Initial Environmental Evaluation of Alternative Methods to Conserve Rupa Tal Lake, Nepal
Christopher M. R. Pastakia & Jesper Bay
(reprinted from Environmental Impact Assessment using the Rapid Impact
Assessment Matrix (RIAM)) ed. Kurt Jensen. Olsen & Olsen, Fredensborg,
Denmark. 1998)
Abstract The paper describes an Initial Environmental
Evaluation (IEE) that was undertaken to assess the various alternative
interventions that might be carried out to conserve or improve the existing
lake and valley of Rupa Tal,Nepal. The project was undertaken in a short field
visit, which allowed a reconnaissance of the area and direct discussions for
the views and experiences of local people. This data was analysed using the
Rapid Impact Assessment Matrix (RIAM) which allowed a sound basis for
comparison of alternatives.
Four alternative options were considered: a no action situation which
would result in complete sedimentation of the lake save for a central river
channel; a high dam on the southern margin to raise and maintain the water
levels above the existing level; a shorter, high dam within the existing lake
area with the same objective as the previous option; and a large sediment dam
or series of sediment-holding cascades to prevent sedimentation of the remaining
body of the lake.
The IEE was able to define a series of important components for
comparison of these options, and the RIAM demonstrated the variation in impact
that each option would produce. The IEE shows that the RIAM is an effective and
rapid method to arrive at holistic comparison of strategic options in planning.
From the RIAM results it has been possible to show that the mid-lake dam
provides little additional benefit to the southern margin dam. The latter has a
number of negative sociological and economic/operational impacts, but also
significant positive benefits. A detailed in-depth EIA would be needed before
proceeding with this option.
The option of providing up-stream sedimentation was shown to be the least
disruptive option, though with negative impacts in operational and maintenance
costs and implementation. This was the most likely option to maintain the
present shape and form of the lake.
Introduction Rupa Tal (the Lake
of Beauty) lies in the Begnash and Rupa Lakes watershed area in the north-east
of Kaski District in the midwestern region of Nepal. This area is about 150 km
west of Kathmandu, within the co-ordinates: latitude 28°7N to 82°12N and
longitude 84°5E to 84°10E.
At present Rupa Tal is undergoing sedimentation at a rapid rate, with the
lake area being reduced from 194 ha to 115 ha between 1978 and 1995 (a loss of
40% in 17 years) (Oli, 1996). The present lake basin continues to receive
sediments from the receiving streams to the northeast. The lake is fed from an
upland stream (Dobhan Khola), and drains to the south through a small
meandering channel (Tal Khola) to the Seti River. The southern margin of the
lake has become a small marginal marsh, which drains the southern agricultural
lands into the lake before entering the Tal Khola. In addition to these
geo-physical changes, the present lake is highly eutrophic, with a considerable
biomass of sub-surface and emergent macrophytes. It is probable that the
deposition of weed peat will accelerate the sedimentation of the present lake
area. Figure 1 gives a diagrammatic view of Rupa Tal and the existing areas
affected by sedimentation.
Possible
interventions Rupa Tal has traditionally been a major internal tourism area, and the
local authorities are anxious that the beauty of the lake and its valley are
preserved. The surrounding hills have been terraced along the lower slopes for
rice production, and cropping now also occurs on the sedimented areas of the
lake. To the south rice cultivation is dominant. The lake body provides a small
degree of fishery income, including rudimentary cage aquaculture. The local
authorities consider the rate of lake sedimentation to be an adverse phenomenon
in respect of the preservation of the lake and the valley; and accordingly wish
to consider possible interventions that might conserve a lake area and preserve
the valley for tourism, agriculture and fisheries, as has been done elsewhere
in this region of Nepal (NPC, 1995).
Four possible forms of action can be considered for the future
possibilities in respect of the conservation of the lake area:
1.
No action, allowing the present sedimentation to continue, resulting in
total loss of the lake, and the
creation of a small gorge to take the inflow/outflow streams.
