Chapter 1: introduction

7.7 Selected VEC Baseline Status

7.7.1 Surface Water Quality and Quantity

The water quality of the Tamor River is good as the river is still fairly pristine. As the area is still devoid of industrial activities, there is no discharge of industrial effluent into the river. However, water quality tests for the Tamor River have not been conducted as part of this assessment. Rural activities, including agriculture wastes, animal and human defecation, and surface run-off from the catchment area, are non-point sources of water pollution. Secondary sources of information indicate the following water quality parameters for Tamor river¹⁸: water temperature ranges between 16.0-19.0^oC, DO ranges between 9.7-10 ppm, pH ranges between 7.3-7.5, total hardness between 28.5-34.2 mg/l, and conductivity between 37.7-56.7 μs/cm. But, as open defecation was seen along the river banks, some level of microbiological contamination of the water is highly probable.

As noted in Chapter 4, three samples of Kabeli River water at the project site (upstream of the dam, downstream of the dam and the dewatered section) were analyzed to assess river water quality. The overall chemical water quality of the Kabeli River is good. There are no industries discharging effluents in the river directly. However, activities like open defecation and use of water for different domestic purposes like bathing and washing utensils are common among the settlements along the riverbank and the river water is likely affected by microbial contamination. The river water in the dry post- and pre-monsoon season (October through May) is clear with low or negligible suspended sediment load. The sediment load significantly increases during the monsoon season from June to October.

As also noted in Chapter 4, Kabeli River is one of the tributaries of Tamor River, which is one of the major rivers of the Sapta Koshi Basin. The contribution of the Kabeli River to Tamor River hydrology at the powerhouse site is about 25% of the average annual flow, but its contribution in the dry season flow (March to April) is nearly 30%. Dry month mean monthly flow of the Kabeli (refer Figure 4.3, Chapter 4) is estimated as follows: November (25.25 m3/s), December (16.18 m3/s), January (10.31 m3/s), February (8.63 m3/s), March (8.88 m3/s), April (13.30 m3/s) and May (31.63 m3/s). Similarly, dry month mean monthly flows of the Tamor River at powerhouse site are estimated as follows: November (81.9 m3/s) December (52.5m3/s), January (39.1m3/s), February (32.3m3/s), March (31.4m3/s), April (45.2 m3/s) and May (96.2 m3/s).

7.7.2 Landslides/erosion and sedimentation

The Himalayas are young, rapidly uplifting, and eroding at one of the highest rates in the world. Combined with steep slopes, present and past glaciation, high rainfall intensities due to the monsoon, and sparse vegetative cover, the Himalayas have high erosion rates and the rivers witness high sediment transport rates in all five physiographic regions (see Table 7.6) of Nepal. The Greater Himalayas are sparsely populated and human impacts there affect erosion rates to a lesser extent. These regions are still covered extensively by glaciers that supply downstream regions with large inputs of sediments. Human activity often exacerbates and accelerates natural processes of erosion, and its potential impacts have been the central tenet of the Theory of Himalayan degradation. While the deleterious impacts of road building, vegetation removal, and soil compaction through agriculture may be self-evident, there have been few studies to quantify the hypothesized increase in erosion due to such activities. Despite documentation of road construction increasing erosion rates, there is no quantitative estimate of how much more sediment is contributed to the catchment from the increased landslides caused by road building (Heimsath 2005).

Table 7.6: Physiographic Regions of Nepal and their general characteristics

The Tamor basin is located primarily in the four regions – High Himalaya, High and Middle Mountains, and the Siwaliks. Given the typical characteristics of Himalayan terrain, there is natural risk of landslide and erosion in the Tamor basin because of the steepness of the slopes, the ruggedness of the terrain and the fragile and complex geology of fault lines, combined with heavy rainfall during monsoon. Geomorphologically, the Tamor basin is still in the formative process. The steep mountain slopes, particularly the valley slopes and the upper middle hillslopes, reflect the geomorphic dynamism of the area related to the mountain building tectonic activities. The general topographic forms reveal periods of active tectonism and tectonic quiescence. The two and three level terraces in the Tamor valley and one or two level terraces towards the mouth of the tributary valleys reveal periods of tectonic quiescense and a high degree of sediment deposition whereas the steep mountain valley slopes, particularly the vertical topographic breaks between the alluvial terraces (Tars) are the product of high degrees of active tectonism related to the Himalayan uplift and active riverine erosion. The gentler lower Middle, and upper Middle Mountain slopes reflect stabilisation of the landforms and mostly represent stabillised pre-historic landslide areas. The unstable features like landslides, debris flows, gully erosions and rill erosions are the key erosional features within the Tamor basin. The monsoon rains and their intensity are the main factors influencing erosion in the mountaineous slopes as well as along the riverine areas. Areas of instabilities and landslides are more visible and pronounced along the Main Central Thrust (MCT). Existing landslides are concentrated in the vicinity of the MCT, in the southwestern and northwestern parts of the basin (Figure 7.6).

