Section 11.2.ii states that the simulation "will calculate
downstream effects of the" various reservoir discharge scenarios.
No further discussion or details are provided regarding this claim.
It is not clear how the simulation model could calculate downstream
effects, beyond rough estimates of streamflow.
Section 11.2.iv states that "secondary hydropower generation
is calculated and sold to the Republic of South Africa. The price
for sold energy is assumed to be 75% of the import price."
This assumption is used in the simulation model to estimate benefits
of the Epupa Project, but it is not clear if South Africa would
consider purchasing power from Namibia because the RSA has a surplus
of generating capacity.
Section 11.3.2.1 states that the consultants extended the simulations
to the year 2050. The Epupa Project would have been operating
for approximately 45 years by that time, yet the simulation model
does not account for the inevitable rise in operation and maintenance
costs the Epupa Project will experience by that time. A study
of several hundred North American hydrodams shows that, on average,
hydrodam operating costs rise dramatically after approximately
30 years.1 Long-term estimates of project benefits
should reflect this fact.
Section 11.3.2.3 discusses the value of energy that is not supplied
to the customers due to temporary shutdowns, drought etc. It states
ìthe cost for unserved energy is normally in the range
of 0.25 - 5.0 USD, depending on the infra-structure and industrial
development level of a country." The study explains that
one consequence of high unserved energy costs is that unreliable
generation plants are economically penalised. The section goes
on to describe that because "the Namibian economy is highly
dependent on electricity dependent industries", the cost
of unserved energy should be set relatively high. Yet the cost
is set at 1.5 USD, which is in the lower one-third of the range
of costs. The consultant unjustifiably chose a lower unserved
energy cost, which would protect the Epupa Project from economic
penalties resulting from the degree of unreliability of Epupa’s
generation.
Section 11.3.2.4 discusses the hydrological data used in the simulations,
arguably one of the most important components in hydrodam modelling.
This section is misleading and extremely vague. It does not describe
the streamflow values used, nor does it adequately describe the
rationale for choosing them. Without knowing the assumptions used
for this component, it is impossible to know if the analysis is
reasonable or accurate. The study states that "the last 49
years of streamflow data for the Cunene are used." This is
either a misstatement or a gross error in the simulation methodology.
Chapter 7 of the Feasibility Study, "Hydrology", explains
in detail why the Cunene streamflow record is unusable for modelling
purposes except for a period of 12 years (1961-72). Streamflow
data for all but these 12 years had to be generated, creating
a synthesised data set. Thus, the simulations are based not on
empirical streamflow data as is suggested in this section, but
on synthetic data. This is an important point because such synthesised
data sets have been shown routinely to overestimate future streamflow
and exaggerate project benefits.2
Section 11.5.1.1 summarises the technical and economic aspects
of the project. The section lists evaporation at 1,765 mm per
year, which does not agree with the 1,890 mm per year figure listed
in Table 7.10.4 on page 7-63 of the Hydrology chapter. The 1,765
mm figure underestimates evaporation by approximately 7%, which
is more than 40 million cubic meters per year.
Section 11.5.2.1 discusses the ability of Epupa and Ruacana to
eliminate the need to purchase power from RSA. The picture presented
here conflicts with the discussion in Chapter 13, "Epupa
Reservoir", which states "Simulation runs presented
here indicate that retaining ample storage volumes at the end
of dry seasons and compensating the energy shortage thus incurred
by import, will result in increased loss of water over the spillway
and consequently decreased energy production in the long run."
(Emphasis added). Thus, while Epupa and Ruacana together might,
in theory, be able to almost eliminate the need to import power,
it seems clear that the project likely will be operated in such
a manner that Namibia will still be required to import significant
amounts of energy, particularly during the months at the end of
the dry season before streamflows increase.
Footnotes
1 T. Wong, "Determining O&M
Costs Over the Life of a Hydro Station", in Hydro in the
90’s, Hydro Review World-wide, Kansas City 1994.
2 The greatly overestimated streamflow estimates
for Phase 2 of the Lesotho Highlands Water Project represents
only one of the most recent examples.
Steve Rothert
International Rivers
PO Box 2427
Gaborone, Botswana
E-Mail: stever [at] info [dot] bw
Further Reviews:
- Commentary on the Environmental Assessment Report of the Feasibility Study on the Proposed Lower Cunene Hydropower Scheme, by Sid Harring
- A Review of the Epupa Draft Feasibility Study, by Steve Rivkin
- Comments on the Epupa Hydropower Project Feasibility Study, by Jamal Gore
- Epupa Dam and Reservoir Options - A Review of the Aquatic Ecological Aspects of the Draft Feasibility Report, by Kate Snaddon
- A Review of Hydrological Aspects of the Proposed Epupa Dam and Reservoir, Cunene River, Namibia, by Peter Willing
- A Review of Chapter 11, "Simulations", of the Feasibility Study for the Epupa Hydropower Scheme, Cunene River, Namibia, by Steve Rothert
- COMMENTS ON THE EPUPA DRAFT FEASIBILITY STUDY, by Hans Eggers
