge (Stream gauging station) • Calibration parameters : - Hydraulic conductivity (Horizontal & vertical) - Overland flow resistance (Mannings number) - Unsaturated zone infiltration rate - Bed resistance (Mannings number) DEPARTMENT OF GEOGRAPHY WETLAND RESEARCH UNIT Model Calibration Observed and simulated discharge 350 MQ OQ 300 R (correlation) = 0.95 R2(Nash_Sutcliffe = 0.86 s) 250 3 Difference in MDF in discharge = 2% 200 Hydrological regime (mean monthly discharge) 150 70 MQ Discharge (m Discharge 100 OQ 60 50 50 0 s) 3 40 01/06/99 01/12/99 01/06/00 01/12/00 01/06/01 01/12/01 01/06/02 01/12/02 30 MQ 20 350 (m Discharge OQ 300 10 250 s) 3 200 0 Jul Apr Jun Oct Jan Aug Feb Sep Mar Nov Dec 150 May 100 Discharge (m Discharge 50 0 01/06/00 01/07/00 01/08/00 01/09/00 01/10/00 DEPARTMENT OF GEOGRAPHY WETLAND RESEARCH UNIT Model Validation Nambul: Observed and simulated discharge Nambul: Hydrological regime MQ 14 100 OQ MQ 12 OQ 80 R (correlation) = 0.91 R2(Nash_Sutcliffe = 0.82 (m3s) Difference in MDF = 5% 10 60 (m3s) 8 40 Discharge Discharge 6 Discharge 20 4 0 2 0 Jul Apr Jun Oct Jan Aug Feb Sep Mar Nov Dec May 01/06/1999 01/12/1999 01/06/2000 01/12/2000 01/06/2001 01/12/2001 01/06/2002 01/12/2002 01/06/2003 Iril: Observed and simulated discharge Iril: Hydrological regime MQ MQ 80 360 OQ OQ 70 300 R (correlation) = 0.93 60 (m3s) 240 R2(Nash_Sutcliffe = 0.84 Difference in MDF = 7% (m3s) 50 180 40 Discharge 120 Discharge 30 60 20 0 10 0 Jul Jun 01/06/1999 01/12/1999 01/06/2000 01/12/2000 01/06/2001 01/12/2001 01/06/2002 01/12/2002 01/06/2003 Oct Jan Apr Feb Aug Mar Sep Dec Nov May DEPARTMENT OF GEOGRAPHY WETLAND RESEARCH UNIT Discharge estimation for ungauged catchments Ungauged River Area (km2) Nearest Gauged River Area (km2) Area Ratio Imphal 354 Iril 1271 0.28 Kongba 120 Iril 1271 0.09 Heirok 405 Thoubal 963 0.42 Sekmai 301 Thoubal 963 0.31 Sekmai: Monthly Mean Discharge 40 ) -1 s 3 30 20 10 Discharge (m Discharge 0 Jun-99 Jun-00 Jun-01 Jun-02 Jun-03 Sep-99 Dec-99 Mar-00 Sep-00 Dec-00 Mar-01 Sep-01 Dec-01 Mar-02 Sep-02 Dec-02 Mar-03 DEPARTMENT OF GEOGRAPHY WETLAND RESEARCH UNIT Climate Change Scenario - Increase by 2oC & 4oC Based on comparison of gridded historical and future meteorological data (CRU TS3 data provided by NERC QUEST project – UCL and others) Rainfall Average (1974-2003) Monthly Rainfall Avg. % Change Forcing of model in time series rainfall Monthly Rainfall data Rainfall Average (2040-2069) Monthly Rainfall Re-run model using new meteorological time series Average Temperature Monthly Potential (1974-2003) Evapotranspiration (PET) Avg. % Change Forcing of model time in series PET data Monthly PET Temperature Average (2040-2069) Monthly PET DEPARTMENT OF GEOGRAPHY WETLAND RESEARCH UNIT Impacts of Climate Change on Thoubal River Monthly Rainfall 2ºC Increase Scenario Monthly PET 800 300 Climate Change Climate Change 700 Observed 250 Observed 600 200 500 400 150 PET (mm) PET Rainfall(mm) 300 100 200 100 50 0 0 Jun-99 Dec-99 Jun-00 Dec-00 Jun-01 Dec-01 Jun-02 Dec-02 Jun-99 Dec-99 Jun-00 Dec-00 Jun-01 Dec-01 Jun-02 Dec-02 Jun-03 Monthly Rainfall 4ºC Increase Scenario Monthly PET 800 Climate Change 300 Climate Change 700 Observed 250 Observed 600 500 200 400 150 PET (mm) PET Rainfall(mm) 300 100 200 50 100 0 0 Jun-99 Dec-99 Jun-00 Dec-00 Jun-01 Dec-01 Jun-02 Dec-02 Jun-99 Dec-99 Jun-00 Dec-00 Jun-01 Dec-01 Jun-02 Dec-02 Jun-03 WETLAND RESEARCH UNIT RESEARCH WETLAND GEOGRAPHY OF DEPARTMENT Impacts of Climate Change on Thoubal River Thoubal on Change of Climate Impacts 600 Climate Change 500 Observed 400 300 200 100 PPT (mm)PPT 0 -100 -200 Jun-99 Jun-00 Jun-01 Jun-02 Dec-99 Mar-00 Sep-00 Dec-00 Mar-01 Sep-01 Dec-01 Mar-02 Sep-02 Dec-02 Mar-03 -300 Sep-99 Net Precipitation 2 Precipitation Net Net Precipitation 4 Precipitation Net 600 Climate Change 500 Observed 400 300 200 100 PPT (mm)PPT 0 º º -100 C C -200 Jun-99 Jun-00 Jun-01 Jun-02 Dec-99 Mar-00 Sep-00 Dec-00 Mar-01 Sep-01 Dec-01 Mar-02 Sep-02 Dec-02 Mar-03 -300 Sep-99 DEPARTMENT OF GEOGRAPHY WETLAND RESEARCH UNIT Impacts of Climate Change on Thoubal River Daily Discharge : 2ºC Increase Scenario 400 Climate Change Observed 300 200 100 Discharge (cumec) Discharge 0 01/06/99 01/12/99 01/06/00 01/12/00 01/06/01 01/12/01 01/06/02 01/12/02 01/06/03 Daily Discharge : 4ºC Increase Scenario 400 Climate Change Observed 300 200 100 Discharge (cumec) Discharge 0 01/06/99 01/12/99 01/06/00 01/12/00 01/06/01 01/12/01 01/06/02 01/12/02 01/06/03 DEPARTMENT OF GEOGRAPHY WETLAND RESEARCH UNIT Impacts of Climate Change on Thoubal River Mean Monthly Discharge : 2ºC Increase Scenario 160 Observed Climate Change 120 80 40 Discharge(cumecs) 0 Jun-99 Dec-99 Jun-00 Dec-00 Jun-01 Dec-01 Jun-02 Dec-02 Jun-03 Mean Monthly Discharge : 4ºC Increase Scenario 160 Observed Climate Change 120 80 40 Discharge(cumecs) 0 Jun-99 Dec-99 Jun-00 Dec-00 Jun-01 Dec-01 Jun-02 Dec-02 Jun-03 WETLAND RESEARCH UNIT RESEARCH WETLAND GEOGRAPHY OF DEPARTMENT Mean Monthly Discharge Monthly Mean Impacts of Climate Change on Iril River Iril on Change of Climate Impacts 200 Observed 2 Degree ) 160 -1 s 4 Degree 3 120 80 Discharge(m 40 0 Jun-99