LAKE PHEWA

Fish culture in the coastal area


Photo: B.D.Swar  
 

A. LOCATION

• Gandaki Zone, Kaski District, Pokhara, Nepal.
• 28 10 N, 82 05 E; 742 m above sea level.

B. DESCRIPTION

Lake Phewa is one of the largest lakes of Nepal. It is situated in Pokhara Valley in the western part of the country. The main inflows into this lake are two perennial spring - fed streams, Harpan Khola (Khola=stream) and Seti Khola. In addition, several temporary streams drain into the lake belongs to a warm monomictic type with thermal stratification. The lake water has very low electrical conductivity.

Lake Phewa is very young in geological terms as tree trunks are still standing in water down to 6 m depth. There are two versions about the formation of this lake. According to Hagen(1969), there was a "Paleo-Pokhara Lake" filling whole Pokhara basin and the existing lakes are the remails of the former huge lake. But Gurung (1970) and several other workers agree with the view that this lake was formed by damming of tributaries by sediments of Seti River.

Lake Phewa is one of the main sources of recreation, natural beauty, drinking water, hydroelecricity, fisheries and irrigation in Pokhara Valley(1,2,3).

C. PHYSICAL DIMENSIONS

 

Surface area [km2]	5.0
Volume [km3]	39
Maximum depth [m]	21
Mean depth [m]	8.6
Normal range of annual water level fluctuation (regulated) [m]	1
Length of shoreline [km]	18
Catchment area [km2]	110

 

 

D. PHYSIOGRAPHIC FEATURES

D1 GEOGRAPHICAL (6,7,8)

• Bathymetric map: Fig. ASI-04-01(4).
• Main islands (name and area) : Baraki Temple (5~10 4 m2).
• Outflowing rivers and channels (number and name): 1 (Patale Chhango).

Fig. ASI-04-01
Bathymetric map (4).



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D2 CLIMATIC

• Climatic data at Pokhara, 1977-1978

 

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann.
Mean temp. [Ž]	12.6	15.7	20.5	20.8	21.6	23.9	26.1	25.3	24.7	20.6	18.4	13.8	20.3
Precipitation [mm]	23	11	65	278	321	460	718	1,118	332	332	101	54	1,556

 

• Water temperature [Ž] (2)

Station1, 1977-1978

Depth[m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Surface(0)	16	17	20	23	-	27	28	27	27	22	20	18
4	16	16	19	22	-	26	25	25	25	22	20	18
8	16	16	17	18	-	20	22	23	23	22	20	18
10	16	-	17	17	-	19	20	22	22	22	20	18
12	16	16	17	17	-	19	20	21	22	22	20	18
14	16	16	16	17	-	19	19	20	21	22	20	18
16	16	16	16	17	-	19	19	20	21	22	20	18
18	16	16	16	17	-	18	19	20	21	22	20	18

 

• Freezing period: None.
• Mixing type: Monomictic.
• Notes on water mixing and thermocline formation : A stable temperature stratification exsits from the end of February until October. The pattern is of a classical mononictic type with one turnover in winter.

E. LAKE WATER QUALITY (6,7,8,9,10,11)

E1 TRANSPARENCY [m] Station 1, 1977-1978

Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
4	3	1.7	2	1.6	1.7	1.9	1.3	2.6	2	2.4	1.8

E2 pH (2)

Station 1, Sep. 10, 1984

Depth[m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
0	-	-	-	-	-	-	-	-	8.3	-	-	-
	-	-	-	-	-	-	-	-	8.3	-	-	-
2.5	-	-	-	-	-	-	-	-	8.0	-	-	-
5	-	-	-	-	-	-	-	-	6.9	-	-	-
10	-	-	-	-	-	-	-	-	6.4	-	-	-
15	-	-	-	-	-	-	-	-	6.9	-	-	-
20	-	-	-	-	-	-	-	-	6.9	-	-	-

 

E4 DO [mg l-1] ,Station 1, 1977-1978

 