2.
Building a high retaining dam along the southern margin to raise the
overall water level (Figure 1: A-AA). This would be a major structure, and
would inundate in-lake areas that have been created by sedimentation over the
last few decades.
3.
Building a smaller, high dam set between two bluffs, about one third of
the way up from the southern shore (Figure 1: B-BB). This partial dam would be
a smaller construction than (2) but would have similar upstream effects.
4.
Either a single large sedimentation reservoir in the upstream area, or a
series of smaller retaining walls, forming a sedimentation cascade (Figure 1:
C-CC). This option allows solids to settle out well upstream of the present
lake, and the present water area then will be able to remain intact.
Initial environmental
evaluation To assist in the evaluation of these alternative options, the authors
made a short three-day visit to Rupa Tal, and an initial environmental
evaluation (IEE) was undertaken, using the Rapid Impact Assessment Matrix
(RIAM).
Scoping was undertaken after a reconnaissance of the lake environments
and observation of possible environmental problems related to changes in
sedimentation. Local opinions were included in the scoping exercise, through
discussions with the local people, members of the Village Development Council,
and members and ex-members of the local authority and planning bodies.
The scoping exercise considered aspects of all four parts of an holistic
environmental impact assessment: physical/chemical (P/C); biological/ecological
(B/E); sociological/cultural (S/C); and economic/operational (E/O). Due the
rapidity of the exercise and the need to make comparative evaluations in the
absence of quantitative data, the final impact assessment is considered to an
initial environmental evaluation (IEE) rather than a full environmental impact
assessment (EIA).
The components chosen by the scoping exercise were used to compare the
perceived impacts for all four development options defined above. These
components are set out in Table 1.
Figure 1. Plan of Rupa Tal (not to scale)
Table 1. Rupa Tal. Selected
components for IEE by RIAM
Physical/Chemical
P/C 1 Changes in lake water volume
P/C 2 Changes in lake sedimentation (measure of reduction of water
surface)
P/C 3 Changes in crop and grazing areas
Biological/Ecological
B/E 1 Changes in lake fisheries
B/E 2 Changes in biodiversity
B/E 3 Changes in primary production
B/E 4 Changes in aquatic macrophytes
B/E 5 Changes in disease vector populations
Sociological/Cultural
S/C 1 Loss of housing
S/C 2 Loss of shops/public buildings
S/C 3 Changes to access routes
S/C 4 Changes induced by changes in tourism patterns
S/C 5 Changes to water supplies
S/C 6 Changes to diet/nutrition
S/C 7 Changes to aesthetic landscapes
S/C 8 Changes in water/vector borne disease
S/C 9 Changes to upstream quality of life
S/C 10 Changes to downstream quality of life
Economic/Operational
E/O 1 Changes in crop-generated incomes
E/O 2 Changes in fishery generated incomes
E/O 3 Ease of Operation & Maintenance of option
E/O 4 Cost of Operation & Maintenance of option
E/O 5 Cost of resettlement/compensation for land loss
E/O 6 Cost of rehabilitation/restoration of shops/public buildings
E/O 7 Cost of restoration of access routes
E/O 8 Changes in tourism-generated incomes
The physical/chemical components were restricted to those that related to
the changes in lake water volume and the processes of sedimentation, with the
concomitant changes in agricultural land that each option might cause.
Biological/ecological components reflected changes that might occur with
each option in respect of the biota in the lake, specifically primary
production, the change in aquatic macrophytes (secondary production) and
finally changes in lake fisheries (including its ability to support
aquaculture). In addition, the biodiversity of the southern margin marsh and
the changes in insect disease vector populations were considered.
