The Effects of Escalating Small Hydropower Development on Hill Stream Fish Fauna Endemic to Sri Lanka

Abstract

Small hydropower (SHP) generation by arresting mountain streams is being viewed as environmentally benign energy source, compared with large dams and fuel fossils combustion as it has no effects on global climate change (Egrea & Milewski 2002). They can, however, exert multiple negative effects locally specially, on riverine and riparian ecosystems and eventually on aquatic biodiversity and human health of riparian communities, but reported studies on these aspects are hardly any (Bhushan et al. 2013). Ecological risk of cascade operation of SHPP established on the trunk stream poses adverse effects, as it leads to almost drying up of the natural river channels during dry season (Bhushanet al. 2013, Silva et al. 2013) whereas MHPPs affect not only fish but also ecological integrity of lotic ecosystems. Apparently, present knowledge and findings have fueled that principles of ecosystem science need to be fully integrated into water resources planning and management (Poff 2009). Unfortunately, these aspects have been totally ignored by project approving agencies in developing countries when permissions are granted to establish and operate SHPPs on hill streams that are rich in endemism. Nevertheless, developing countries pose direct or indirect taboos or rigid environmental legislation discouraging entrepreneurs. If SHPPs are designed, constructed, monitored and managed stipulating correct norms, can minimize effects on the ecosystems and c some eco-friendly examples are there in the western world as well shown for ancient irrigation in Sri Lanka by Silva et al. (2014).

Sri Lanka has the SHP potential of about 400 MW and the government encouraged and facilitated private sector to undertake the development of SHP ventures with flexible power purchasing agreements as the country has already tapped almost every potential sites for large hydropower developments. A request was made by the Mahaweli Authority of Sri Lanka (MASL) to Water Resources Science and Technology (WRST) through International Water Management Institute (IWMI) to examine whether there is a significant impact of construction and operation of SHPPs on hill stream fish fauna. The preliminary results revealed that the construction and operation of seven MHPPs within 23 km stretch on Sudu Ganga (=River) in the Mahaweli River basin has significant negative impacts on fish fauna (Silva et al., 2013). As Sri Lanka is identified as a biodiversity hotspot with rich endemic ichthyofauna, confined to hill streams, the study was extended to headwater streams of the entire country with a grant awarded by Asia Pacific Network for Climate Change Research (APN). Therefore, the study was focused to collate necessary information to determine the gravity of poorly designed and scientifically unsound construction and operation of small hydropower plants on ichthyofauna endemic to Sri Lanka with a view to transferring knowledge on the significance of maintaining ecological flow in streams and rivers to sustain aquatic biodiversity evolved for millions of years.

Necessary data were collected from relevant government institutes (viz., Sustainable Energy Authority, Central Environmental Authority, Ceylon Electricity Board, Public Utility Commission of Sri Lanka and Mahaweli Authority of Sri Lanka). Field visits were made to 61 SHPPs in the Mahaweli River basin and an extensive study was conducted on five SHPPs (physical structures and operations) established on Wee Oya (= Stream) in Kelani River basin, which also included fish sampling. Google Pro images were used for validation of geographic positions and estimation of stream lengths between the weir and the powerhouse (ASS= Affected Stream Stretch) along 25 km stream stretch in Wee Oya and other MHPPs.
The development of MHP was commenced in 1993 and 142 plants generating 302 MW were connected to the national grid by the end of 2014 while another 37 plants are under construction. Although plant designs indicate projects as run-of-river systems, none of the visited projects did not maintain environmental flow between the weir and powerhouse creating dead stream stretches unless lateral tributary inputs are available. ASS of Wee Oya was estimated as 7.2 km for 24 km stream stretch, which includes five MHPPs whereas AAS was 340 km for 142 MHPPs that are in operation in the central highlands.The number of hill stream fishes in Sri Lanka is 50 belonging to eleven families of which 35 are endemic. Of the endemic fishes, 26 are found only hill streams between 100 -1000 m amsl where their type habitats are located. Fourteen endemic fishes restricted to hill streams have been recorded from the Kelani River of which ten species were found in Wee Oya before the construction of the first MHPP in 2005. The present study found only three endemic fishes restricted to hill streams where water is brought to the mainstream from lateral tributaries. The results demonstrate devastating effects of inappropriate construction and incorrect operation of MHPPs on stream habitats and ichthyofauna endemic to Sri Lanka as reported at several occasions (Silva and Davies 1986, Silva 1993, Arthington et al. 2006, Poff 2009, Bhushan et al. 2013, Silva et al. 2013). This situation is worse than the operation of large hydropower with respect to the extent of ASSs. The effects of exposed stream beds on ecological integrity and human health of riparian communities are to be investigated.

