QUANTIFYING WATER USER TRADE OFFS AT YALIRESERVOIRBamboo Green Hotel Da Nang, 17th Sept 2013

Nguyen Viet Anh, Tarek Ketelsen, Mai Ky Vinh

MK2: Valuing Multiple uses of reservoir waters: WorldFish – ICEM –IFPRI – CIEM – DLOF - CEPA

Contents

Characteristics of water use

demand

Hydrological Characteristics

Cost and benefit evaluations

between water users

• CIEM carried out the survey within 2km buffer of Yalireservoir

• Surface water availability

• Reservoir water allocation & flows

• Storage capacity and hydro-electricity production

• Economic costs & benefits

• Social costs and benefits

• Conclusion

Research scope• Water shortage occurs in Yali catchment during the dry

season which is affecting agriculture and aquaculture production which are important for the provincial economy

• Yali reservoir has capacity to provide dry season supply, but has not been utilized by provincial users because it was built for electricity production

• There is a perceived water conflict between electricity production and consumptive use by surrounding communities

• The study investigates how significant is this conflict? What is the trade off in electricity production if some reservoir waters are used for community abstraction?

Water consumption

ItemWater Demand (m3/year)

81,328,065

1. Domestic use 937,090

2. Agriculture 76,597,400

Rice 22,160,922

Corn 372,918

Casava 480,971

Tea 10,876,500

Coffee 24,478,816

Sugar cain 17,588,870

Rubber 638,402

3. Aquaculture 360,000

4. Livestock 3,433,575

Cattle 1,209,642

Pig 423,206

Poultry 1,800,727

Overview of the methodology

_

Water availability

Water demand

Water availability

with consumptive

use

Identify critical areas

Rainfall

Inflow

Water demand

Evaporation

_

+ _ OutflowPower

Production

Surface water availability: Moisture budget without consumptive use

Surface water availability: with consumptive use

Water availability in the dry season

Surface water availability• Water availability stays in

surplus during the wet season and mostly in deficit during the dry season

• Surface water stress occurs around Yali reservoir catchment during the dry season (over 300mm deficit)

• Small contribution of water from the reservoir could be used for irrigation within 2km buffer area

• What would be the impact on power production?

Hydrological Model• Using MODSIM hydrological

model which is developed by Colorado State University

• The model was constructed using the following data:– Daily nature inflow to the

reservoir (VMOD)

– Daily precipitation and evaporation

– Water demand

– Storage capacity and power generation (CSUPD)

Evaporation

Precipitation

Scenario 1 - Baseline

• Reservoir is managed exclusively for hydropower production

– On average, the reservoir is full for 78 days over a year (21%)

– Average annual power generated is 3,595 GWh

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

18,000

20,000

0

100,000

200,000

300,000

400,000

500,000

600,000

700,000

800,000

900,000

1,000,000

Jan-01 Jan-02 Jan-03 Jan-04 Jan-05

Ene

rgy

(KW

h)

Live

Sto

rage

Cap

acit

y (1

00

0 m

3)

Reservoir storage Power generation

Scenario 2• Reservoir water is used to

meet 100% of the total water demand by agriculture, domestic and aquaculture uses within a 2km buffer zone around the reservoir

• Annual water demand is 81,328,065m3

0

1000000

2000000

3000000

4000000

5000000

6000000

7000000

8000000

9000000

10000000

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Wat

er

de

man

d (

m3

)

-20%

-18%

-16%

-14%

-12%

-10%

-8%

-6%

-4%

-2%

0%

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Ch

ange

Reservoir storage Power generation

Scenario 2 compared to Baseline

Wet season

Scenario 2 findings• Annual storage capacity and

power production are expected to reduce by 0.7% and 1% respectively

• Storage capacity in the dry season is reduced by 3.6% (493m3

daily)• Power production in the dry

season is reduced by 3.5% (3,194kWh)

• Annual economical cost from power generation reduction is 462,000USD of which 83% of the loss occurs during the dry season

• However most of electricity is generated during the wet season. Dry season production is only 22% of the yearly production

-4.0%

-3.5%

-3.0%

-2.5%

-2.0%

-1.5%

-1.0%

-0.5%

0.0%

Annually Dry season Wet season

Ch

ange

(%

)Storage capacity Power generation

Conclusions of the water availability assessment

• Relatively small change for hydro power production (i.e. 1% energy reduction annually) can have big impact on communities surrounding Yali reservoir (within 2km). Especially in the dry season, when there is water stress and higher dependency on groundwater.

• 462,000USD loss from electricity production could bring greater benefit for surrounding community

Thank you!