In considering the sociological/cultural components it was evident that
each option provided different results to the present human settlement pattern
of the area. Sedimentation has provided new land both for agriculture as well
as houses and public buildings. Shops, temples and a school have been developed
within the sedimented areas of the lake, and housing is found both in these
areas as well as along the margins and higher reaches of the shores. This
dwelling and development pattern has set the access routes to the area and
these too would be affected by some options. The biological changes would have
an impact on both diet and disease, and these two components are included. The
aesthetic value of any option relates to tourism attractiveness, and this
component together with an evaluation in the change in quality of life of the
local communities completes this group.
The economic/operational components reflect the changes in agricultural,
fishery and tourism incomes that might be expected from each option. The cost
of mitigation in the form of rehabilitation of buildings and access routes is
considered. Both the cost and complexity of the operations and maintenance of
each option have been included in this group.
To complete the IEE, these components were evaluated using the Rapid
Impact Assessment Matrix (RIAM). In this instance the RIAM used the following
assessment criteria: Importance (A1), Magnitude (A2), Permanence (B1),
Reversibility (B2) and Cumulation (B3). The results of the RIAM are set out in
Table 2 for all the four options, and the final range values obtained from
these results are summarised in Table 3 and Figure 2.
Table 2. Rupa Tal. RIAM
results for each development option.
Option no. 1. No development
Evaluation Range
Values ascribed to RIAM criteria Score, Value
A1 A2 B1
B2 B3 ES RV
P/C 1 1 -3 3
3 1 _21 _C
P/C 2 1 _2 3 3
1 _14 _B
P/C 3 2 2 3
3 1 28 C
B/E 1 1 _2 3 3
3 _18 _B
B/E 2 1 _2 3 3
3 _18 _B
B/E 3 1 _2 3 3
3 _18 _B
B/E 4 1 _2 3 3
1 _14 _B
B/E 5 1 1 3
3 3 9 A
S/C 1 1 0 1
1 1 0 N
S/C 2 1 0 1
1 1 0 N
S/C 3 1 1 3
2 1 6 A
S/C 4 1 _1 3 2
1 _6 _A
S/C 5 1 _1 3 2
1 _6 _A
S/C 6 1 0 1
1 1 0 N
S/C 7 1 _2 3 3
1 _14 _B
S/C 8 1 1 3
2 3 8 A
S/C 9 1 0 1
1 1 0 N
S/C 10 1 _1 2 2
1 _5 _A
E/O 1 1 2 3
2 3 16 B
E/O 2 1 _2 3 3
1 _14 _B
E/O 3 1 0 1
1 1 0 N
E/O 4 1 0 1
1 1 0 N
E/O 5 1 0 1
1 1 0 N
E/O 6 1 0 1
1 1 0 N
E/O 7 1 0 1
1 1 0 N
E/O 8 1 _1 3 1
1 _5 _A
Option no. 2. High dam on southern margin
A1 A2 B1
B2 B3 ES RV
P/C 1 1 2 3
3 1 14 B
P/C 2 1 2 3
3 3 18 B
P/C 3 1 _2 3 3
1 _14 _B
B/E 1 2 2 3
3 3 36 D
B/E 2 1 _1 3 3
3 _9 _A
B/E 3 1 _2 3 3