Full text

The effects of escalating small hydropower development on
hill stream fish fauna endemic to Sri Lanka
E.I.L. Silva, E.N.S. Silva
Water Resource Science and Technology
77/2, Hettiyawatte,
Elapitiwela,
Ragama
Sri Lanka
R.A.S.N. Jayawardhana, N.P.P Liyanage
Department of Animal Science
Uva Wellassa University
Badulla
Sri Lanka
Introduction
Small hydropower (SHP) generation by arresting mountain streams is viewed as environmentally benign energy
source, compared with large dams and fuel fossils combustion as it does not emit greenhouse gases (GHGs) (Egrea
& Milewski 2002). They can, however, exert multiple negative effects locally especially, on riverine and riparian
ecosystems, eventually on aquatic biodiversity and human health of riparian communities, but reported studies on
these aspects are hardly any (Bhushan et al. 2013). Ecological risk of cascade operation of SHP established on the
trunk stream poses adverse effects, as it leads to almost drying up of the natural river channels during dry season
(Bhushan et al. 2013, Silva et al. 2013, 2015) whereas SHP schemes affect not only fish but also ecological integrity
of lotic ecosystems. Unfortunately, these aspects have been totally ignored by project approving agencies in
developing countries when permissions are granted to construct and operate SHP on hill streams that are rich in
endemism.
The history of harnessing SHP in Sri Lanka dates back to the British colonial era, during which hydropower was
used as the main source of energy in large tea factories located in the hilly terrain of the central highland. After the
World War II, the relative advantage of SHP rapidly declined to owe to the installation of large-scale storage-type
hydro schemes, which began to supply the first stages of a national grid. Most of the major hydro potentials in Sri
Lanka were tapped by mid-1990s and hydropower happened to be the largest contributor of power generation of the
country. Nevertheless, unavailability of potential sites for major hydropower development, associated inflation and
high labor cost and environmental issues has led to exploring the potential of small hydropower in the country. Sri
Lanka has the SHP potential of about 400 MW (WSHDR 2013) and the government encouraged and facilitated
private sector to undertake the development of SHP ventures with flexible power purchasing agreements as the
country has already tapped almost every potential sites for large hydropower development. To generate hydropower,
weirs to be constructed across streams, divert water to send through generators and release water back to the stream.
This process is not very favourable for healthy stream ecosystems. Hill streams in Sri Lanka are type habitats for
much endemic fish and the country has categorized as a biodiversity hotspot because its rich endemic fauna
including fishes. Besides, Sri Lanka has stringent environmental rules and regulations adopted for the conservation
of biodiversity. The National Environmental Act enacted in 1988 introduced environmental clearance process prior
to the establishment of “Prescribed Projects” that are likely to have significant impacts on the environment. Power
generation and transmission are listed as prescribed projects. In order to understand the sustainability of two
compulsory but conflicting policies, this study was conducted on the status of progressive SHP development and
endemic fish fauna in Sri Lanka.
1.0 Background
A request was made by the Mahaweli Authority of Sri Lanka (MASL) to Water Resources Science and Technology
(WRST) through International Water Management Institute (IWMI) to examine whether there is a significant impact
of construction and operation of SHP on hill stream fish fauna. The study was primarily focused on headwater
stream networks of Mahaweli and Walawe Rivers under the purview of MASL and their associated flow-regulatory
structures with special emphasis on small hydropower schemes in order to highlight the present status of freshwater
fish fauna, native and endemic to Sri Lanka. Besides, more emphasis was paid on the mini-hydropower plants that
are already connected to the national grid; those are at different construction stages and sites that have been
approved for the construction. At each site, topographical features (coordinates, elevations, slopes, river bottom