Depth[m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
0	9	10	10	9	-	9	8	8	8	8	8	8
4	9	9	9	9	-	6	6	6	7	8	8	8
8	9	9	5	0	-	0	1	2	0	5	2	8
10	9	9	3	0	-	0	0	0	0	4	1	8
12	9	9	2	0	-	0	0	0	0	4	1	8
14	9	9	2	0	-	0	0	0	0	1	0	8
16	9	9	2	0	-	0	0	0	0	0	0	8
18	9	9	2	0	-	0	0	0	0	0	0	8

 

E6 CHLOROPHYLL CONCENTRATION [ƒÊg l-1] ,Sep. 10, 1984

 

Depth[m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
0	-	-	-	-	-	-	-	-	4.8	-	-	-
1	-	-	-	-	-	-	-	-	5.6	-	-	-
2.5	-	-	-	-	-	-	-	-	6.5	-	-	-
5	-	-	-	-	-	-	-	-	15.3	-	-	-
10	-	-	-	-	-	-	-	-	1.3	-	-	-
15	-	-	-	-	-	-	-	-	1.1	-	-	-
20	-	-	-	-	-	-	-	-	1.1	-	-	-

 

E7 NITROGEN CONCENTRATION (2)

• Total-N* [mg l-1], Station 1, Sep.10, 1984

 

Depth[m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
0	-	-	-	-	-	-	-	-	0.117	-	-	-
2.5	-	-	-	-	-	-	-	-	0.197	-	-	-
5	-	-	-	-	-	-	-	-	0.163	-	-	-
10	-	-	-	-	-	-	-	-	0.326	-	-	-
15	-	-	-	-	-	-	-	-	1.010	-	-	-
20	-	-	-	-	-	-	-	-	1.202	-	-	-

* Total-N is estimated from PON and DTN concentrations.

E8 PHOSPHORUS CONCENTRATION

• Total-P [mg l-1], Station 1, Sep.10, 1984

Depth[m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
0	-	-	-	-	-	-	-	-	0.011	-	-	-
2.5	-	-	-	-	-	-	-	-	0.012	-	-	-
5	-	-	-	-	-	-	-	-	0.011	-	-	-
10	-	-	-	-	-	-	-	-	0.011	-	-	-
15	-	-	-	-	-	-	-	-	0.018	-	-	-
20	-	-	-	-	-	-	-	-	0.026	-	-	-

 

F. BIOLOGICAL FEATURES

F1 FLORA

• Phytoplankton: Merismopedia elegans, Microcystis spp., Synura petersenii, Dinobryon divergens, Mallomonas spp., Navicula rhyncocepala, Navicula spp., Cyclotella spp., Tabellaria fenestrata, Diatomella spp., Stephanodiscus carconensis, Nitchia acicularis, Melosira granulata, M. italica, M. spp., Synedra acus, Surirella robusta, Rhoicosphenia curvata, Botryococcus braunii, Centritractus belonophorus, Ceratium hirundinella, Gymnodinium spp., Peridinium spp., Crytomonas compressa, C. spp., Gonyostumum semsu, G.spp., Staurastrum pseudopelagicum, S. dimazum, S. dorsidentiferum, S. curvatum, S.spp., Srthrodesmus triangularis, A. ralfsii, Arthrodesmus spp., Euastropsis richteri, Cosmarium contractum, C. reniforme, Cosmarium spp., Spondirosium spp., Closterium spp., Oocystis lacustris, O. spp., Nephrocytium spp., Glaeotaenium loitelsbergerianum, Tetraedron hastatum, Crucigenia tetrapedia, Galenkinia radiata, Carteria cordiformis, Chlamydomonas moewusii, Dictyospherium ehrenbergianum, D. pulchellum, Gonotozygon pilosm(7,9).

