Hydrological Modelling of Climate Change Impacts on Loktak Lake, India

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

ET (mm) ET 60

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

s) 3

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

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

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

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

)

-1 s

3 30

10 Discharge (m Discharge

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 DEPARTMENT OF GEOGRAPHY WETLAND RESEARCH UNIT Impacts of Climate Change on Thoubal River

Net Precipitation 2ºC

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 4ºC 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 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

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

40 Discharge(cumecs)

0 Jun-99 Dec-99 Jun-00 Dec-00 Jun-01 Dec-01 Jun-02 Dec-02 Jun-03 DEPARTMENT OF GEOGRAPHY WETLAND RESEARCH UNIT Impacts of Climate Change on Iril River

Mean Monthly Discharge

200 Observed 2 Degree

) 160 -1

s 4 Degree 3 120

Discharge(m 40

Jun-99 Jun-00 Jun-01 Jun-02

Apr-00 Apr-01 Apr-02 Apr-03

Oct-99 Oct-00 Oct-01 Oct-02

Aug-99 Feb-00 Aug-00 Feb-01 Aug-01 Feb-02 Aug-02 Feb-03

Dec-99 Dec-00 Dec-01 Dec-02 DEPARTMENT OF GEOGRAPHY WETLAND RESEARCH UNIT Impacts of Climate Change on Nambul River

Mean Monthly Discharge 30 Observed

) 25 2 Degree

-1 s

3 4 Degree 20 15 10

Discharge (m Discharge 5

Jun-99 Jun-00 Jun-01 Jun-02

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 Impacts of Climate Change on Ungauged Rivers

River Mean Daily Discharge (m3s)

Model 2ºC Change 4ºC Change

Khuga 13.87 15.32 16.93

Imphal 9.59 10.51 11.50

Heirok 10.06 11.05 12.19

Sekmai 7.16 7.87 8.71

Western Catchment 27.18 30.01 33.56

Kongba 3.32 3.64 3.97 DEPARTMENT OF GEOGRAPHY WETLAND RESEARCH UNIT Impacts of Climate Change on Wetland Water Balance

Water Balance:

Inflow (rivers) + direct precipitation – Evapotranspiration – Open water evaporation – HEP abstraction – Barrage release

DP RI • 70% of the lake surface is covered with E phumdis ( floating vegetation mass) PET HP BR DEPARTMENT OF GEOGRAPHY WETLAND RESEARCH UNIT Impacts of Climate Change on Wetland Water Balance

2000 Current 1800 2 Degree 1600 4 Degree 1400 1200 River Inflow 1000 800 600

Volume (Mcum)Volume 400 200 0 Current 150

2 Degree

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-03 120 4 Degree 90 Precipitation 60

Volume (Mcum) Volume 30

0 Current 150

2 Degree

Jun-99 Jun-00 Jun-01 Jun-02 Jun-03

Mar-00 Mar-01 Mar-02 Mar-03

Sep-99 Sep-00 Sep-01 Sep-02

Dec-99 Dec-00 Dec-01 Dec-02 120 4 Degree 90 PET 60

Volume (Mcum) Volume 30

0 Current 150

2 Degree

Jun-99 Jun-00 Jun-01 Jun-02 Jun-03

Mar-00 Mar-01 Mar-02 Mar-03

Sep-99 Sep-00 Sep-01 Sep-02

Dec-99 Dec-00 Dec-01 Dec-02 120 4 Degree 90 60 Evaporation

Volume (Mcum) Volume 30

0 Current 1200

2 Degree

Jun-99 Jun-00 Jun-01 Jun-02 Jun-03

Mar-00 Mar-01 Mar-02 Mar-03

Sep-99 Sep-00 Sep-01 Sep-02

Dec-00 Dec-01 Dec-02 900 Dec-99 4 Degree 600 Barrage 300 Volume (Mcum) Volume Release

Mar-00 Mar-01 Mar-02 Mar-03

Jun-99 Jun-00 Jun-01 Jun-02 Jun-03

Sep-99 Dec-99 Sep-00 Dec-00 Sep-01 Dec-01 Sep-02 Dec-02 DEPARTMENT OF GEOGRAPHY WETLAND RESEARCH UNIT Impacts of Climate Change on Wetland Water Balance

Monthly Water Balance 2000 Current 2 Degree 1500 4 Degree

1000

500

Volume(Mcum) 0

-500

Jun-99 Jun-00 Jun-01 Jun-02 Jun-03

Dec-99 Dec-00 Dec-01 Dec-02

-1000

• Get wetter during the monsoon period DEPARTMENT OF GEOGRAPHY WETLAND RESEARCH UNIT Conclusions:

• MIKE SHE / MIKE 11 system modelling get a good fit

• Climate change implications:

- Increase discharge from the catchment area

- Increase inflow into the lake (wetter in wet period)

• Change in the water level of the lake DEPARTMENT OF GEOGRAPHY WETLAND RESEARCH UNIT

Acknowledgements

• Department of Geography, UCL Ted Hollis Scholarship in Wetland Hydrology and Conservation

• UCL Graduate School Conference Fund

• Loktak Development Authority

• Wetlands International DEPARTMENT OF GEOGRAPHY WETLAND RESEARCH UNIT