As indicated in Chapter 4, the general landuse in the project area is dictated by the geomorphic forms of the area. The alluvial tars of the valley, and the lower and Middle Mountain slopes are extenssively used for agriculture and human settlement. The steep valley slopes and High mountain slopes are either under forest cover or are very steep, represented by bare rocks with thin soil development. Natural risks of landslides and erosion have been further aggravated by human interventions such as slope disturbance due to deforestation, land use and cover modifications and construction of linear infrastructure (Figures 7.4 and 7.5). Several rural roads are being constructed across the basin with GoN grants allocated to each VDC. These village roads, which were initially supposed to be labor-based, are now being constructed with bulldozers and excavators without any engineering design or supervision, nor any basic erosion or pollution prevention and control measures. The indiscriminate construction of these rural roads has contributed to land destabilization and has further triggered landslides. The roads, which stretch all over the basin, will contribute to an increased sediment load in the Tamor River watershed.

Himalayan rivers are known for their high sediment loads resulting from a high degree of catchment erosion. The monsoon is a period of high sediment load in the river. The Tamor River is one of the rivers in Nepal with the highest sediment load, with reported concentrations as high as 10,000 ppm in extreme events. Historical data on sediment concentrations are often not representative of the true picture as the sediment samples are collected during daylight and do not represent the peak concentrations which often occur during landslides in the middle of the night.

Riverbed morphological change during the monsoon season is a common feature of the Tamor and its tributaries: sand, gravel and boulder deposition in one place and scouring in other places are common. Debris flows are also seen quite frequently on weak and vulnerable slopes along rivers/streams. Change in the riverbed and flood plain morphology of the Tamor and its tributaries brings corresponding change in wet channel characteristics: the pool sections of the wet channels change into rapids, and rapids convert into pool sections on an annual basis. Consequently, aquatic habitat changes are also dynamic.

Figure 7.6 Land use in the Tamor-Kabeli Watershed 


7.7.3 Resident and Migratory Fish Population

The Tamor River has a total length of 198 km and a drop of nearly 5,850 m from its head to the confluence with the Arun at Tribeni. The Kabeli River joins the Tamor halfway between its head and the Arun confluence. There are fragmented reports on the fish diversity of the Koshi and Tamor Rivers. Shrestha, T.K. (1990) has recorded 108 fish species in the Koshi River. Rajbansi (2002) reports about 54 cold-water fish species in the Koshi River of which about 31 species are also reported in the Tamor River. Shrestha, J. (2009) reports 37 species of fish in the Tamor River.

The Tamor and its tributaries together have a rich diversity, with over 50 cold-water fish species reported. This EIA has found 31 species in the Kabeli River just upstream of the Tamor-Kabeli confluence. The EIA for the Tamor Hydropower Project in 1998 enumerated 19 fish species at the project site located upstream of the Tamor-Kabeli confluence. Recently, an EIA for the Upper Tamor Hydropower project reported only 8 fish species at the project site. The headworks of that project are located in the KCA. Table 7.7 presents the list of fish species reported at various periods in the Tamor River basin from both downstream and upstream areas.

A literature review of fishery studies in other Nepalese river basins (Gandaki, Karnali, Mahakali, etc.) and their respective tributaries (Petr, T., 2002; Shrestha, J., 1978, 1994, 1995, 1999, 2002; Shrestha, T.K., 1990, 1995, 1996, 1998, 2002; Rajbansi, J.K, 1982, 1996, 2002, etc.), reveals that the fish species reported for the Tamor River are almost identical to those in other basins. Therefore, the fish species present in the Tamor-Kabeli watershed seem to have a wide distribution range in Nepal.