3 _18 _B
B/E 4 1 _2 3 3
3 _18 _B
B/E 5 1 1 3
1 1 5 A
S/C 1 1 _1 3 1
1 _5 _A
S/C 2 1 _1 3 1
1 _5 _A
S/C 3 1 _1 3 1
1 _5 _A
S/C 4 1 2 3
2 1 12 B
S/C 5 2 2 3
1 1 20 C
S/C 6 1 1 3
1 1 5 A
S/C 7 1 2 3
3 1 14 B
S/C 8 1 _1 3 1
3 _7 _A
S/C 9 1 1 3
1 1 5 A
S/C 10 1 2 3
1 1 10 B
E/O 1 1 _1 3 1
1 _5 _A
E/O 2 1 2 3
2 1 12 B
E/O 3 1 _1 3 3
1 _7 _A
E/O 4 1 _1 3 3
1 _7 _A
E/O 5 1 _2 2 1
1 _8 _A
E/O 6 1 _1 2 1
1 _4 _A
E/O 7 1 _1 2 1
1 _4 _A
E/O 8 2 2 3
2 1 24 C
Option no. 3. High dam within existing lake
A1 A2 B1
B2 B3 ES RV
P/C 1 1 2 3
3 1 14 B
P/C 2 1 _1 3 3 3 _9 _A
P/C 3 1 0 3
1 1 0 N
B/E 1 1 1 3
3 3 9 A
B/E 2 1 _2 3 3
3 _18 _B
B/E 3 1 _1 3 3
3 _9 _A
B/E 4 1 _1 3 3
3 _9 _A
B/E 5 1 1 3
3 1 7 A
S/C 1 1 _1 3 1
1 _5 _A
S/C 2 1 _1 3 1
1 _5 _A
S/C 3 1 _1 3 1
1 _5 _A
S/C 4 2 1 3
2 1 6 A
S/C 5 1 1 3
2 1 6 A
S/C 6 1 1 3
2 1 6 A
S/C 7 1 1 3
3 1 7 A
S/C 8 1 1 3
3 1 7 A
S/C 9 1 1 3
3 1 7 A
S/C 10 1 2 3
3 1 14 B
E/O 1 1 2 3
1 1 10 B
E/O 2 1 0 3
1 1 0 N
E/O 3 1 _1 3 3
1 _5 _A
E/O 4 1 _1 3 3
1 _7 _A
E/O 5 1 _2 2 1
1 _8 _A
E/O 6 1 _1 2 1
1 _4 _A
E/O 7 1 _1 2 1
1 _4 _A
E/O 8 1 1 3
2 1 6 A
Option no. 4. Upstream sedimentation reservoir/cascades
A1 A2 B1
B2 B3 ES RV
P/C 1 1 0 3
1 1 0 N
P/C 2 1 2 3
3 3 18 B
P/C 3 1 0 1
1 1 0 N
B/E 1 1 0 1
1 1 0 N
B/E 2 1 0 1
1 1 0 N
B/E 3 1 0 1
1 1 0 N
B/E 4 1 0 1
1 1 0 N
B/E 5 1 _1 3 3
3 _9 _A
S/C 1 0 0 1
1 1 0 N
S/C 2 1 0 1
1 1 0 N
S/C 3 1 0 1
1 1 0 N
S/C 4 1 0 1
1 1 0 N
S/C 5 1 1 3
2 1 6 A
S/C 6 1 0 1
1 1 0 N
S/C 7 1 0 1
1 1 0 N
S/C 8 1 _1 3 1
1 _5 _A
S/C 9 1 _1 3 1
1 _5 _A
S/C 10 1 0
1 1 1 0 N
E/O 1 1 0 1
1 1 0 N
E/O 2 1 0 1
1 1 0 N
E/O 3 1 _2 3 1
3 _14 _B
E/O 4 1 _2 3 1
3 _14 _B
E/O 5 1 0 1
1 1 0 N
E/O 6 1 0 1
1 1 0 N
E/O 7 1 0 1
1 1 0 N
E/O 8 1 0 1
1 1 0 N
Table 3. Rupa Tal.
Comparison of RIAM results
Option no.1 Option no. 2 Option no. 3 Option no. 4
P/C 1 _C B B N
P/C 2 _B B _A B
P/C 3 C _B N N
B/E 1 _B D A N
B/E 2 _B _A _B N
B/E 3 _B _B _A N
B/E 4 _B _B _A N
B/E 5 A A A _A
S/C 1 N _A _A N
S/C 2 N _A _A N
S/C 3 A _A _A N
S/C 4 _A B A N
S/C 5 _A C A A
S/C 6 N A A N
S/C 7 _B B A N
S/C 8 A _A A _A
S/C 9 N A A _A
S/C 10 _A B B N
E/O 1 B _A B N
E/O 2 _B B N N
E/O 3 N _A _A _B
E/O 4 N _A _A _B
E/O 5 N _A _A N
E/O 6 N _A _A N
E/O 7 N _A _A N
E/O 8 _A C A N
Figure 2. Rupa Tal.΄Numbers of each range value achieved
using RIAM 
Conclusions The IEE shows that
the RIAM is an effective and rapid method to arrive at holistic comparison of
strategic options in planning. The RIAM results presented very different
project profiles for each option (Figure 2), from which it has been possible to
provide an early indication of the merits of the various choices.
