WATER RESOURCES UNIT Stakeholders Workshop to Implement a

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WATER RESOURCES UNIT Stakeholders Workshop to Implement a Pilot Project on Impact-based Forecasting and

WATER RESOURCES UNIT Stakeholders Workshop to Implement a Pilot Project on Impact-based Forecasting and Risk-based Warnings 26 -30 October 2015 Presentation on: “Coping with hazards that affect day-to-day operations and activities at the Water Resources Unit” by M. K. Bissessur Civil Engineer at Water Resources Unit

Overview of Presentation w Water Resources Sector in Mauritius w Hazards/Challenges w Adaptation Measures

Overview of Presentation w Water Resources Sector in Mauritius w Hazards/Challenges w Adaptation Measures w Long Term Plan

INSTITUTIONAL ARRANGEMENT WMA CWA WRU CEB IA Water Resources Unit Responsible for the Assessment,

INSTITUTIONAL ARRANGEMENT WMA CWA WRU CEB IA Water Resources Unit Responsible for the Assessment, Mobilisation, Control, Development, Management and Conservation of Water Resources in Mauritius

WATER BALANCE FOR MAURITIUS Area of Mauritius Annual average rainfall Annual volume of raw

WATER BALANCE FOR MAURITIUS Area of Mauritius Annual average rainfall Annual volume of raw water Estimated water utilizable potential (33%) : 1865 km 2 : 2100 mm : 3900 Mm 3 : 1300 Mm 3

Annual Rainfall Average 2100 mm Varies from a max of 4000 mm in the

Annual Rainfall Average 2100 mm Varies from a max of 4000 mm in the higher elevation in the Centre to 800 mm in the West 1200 mm in the North

Observation Network of Water Resources in Mauritius Gauging stations on Rivers No: 150

Observation Network of Water Resources in Mauritius Gauging stations on Rivers No: 150

Boreholes Observation wells No. : 260

Boreholes Observation wells No. : 260

Hazards/Challenges w Ageing Infrastructure • Dams and Reservoirs • Feeder Canals w Reservoirs and

Hazards/Challenges w Ageing Infrastructure • Dams and Reservoirs • Feeder Canals w Reservoirs and Feeder Canals Operations w Surface and Underground Water w Water Supply Quality

Hazards/Challenges w Ageing Infrastructure • Dams and Reservoir Infrastructures – Safety Analysis of Dams

Hazards/Challenges w Ageing Infrastructure • Dams and Reservoir Infrastructures – Safety Analysis of Dams in Mauritius 1999 – Rehabilitation Programme in place (Mare aux Vacoas, Municipal Dike, La Nicoliere Reservoir already rehabilitated) – Control of Development Upstream and Downstream of Dam – Dam Safety Inspection • Daily Monitoring of Reservoir Level, Inflows and Outflows • Piezometric Level • Survey Pillars Level • Seepage Monitoring • Visual Inspection Upstream and Downstream Embankment • Spillway Channel • Upstream/Periphery of Reservoir- Landslide Survey • Post Disaster Monitoring

Hazards/Challenges w Ageing Infrastructure • Feeder Canals – Consultancy services for the assessment and

Hazards/Challenges w Ageing Infrastructure • Feeder Canals – Consultancy services for the assessment and upgrading of existing feeder canals in Mauritius – Trianon Grosses Roches Feeder Canal & La Nicoliere Feeder Canal already rehabilitated

Hazards/Challenges w Reservoirs and Feeder Canals Operations • Main Reservoirs – Spill Channel Monitoring

Hazards/Challenges w Reservoirs and Feeder Canals Operations • Main Reservoirs – Spill Channel Monitoring – Regulating of outflows prior to spilling – Storm runoff basin during heavy rainfall (buffer 3 -4%) • Feeder Canals – Ongoing Canal Inspection Programme • Siltation • Obstruction by debris • Overflow of canal-Raising of Canal Wall at critical places • Valve Operation-Emergency Drawdown – Daily Monitoring of canal flows – Daily Monitoring & Regulating Flows in Diversion Channel – Immediate Closure of Canal during heavy rainfall and cyclones – Ongoing Maintenance works of infrastructures

Midlands Reservoir -La Nicolière Reservoir Water Transfer System

Midlands Reservoir -La Nicolière Reservoir Water Transfer System

Flow Measuring Stations on Diversion and Feeder Canals

Flow Measuring Stations on Diversion and Feeder Canals

Hazards/Challenges w Surface and Underground Water w Ground Water Recharge Rate o Increase surface

Hazards/Challenges w Surface and Underground Water w Ground Water Recharge Rate o Increase surface runoff o Recharge time of aquifer w Urbanization o Change in landform pattern and final discharge points o Successive Peak Flows causing flooding w Water Rights o Less agricultural development and new urbanization development o Transition of existing irrigation ponds into storm water impounding characteristics for residential development

Hazards/Challenges w Water Supply Quality-Urbanization w Siltation in Reservoir o More land erosion and

Hazards/Challenges w Water Supply Quality-Urbanization w Siltation in Reservoir o More land erosion and frequent accumulation of silts w Clogging of Filters o Illegal discharges and impact on raw water quality w Accumulation of Debris o Solid wastes and floating debris

Adaptation Measures w Safety Analysis of Dams in Mauritius – Rehabilitation of La Ferme

Adaptation Measures w Safety Analysis of Dams in Mauritius – Rehabilitation of La Ferme reservoir w Rehabilitation Programme of Dams and Feeder canals – Rehabilitation of La Fenetre Feeder Canal w Connectivity between Reservoirs – Midlands to Piton du Millieu, Mare Longue to Mare aux Vacoas w Dam Break Analysis for new Dams w New Dam Designs as per ICOLD recommendations w Emergency Preparedness Plans

Long Term Plan w Legislative Framework – Reinforcing existing legislations – Enactment of new

Long Term Plan w Legislative Framework – Reinforcing existing legislations – Enactment of new laws w Capacity Building – Training and logistics w Up to date Technology – Rainfall Data Capture – River Flow Gauging – Early Warning w Hydrological Catchment Preservation Plans w Construction of new dams w Control of development and setback distances from rivers and dams w Rehabilitation of dam – Holistic approach (urbanization)

THANK YOU

THANK YOU