The decline in fish diversity from downstream to upstream in the Tamor River is quite characteristic of the Himalayan rivers. For this reason the Himalayan rivers are classified into three distinct zones (Shrestha, J., 2002; Petr, T., 2002) based on habitat types. These zones are: (i) Snow trout zone (1,875 – 3,125 m) characterized by fast flowing cold snow-fed water dominated by Schizothorax plagiostomus and other Schizothorax species; (ii) Stone carp zone (1,250 – 1,875 m) characterized by fast flowing waters and dominated by Stone carp (Psilorhynchus pseudecheneis), stone roller (Garragotyla), loach (Noemacheilus spp) and sucker catfish (Glyptothorax spp); and (iii) Hill barbel zone (625 – 1,250 m) characterized by fairly slow water current and dominated by mahseer (Tor tor, T. putitora) and katle (Neolissocheilus hexagonolepis). Normally, the dominant fish species of the Hill barbel zone are not reported in the Snow trout zone, whereas the Stone carp zone is overlapped by species from both the Snow trout and Hill barbel zones. The dominant fish species of the Snow trout and Hill barbell zones migrate upstream and downstream with the changes in discharge volume and temperature.

The species composition and quantity of fish is reported to be rapidly decreasing for the last few years in both the Tamor and Kabeli Rivers. As noted above, this decline is due to unregulated overfishing using poison and electric shock. It is also highly likely that this decline may be partially due to the barrier effect that the large Koshi barrage downstream has had over the past decades on the survival of long-distance migratory fish populations.

Table 7.7 Fish Composition of the Tamor-Kabeli river system

[Please note that a + indicates that the fish species has been reported in the river noted at the heading of each column. The number in parenthesis included next to the name of each river in the heading of the column indicates the study and location referenced as follows: (1) Rajbansi, J.K., 2002; (2) Rajbansi, J,K., 2002; (3) Shrestha, J., 2009; (4) KAHEP project EIA; (5) Tamor/Mewa Hydropower Project site, upstream KAHEP on Tamor River; (6) Upper Tamor Hydroelectric Project site, upstream Tamor/Mewa Hydropower Project site on Tamor River