For option no.1 the RIAM analysis showed the expected negative impact due
to complete sedimentation of the lake over time, with the commensurate
improvement in available agricultural land. Negative impacts were associated
with the deterioration in aesthetic value (the loss of the lake) and
consequential expected downturn in tourism and related income. Some negative
impact on water supplies was also suggested. Positive benefits were associated
with improvement in access (over new ground); loss of water borne and insect
disease vectors; and improvements in crop generated incomes.
Option no. 2 produced a very wide profile, and indicated the wide variety
of issues that a large marginal dam would generate. On the positive΄side
significant improvements were seen in respect of lake fisheries and incomes
therefrom; water supplies to all communities should
improve; as would tourism
revenues. Improvements were seen to the problem of water vectors (by
replacing a shallow, still water surface with a wave-creating deep lake), and
to tourism related issues. Some improvement to the quality of life of all
communities was expected in the longer term. Economic and operational factors,
which were seen to be generally, negative, with a high initial loss of housing,
public buildings and access. The conclusion for this option is that the very
positive benefits in meeting the objectives of lake improvement would need to
be set against the initial negative impact on local people, and the costs
associated with mitigation of these impacts; together with the continuous high
cost of the operations and maintenance requirements.
Option no. 3 would show some cost improvements over option no. 2, but
many of the larger positive benefits disappeared with this option, whilst the
negative issues remained.
In option no. 4, most negative impacts reflect the high cost of
operations and maintenance associated with clearing out and disposing of
sediments accumulated by this system. As the present lake and its environs
would be preserved, the status of the area and the communities dependent on it
would remain largely unaltered from the present day. This lack of significant
change has produced the largely neutral RIAM result.
The results of this rapid assessment provide useful guidance for possible
future actions. A do nothing situation will result in a complete loss of the
lake, possibly via a phase of increased marshland and river formation in a
relatively short period of time (if present sedimentation rates continue), and
the RIAM has shown the impacts that such a situation
will generate.
To maintain the lake, there are effectively two technical solutions,
represented by options no. 2 and 4. Option no. 3 has been discounted as a
result of this IEE, as it provide little improvement in benefits over
costs΄when set against option no. 2. If capital and running costs do not prove
to be a major impediment to development, there is much to recommend
option no. 2. This option will nevertheless produce many initial changes,
and a full EIA on this option would be needed to indicate the true scale of the
positive/negative impacts identified. Option no. 4 offers the least change from
the status quo, although the operational costs would need to be carefully
considered. In terms of both cost and disruption, this IEE
suggests that option no. 4 is the solution most likely to be affordable
and able to meet the objectives of preserving the character of Rupa Lake.
Acknowledgements The authors wish to
acknowledge the considerable assistance provided to this evaluation by Mr
Krishna Oli for his valuable background data on Rupa Tal, and for his help in
logistical support in the field; as well as the number of local people who
provided anecdotal information to assist in this assessment
References
NPC (National
Planning Commission), 1995. Guidelines for Phewa Lake Conservation.
National Planning Commission/IUCN-World Conservation Union, HMG Nepal,
Kathmandu.
Oli, K.P., 1996.
Conservation of the Mid-hills: Land use changes in Begnash and Rupa
Lake Watershed area, Nepal, 1978-1996, pers. comm., awaiting publication.