1. QUANTIFYING WATER USER TRADE OFFS AT YALI
RESERVOIR
Bamboo 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

2. Contents
Characteristics
of water use
demand
Hydrological
Characteristics
Cost and benefit
evaluations
between water
users
• CIEM carried out
the survey within
2km buffer of Yali
reservoir
• Surface water
availability
• Reservoir water
allocation & flows
• Storage capacity
and hydro-
electricity
production
• Economic costs &
benefits
• Social costs and
benefits
• Conclusion

3. 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?

4. Water consumption
Item
Water 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

5. Overview of the methodology
_
Water
availability
Water
demand
Water
availability
with
consumptive
use
Identify
critical areas
Rainfall
Inflow
Water
demand
Evaporation
_
+ _ Outflow
Power
Production

6. Surface water availability:
Moisture budget without consumptive use

7. Surface water availability: with
consumptive use

8. Water availability in the dry season

9. 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?

10. 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

11. 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
Energy(KWh)
LiveStorageCapacity(1000m3)
Reservoir storage Power generation

12. 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
Waterdemand(m3)

13. -20%
-18%
-16%
-14%
-12%
-10%
-8%
-6%
-4%
-2%
0%
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Change
Reservoir storage Power generation
Scenario 2 compared to Baseline
Wet season

14. 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
Change(%)
Storage capacity Power generation

15. 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

16. Thank you!