COPING WITH EXTREMES THE IMPACT OF WATER SUPPLY INFRASTRUCTURE ON FLOODS AND DROUGHT AND THE IMPLICATIONS FOR FOOD SECURITY

Tarek Ketelsen, Simon Tilleard, Arun Parameswaran, Mai Ky Vinh

Assessing variability in the Angkor hydroclimate

Source: Buckley et al (2010)

• 1250-1450 extreme fluctuations in drought & storm conditions:

mega-drought 1330s -1360s

more severe but shorter drought 1400s -1420s

Interspersed by high magnitude monsoon years

• Two severe droughts punctuated by heavy monsoon rain weakened the kingdom by:

– shrinking water supplies for drinking

and agriculture

– damaging Angkor's vast irrigation

system which was central to it’s economy

Source: Day et al (2011)

“…the Khmer water management system is a vivid example of a sophisticated human technology that failed in the face of extreme (threshold) environmental conditions.”

Day et al, 2011

WSI expansion in the Mekong Basin

By 2030

• Hydropower => quadruple

• Irrigation command area => double

• How will the Mekong’s current WSI handle extremes in hydroclimate?

Key research questions

1. Do WSI modulate the frequency and severity of droughts and floods?

2. How do descriptions of droughts and floods vary between the various stakeholders and genders upstream and downstream of WSI infrastructure?

3. Have impacts of drought and floods diminished with dams and other WSI?

4. Through their effects on flood and drought, have WSI enhanced food security?

5. How can WSI design and management be improved to enhance their contribution to food security?

Main components of the study

1. Assessment of the Mekong flood & drought regime

2. GIS database of Mekong WSI and their capacity to regulate extremes

3. Regulating effects of WSI during hydroclimate extremes

4. Documentation of d/s community coping strategies during hydroclimate extremes

5. Implications for food security

Basin wide assessment

• focus will be hydropower

• regional review of floods and droughts and food security in the Mekong Basin – Definitions of extreme hydro-climate conditions in the Mekong

– Characterisation of their role in Mekong productivity

• develop a consolidated inventory of WSI in the basin. – Dam characteristics

– Catchment characteristics

– Downstream user characteristics.

Case study assessment• with Institute of Water Resource Planning (IWRP) and Enterprise

Development Institute (EDI)

• selection based on preliminary findings of the basin-wide review & consultations with key government agencies

• select one WSI in Cambodia and one in Vietnam and conduct computational modelling, community surveys and participatory consultations to understand how the downstream communities experience of floods and droughts have changed due to the introduction of WSI.

• develop an understanding of how WSI have impacted food security (both positive and negative) and scope implications of improvements to management.

Typical Reservoir Management for Electricity Generation:flood management considerations

1

2

3

4

Dry Season Wet Season

Full Supply Level

Low Supply Level

Live Storage

Dead Storage

Source: Räsänen et al, under publication

Allowance forFlood Storage??

1. Dry SeasonLow rainfall and plant operation begins to lower storage level

2. End of the Dry SeasonStorage level continues to drop towards Low Supply Level

3. Start of the Wet SeasonHigh rainfall causes storage level to rise

4. Dam at full capacityEarly wet season, Full Supply Level reached and maintained.

Storms

Storms and peak eventsAverage maximum daily

precipitation (1985-2005)

Source: MRC, 2010

Towards a flood control index….

1. Reservoir characteristics- Management and operational rules- Regulating Capacity (storage/MAF)- Spillway and plant discharge capacities- Freeboard capacity

2. Sub-catchment characteristics- Response time to storm events- Precipitation dynamics- Storm frequency and intensity- River flow and networks

3. Downstream considerations- Population Density- Land use characteristics- Infrastructure assets

Flood Control Index

Low capacity to regulate floods

High capacity to regulate floods

Towards a flood control index….

Thank you for your attention