features etc,) were recorded in addition to the distance between the weir and the powerhouse, the stream stretch that
could be adversely affected (ASS = Affected Stream Stretch). The aforesaid features were compared with recent
satellite images of Google Earth-Pro and 1:50,000 topographic sheets for comparison. Further, observations were
made on fish fauna and the information on fish inhabiting the stream stretch was gathered from the people living in
the area whenever it is possible. Desk studies were carried out to collect the physical features, flow-regulatory
structures and the details of project designs in relation to environmental aspects in the case of mini-hydropower
plants. The study was further extended to examine the headwater streams networks several other rivers (i.e., Kelani,
Kalu, Gin and Nilwala) of the country with the help of a grant awarded to the WRST by Asia-Pacific Network for
Global Change Research (APN) and research students allocated by the Uva Wellassa University.
2.0 Small hydropower in Sri Lanka
The geo-climatic settings of Sri Lanka are particularly conducive to harnessing hydro resources: a highland mass in
the south-centre, surrounded by an intermediate zone of upland ridges and valleys lying at the lower elevation.
Prevailing climate of Sri Lanka is largely determined by the meteorological conditions caused in the Indian sub-
continent due to tropical monsoon. Two contrasting wing regimes formed as a result of the Asian monsoons is the
major phenomenon caused by these conditions. The southwest monsoon prevails from May to September and the
northeast monsoon occurs from December to February. These are responsible for the distinct seasonal rainfall in Sri
Lanka. Nevertheless, orographic nature of the Central Highlands of the island is decisive on rainfall intensity and
distribution. Given the humid conditions and the hilly terrain, the highlands of Sri Lanka offer excellent
opportunities to harness hydropower for the generation of electricity.
2.1 SHP in major river basins
Although the terrain of Sri Lanka has been divided into 103 drainage basins only ten rivers rise from the Central
Highlands in the wet zone (e.g., Mahaweli, Maha, Kelani, Kalu, Gin, Nilawala, Walawe. and Kirindi). The
Mahaweli River, the longest and the largest river basin of the island has 57 mini-hydropower plants with 113 MW
generation capacities in operation while another few are under construction (Figure 1 & Table 1). Establishment of
mini-hydropower plants has disrupted 77.3 km long stream stretches due to non-availability of stream flow between
the weir and powerhouse of each SMP plant. The total affected (disrupted) stream stretches (ASS) within the
Mahaweli basin were estimated as 77.3 kilometers while generating 113 MW. In contrast, loss of stream stretches
due to major hydropower schemes (i.e., Upper Kotmale, Kotmale, Victoria, and Randenigala-Rantambe) on
Mahaweli River is 33.3 km, which generates 810 MW. Thirty-two mini hydropower plants with 55.61 MW
generation capacities are in operation on the Kelani River basin creating 47.3 km dead stream stretches (Table 1)...
In addition, the affected stream stretch resulting from five major hydropower schemes (i.e., Wilmasurendra, Old
Lakshapana, Canyon, New Lakshapana and Polpitiya) is 41.9 km while generating 353MW.
In the case of Kalu Ganga (= River), twenty-eight mini-hydropower plants of 70MW generation capacity are in
operation at present resulting in the disruption of 20.8 km stream habitats whereas, the Walawe Ganga has
fourteen mini-hydropower plants having 26.84MW generation capacity. These MHP plants have also resulted in
creating dead stream stretches of 17.3 km but there is no dead stream stretch at the immediate downstream of the
major hydropower reservoir (Samanalawewa) as there is a continuous downstream flow due the permanent leakage
of water through the dam. Twelve MHPs are in operation in the other river basins (Gin Ganga, Kirindi Oya, Maha
Oya Maduru Oya and Nilwala Ganga); by the end of 2014 generating 21.95MW but the disrupted stream stretch is
about 9.4 km because some MHP plants located on existing dams and irrigation canals. Accordingly, construction
and operation of 143 small hydropower schemes on hill streams in the Central Highland of Sri Lanka since early
1990 to 2015 has resulted in stream water to flow 225 km through conduits, concrete canals, penstocks, and
tailraces disrupting downstream flow and sediment transport, seepage and recharge, in turn, evolutionarily
established biogeochemical clots and e hydrological network. This has significant effects on riverine endemic fishes,
stream bank vegetation and the livelihood of riparian communities. Nevertheless, authorities have granted
permission for permission have granted for another 87 projects with installation capacity of about 139MW.