F2 FAUNA

• Zooplankton: Rotifera (Collotheca sp., Conochilus unicornis, Hexarthra mira, Keratella cochlearis, K. tropica, Brachionus patulus, Tricocera cylindrica, T. similis) ; Cladocera (Diaphanosoma excisum, Daphnia longispina, D. lumholtzi, Ceriodaphnia reticulata, C. cormuta, Simocephalus vetulus elisabethae, Bosmina longirostris, Eubosmina coregoni, Moina micrura ) ; Copepoda (Neodiaptomus strigilipes, Phyllodiaptomus blanci, Mesocylops leuckarti, Thermocyclops crassus, Tropocyclops confinis, Chaoborus sp.) (12,13,14,15,16,17).

Fig. ASI-04-02. Seasonal abundance of Crustacean zooplankton in Lake Phewa, Jan.-Dec., 1977. Numbers represent the animals/m2 and histograms represent the percentage of different groups(15).

Months	Diaphanosoma excisum	Daphinia longispina	Daphnia lumholtzi	Ceriodaphnia cornuta	Bosmina longirostris	Moina micrura	Calanoida	Cyclopodia	Nauplii	Chaoborus spp.
Jan	116,900	1,200	5,600	5,800	200	-	77,800	6,600	6,000	1,200
Feb	54,200	1,100	84,700	4,100	300	-	56,700	2,700	6,000	2,400
Mar	15,400	2,700	157,200	33,900	6,200		48,800	8,400	25,200	-
Apr	4,500	-	2,200	2,100	-	-	22,100	13,600	7,500	200
May	41,100	-	-	1,200	500		12,100	9,200	5,100	0
Jun	4,900	-	-	3,500	-	12,200	8,400	1,500	3,900	1,200
Jul	2,400	-	400	1,500	-	7,200	6,300	3,900	3,900	900
Aug	5,100	-	800	-	400	3,600	5,500	3,900	2,100	1,600
Sep	51,300	-	2,300	35,400	85,500	10,600	23,100	608,600	130,300	1,700
Oct	1,400	1,100	58,800	1,200	400	-	14,000	21,000	4,100	2,900
Nov	3,800	300	800	15,000	700	-	3,000	9,000	6,600	2,100
Dec	26,500	200	19,100	1,000	-	-	25,600	4,500	2,700	1,000

 

• Fish : Barilius barna, B. bendelensis, Cirrhinus rewa*, Labeo gonius*, L. rohita*, Puntius sarana, P. sophora*, Tor tor*, T. putitora*, Acrossochielus hexagonolepsis*, Anguilla bengalensis, Xenentodon cancilla, Channa gachua, Mastacemgbelus armatus, Aristichthys nobilis*, Hypophthalmichthys molitrix.*, Ctemophargodon idellus*, Cyprinus carpio* (economically important) (18,19).

F3 PRIMARY PRODUCTION RATE [mg O2 l-1 hr-1] ,1977-1978 (6)

 

	Annual total
Net production	0.35
Dark respiration	1.85
Gross production	2.2

* Estimated by a modified light/dark oxygen method.

F5 FISHERY PRODUCTS

• Annual fish catch in 1985 : 40 [metric tons].

G. SOCIO-ECONOMIC CONDITIONS (Q)

G1 LAND USE IN THE CATCHMENT AREA

 

	Area [km2]	[%]
Natural landscape
Woody vegetation	30	27
Herbaceous vegetation	10	9
Swamp	2	2
Others	8	8
Agricultural land
Crop field	20	18
Pasture land	20	18
Residential area	20	18
Total	110	100

 

• Main types of woody vegetation : Subtropical deciduous broad leaf forest.
• Main types of crops : Rice, maize, wheat, fruit trees.
• Levels of fertilizer application on crap fields : Light.