		Kosi (1)	Tamor (2)	Kabeli (3)	Kabeli (4)	Tamor (5)	Tamor (6)
1	Acanthophthalmus pangia (Hamilton-Buchanan)^20	+	+
2	Amblyceps mangois (Hamilton-Buchanan)	+
3	Anguilla bengalensis			+	+
4	B. barna (Hamilton-Buchanan)	+	+	+
5	B. guttatus (Day)	+
6	B. lohachata (Chaudhuri)	+	+	+	+
7	B. shacra (Hamilton- Buchanan)	+		+	+
8	B. tileo (Hamilton-Buchanan)	+
9	B. vagra vagra (Hamilton-Buchanan)	+	+	+	+	+
10	Bagarius bagarius (Hamilton-Buchanan)	+	+	+	+
11	Balitora brucei (Gray)	+	+
12	Barilius barila (Hamilton-Buchanan)	+	+	+	+	+
13	Barilius bendelisis (Hamilton-Buchanan)	+	+	+	+	+
14	Botiaal morhae (Gray)	+		+	+		+
15	Botia Dario			+
16	Botia histrionic Blyth			+
17	Brachydaniorerio (Hamilton-Buchanan)^8
18	Chagunius chagunio (Hamilton-Buchanan) ^1	+	+			+
19	Chela (Chela) laubuca (Hamilton-Buchanan)^9	+	+
20	Clupiso magarua (Hamilton-Buchanan)	+			+
21	Crossocheilus latius latius (Hamilton-Buchanan)	+		+	+
22	D. devario (Hamilton-Buchanan)	+
23	D.dangila (Hamilton-Buchanan)	+
24	Danio acquipinnatus (McClelland)	+	+
25	Esomus danricus (Hamilton-Buchanan)	+
26	G. annandalei Hora	+	+	+	+	+
27	G. gotylagotyla (Gray)	+	+	+	+	+
28	G. indicus Talwar^22	+	+
29	G. lamta (Hamilton-Buchanan)	+	+
30	G. Nasuta (McClelland)			+
31	G. rupecola (McClelland)	+
32	G. telchitatelchita (Hora)	+	+	+	+
33	Gagatacenia (Hamilton-Buchanan)	+	+
34	Glyptosterrum blythi				+
35	Glyptothorax cavia (Hamilton-Buchanan)	+	+		+	+	+
36	Glyptothorax indicus (Talwar and Jhingran)			+
37	Glyptothorax pectinopterus		+		+	+
38	Heteropneustes fossilis				+
39	L. dero (Hamilton-Buchanan)^2	+	+	+	+	+
40	L. dyocheilus (McClelland)^3	+
41	L.gonius (Hamilton-Buchanan)	+
42	Labeoangra (Hamilton-Buchanan)	+	+	+	+	+
43	Lepidocephalus guntea (Hamilton-Buchanan)^21	+	+
44	Mastacembalus armatus			+	+
45	Myersglanis blythi (Day)			+
46	Naziritor chilynoides (McClelland)	+		+		+
47	Nemacheilus elongates			+
48	Nemacheilus rupicola*					+
49	Neolissocheilus hexagonolepis (McClelland)^4	+	+	+	+	+
50	Noemacheilus beavani				+	+
51	Noemacheilus botia				+
52	Noemacheilus elongates						+
53	P. homaloptera (Hora& Mukherjee)	+
54	P. sucatio (Hamilton-Buchanan)	+
55	Pseudecheneis crassicaudea			+
56	Pseudecheneis sulcatus (McClelland)	+	+		+		+
57	Pseudeutropius atherinoides (Bloch)	+
58	Psilorhynchoides pseudecheneis (Menon&Dutta)	+	+	+	+	+	+
59	Puntius conchonius (Hamilton-Buchanan)	+	+		+	+
60	Puntius Sarana			+
61	Puntius ticto			+	+
62	S. bacaila (Hamilton-Buchanan)	+
63	S. curvoforns (Heckel)
64	S. esocinus (Heckel)	+	+
65	S. labiatus (McClelland)	+
66	S. niger (Heckel)	+
67	S. progastus (McClelland)^15	+	+		+		+
	Schistura multifasciatus			+
68	Schisturaru peculainglisi			+
69	Salmostoma acinaces (Hamilton-Buchanan)	+
70	Schistura scaturigina (McClelland)
71	Schizothora ichthyscurvifrons			+
72	Schizothora ichthyslabiatus			+
73	Schizothora ichthysprogastus			+
74	Schizothorax plagiostomus						+
75	Schizothora xrichardsonii (Gray)	+	+	+	+	+	+
76	Schizothorax siuatus			+
77	Securicula gora (Hamilton-Buchanan)	+
78	Semiplotus semiplotus (McClelland)	+
79	T. mosal (Hamilton-Buchanan)	+
80	T. putitora (Hamilton-Buchanan)	+	+	+	+	+
81	Tor tor (Hamilton-Buchanan) ^5	+	+	+	+	+
	Total Species reported	54	31	37	31	19	8

Fish Species of Conservation Significance:

The IUCN Red list of 2012 has listed five species within the Tamor-Kabeli watershed. The list includes three reported long distance migrants, namely Bagarius yarrelli, Tor putitora and Tor tor. Among the mid-distant migrants, Schizothorax richardsoni and Neolissochilus hexagonolepis, observed during the sampling period of this EIA, are also listed in the IUCN red list. IUCN Red List species that are listed as Critically Endangered are the species of greatest concern whereas the concern decreases for species listed as Endangered and Vulnerable. Of the listed species in the Tamor-Kabeli watershed, the Tor putitora is an Endangered species and Schizothorax richardsoni is a Vulnerable one while others are near threatened species. There are no Critically Endangered species reported in the Tamor-Kabeli watershed.

The species composition and quantity of fish have been reported to be in a rapidly decreasing mode for the last few years in both the Tamor and Kabeli Rivers. However, as noted in Chapter 4, the IUCN Red List is derived from the overall condition of the global population of individual species. The individual species might be in abundance in a particular region but it can be included in the Red List if its global population is decreasing. A similar approach applies to the Red List for the Tamor-Kabeli watershed. For example, Asala, which is the most common species in almost all river systems in Nepal, is included in the IUCN Red List as a vulnerable specie. Similarly, the other four species that are included in the IUCN Red List are reportedly still very common in Nepal.