Table 1: Number of mini hydropower plants, their installation capacity, and estimated stream lost in different sub-
watersheds of the Mahaweli River basin
3.0 Hill stream fishes
The number of freshwater fish species native and endemic to Sri Lanka has changed vigorously over the last two
decades. According to the latest publication on freshwater fishes in Sri Lanka (DE Silva et al. 2015), about 93
species belonging to 22 families, with 47 cyprinids (Family: Cyprinidae) that need freshwater habitats to complete
their life-cycle have reported from Sri Lanka. Of the 93 freshwater fishes, about 54 are endemic of which 41 are
confined to the hill streams of the wet zone of the country with distinct biogeographic distribution (Table 2)..
Fourteen species of endemic species inhabiting hill streams are critically endangered while thirteen are endangered
according to IUCN Red Data List. Only three endemic fish species inhabiting hill streams are near threatened and
the same number is vulnerable (Table 2). Although described as new species endemic to Sri Lanka during the recent
past, the status of six fish species have not been evaluated yet by the International Union for Conservation of Nature
(IUCN) and specimen are not available in the National Museum. Most of the endemic species are extremely rare
and restricted to the particular biogeographic region. Critically endangered species found in Knuckles cannot be
found either in Central Mahaweli Hills or other biogeographic regions (e.g., Kelani, Kalu, Gin, Nilawala and
Walawe). The highest number of endemic species has been reported from Kelani, Kalu, and Gin Biogeographic
Regions while the number of endemics is relatively low in Central Mahaweli Hills and Walawe Biogeographic
regions.
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

River Basin Number of Plants Installation
Ca
p
acit
y
(MW) Affected Stream
Stretch (km)
Mahaweli 57 113.4 77.3
Kelani 32 55.61
47.34
Kalu 28 69.91 20.82
Walawe 14 26.84 17.31
Gin 02 3.95 0.80
Nilawala 03 1.10 0.60
Kirindi Oya 02 1.40 0.40
Maa Oya 03 7..50 4.30
Maduru Oya 02 7.00 00.0
Total 143 279.2 168.9

Fig. 1. S
c
s
tructure
s
c
hematic diag
r
s
r
am of Maha
w
w
eli
R
iver bas
i
i
n depicting s
i
i
tes for mini-
hy
hy
dropower pl
a
a
nts and othe
r

r
regulatory


Fig. 2.
P
P
resent distrib
u
u
tion of majo
r
r
hydro and mini-hydropow
e
e
r plants in S
r
r
i Lanka

Table 2: IUCN status of endemic fishes inhabiting hill streams in Sri Lanka with their biogeographic distribution in
seven Biogeographic Regions; 1. Knuckles (KN); 2. Central Mahaweli Hills (MW); 3, Kelani (KL); 4. Kalu (KL); 5.
Gin (GN); 6. Nilwala (NL), and 7.Walawe (WL);
IUCN Status Number
of species Number of
Families Biogeographic Region
NK MW KL KL GN NL WL
Critically endangered (CR) 14 04 04 01 01 02 03 02 01
Endangered (EN) 13 06 01 01 11 08 07 06 02
Near threatened (NT) 03 03 03 03 03 03 03 03 03
Vulnerable (VU) 03 02 01 02 01 02 01 02 01
Least concerned (LC) 01 01 01 01 01 01 01 01 01
Not evaluated (NE) 06 01 01 01 00 01 03 00 01
Data Deficient (DD) 01 01 01 00 00 00 00 00 00
Total 41 09 11 08 17 17 17 14 09
4.0 Discussion
The overall picture of mini-hydropower distribution in Sri Lanka is amazing (Figure 2). The entire hydrological
network of the Central Highland has dramatically changed over the last two decades. The Government of Sri Lanka
still did not realize the gravity of the problem with respect to ecohydrology of the mountain landscape, which also
provides many services in addition to cash crops production. It is well-known that the mountain landscape of the
island is the water tower, which supplies water to the other parts of the island via surface run-off and underground
flow. Besides, the natural hydrological network plays a vital role shaping the entire landscape features including its
flora and fauna. The devastating disruption of natural system at unwarranted magnitude may lead to unprecedented
consequences. Therefore, it is extremely important to pay equitable consideration on the environment not in a
superficial manner for the sake of doing but in realistic and in-depth ecological and geomorphologic understanding.
Freshwater fishes in Asian rivers are susceptible to the anthropogenic threats resulting from deforestation,
infrastructure development, streamflow regulation, diffused and point-source pollution and over-exploitation
(Dudgeon 2000). The situation in Sri Lanka is also similar with several exceptions (e.g., urbanization, gem-mining,
over-use of pesticides, ornamental fish trade, use of destructive fishing methods and introduction exotic fish) as
reported by several authors (Senanayake and Moyle 1982, Wijeyaratne 1993, Pethiyagoda 1994, 2006, Gunasekara
1996, Bambaradeniya 2002). Most of these factors are interrelated with each other, but habitat degradation and
impairment of water quality are among the main decisive factors attributable to population decline and gradual
extinction. Fish species inhabiting agricultural watersheds are eco-physiologically substandard compared to their
counterparts found in forested watersheds (Jayakody et al. 2011). Further, the negative effects of large dams on
riverine fish fauna have been discussed in detailed in many instances (Silva 1993, Arthington et al. 2006, Poff 2009,
Bhushan et al. 2013).Marked decline in two species of migratory eels native to Sri Lanka was observed following
the construction of five trunk stream dams on the Mahaweli River (Silva 1993). The effects of a cascade of small
hydro dams on Sudu Ganga (a major tributary of Amban Ganga) in Matale District (Silva et al.2013) and on Wee
Oya in the Kelani River basin (Silva et al. 2015) were highlighted and devastating negative effects of inappropriate
and incorrect construction and operation of mini hydropower plants on fish fauna endemic to Sri Lanka were well
addressed.
The results of the present study are evident for a clear-cut site-specific distribution of hill stream endemic fishes in
Sri Lanka which is more elucidated compared to the previously described zoogeographic distribution of freshwater
fishes into three regions (Mahaweli, Dry Zone, and Southwest Wet Zone) by Senanayake (1985). The availability of

the highest number of endemic fishes in the headwaters of Kelani, Kalu, and Nilwala may be attributed to habitat
availability whereas the lowest number of endemics in the Central Mahaweli Hills has resulted certainly from long-
term habitat alteration. Apparently more type habitats are available in the headwaters of Nilwala River compared
with the foothills of Knuckles but the least number of endemic fishes in the Walawe River basin may be attributed to
non-availability of type habitats to thrive fish owing to its peculiar geomorphologic features of the landscape. No
wonder, the only critically endangered endemic fish in the Central Mahaweli Hills, Pethia bandula may disappear
from its type habitats in the near future due to the high density of mini-hydropower plants. Likewise, there is a
possibility that other critically endangered species will disappear from their respective river basins. For example,
Malpulutta kretseri from Kalu Ganga basin, and Laubuca varuna from Walawe River basin, have only one critically
endangered species. As evident from the biology of cyprinids in hill streams in Sri Lanka, most of the endemic
freshwater fish species tend to show well-defined niche segregation and ecological adaptations (Shirantha 2004).
Environmental clearance through IEE/EIC process is mandatory for the establishment of mini-hydropower projects
in Sri Lanka. It is crystal clear that endemic fishes either critically endangered or endangered inhabit hill stream but
IEE/EIA reports which are heavily loaded on carbon trade hardly address the issue on endemic fishes and none of
these small power generation schemes are implemented mitigation measures to conserve fish fauna. As shown by
Silva et al. (2015) stream regulation in Sri Lanka under ancient hydraulic civilization was much more environment-
friendly than modern systems that should be taken into consideration by modern engineering developments.
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Authors
Prof E.I.L. Silva: Chairman/Chief Executive officer of Water Resources Science and Technology, awarded his
doctoral degree from the University of Calgary, Canada was the former Director General of the Ocean University of
Sri Lankan and the National Aquaculture Development Authority of Sri Lanka.
P.P. Liyanage: Lecturer at the Department of Animal Science of the Uva Wellassa University of Sri Lanka obtained
his B. Sc. special degree in zoology and Master of Philosophy degree in Fish Genetics from the Ruhuna University
of Sri Lanka.
R.A.S.N. Jayawardhana and E.N.S. Silva: Both are final year undergraduate students following the special degree
in Aquatic Resources Technology at the Department of animal Science of the Uva Wellassa University, Sri Lanka.