G2 INDUSTRIES IN THE CATCHMENT AREA AND THE LAKE (1984)

 

	Gross product per year [US $]
Fisheries	75,000

 

G3 POPULATION IN THE CATCHMENT AREA

 

		Population	Population density [km-2]	Main cities
Urban	ca.	10,000	-	Pokhara
Rural	ca.	5,000	-
Total	ca.	15,000	136

 

H. LAKE UTILIZATION (Q)

H1 LAKE UTILIZATION

Sightseeing and tourism (number of visitors in 1984 : 50,000), recreation (swimming, sport fishing, yachting), fisheries and source of water.

H2 THE LAKE AS WATER RESOUCE (1984)

 

	Use rate [m3 sec-1]
Domestic water	1.2 x 10-4
Irrigation	10
Power plant	10

 

I. DETERIORATION OF LAKE ENVIRONMENTS AND HAZARDS (Q)

I1 ENHANCED SILTATION

• Extent of damage: Serious.
• Supplementary notes: The lake is receiving heavy silt loads every year during the rainy season due to the derorestration on the northern belt of the watershed area.

I3 EUTROPHICATION

• Nuisance caused by eutrophication: None.

I4 ACIDIFICATION

• Extend of damage: None.

M. LEGISLATIVE AND INSTITUTIONAL MEASURES FOR UPGRANDING LAKE ENVIRONMENTS (Q)

M3 RESEARCH INSTITUTE ENGAGED IN THE LAKE ENVIRONMENT STUDIES

1. Fisheries Development Center, Baidam, Phewa Tal, Pokhara, Nepal

N. SOURCES OF DATA

(Q) Questionnaire filled by Mr.Deep B. Swar, Fisheries Development Center, Pokhara, Nepal, based on the data from the following sources.

(1)    Hagen, T. (1969) Report on the geological survey of Nepal. Vol.1. Preliminary reconnaissance. Denkshr. d. Schweiz. Naturf. Ges., 86: 1-185
(2)    Gurung, H., (1970) Geomorphology of Pokhara Valley. Himalayan Review, 2/3 : 37-49.
(3)    Yamanaka, H., Yoshida, M. & Arita, K. (1982) Terrace landform and quaternary deposit around Pokhara Valley, central Nepal. Journal of Nepal Geological Society, 2 : 113-142.
(4)    Ferro, W. & Swar, D. B. (1978) Bathymetric maps from three lakes of the Pokhara Valley (Nepal). J.Inst Sc. Tribhuvan University, Kathmandu, Nepal, 1: 177-188.
(5)    Swar, D.B. (1980) Present status of limnological studies and research in Nepal. "Proceedings of the First Workshop on the Promotion of Limnology in the Developing Countries" (ed. Mori, S. & Ikushima , I.), pp.43-47. XXI SIL Congress, Kyoto.
(6)    Ferro,W. (1981/1982) Limnology of the Pokhara Valley lakes (Himalayan Region, Nepal) and its implication for fishery and fish culture. Journal of Nepal Research Center, Kathmandu, Nepal, 5/6 : 27-52.
(7)    Hickel, B. (1973) Limnological investitations in lakes of the Pokhara Valley, Nepal. Int. Revue ges. Hydrobiol., 58 : 659-672.
(8)    Swar, D.B. & Fernando, C.H. (1980) Some studies on the ecology of limnetic crustacean zooplankton in Lakes Begnas and Rupa, Pokhara Valley, Nepal. Hydrobiologia, 70 : 235-245.
(9)    Nakanishi, M. (1986)    Limnological study in Phewa, Begnas and Rupa Lakes. "Studies on Distribution, Adaptation and Evolution of Microorganisma in Nepal Himalaya (Second Report)"(ed. Ishida, Y.), pp.1-13. Kyoto Univ., Kyoto.
(10)    Nakanishi, M., Terashima, A., Watanabe, M. & Misra, P. (1984) Preliminary report on limnological survey in lakes of Pokhara Valley (Nepal) in November-Dexember, 1982. "Studies on Distribution, Adaptation and Evolution of Microorganisms in Nepal Himalaya (Preliminary Report)" (ed. Kadota, H.), pp.31-41. Kyoto Univ., Kyoto.
(11)    Kato, K. & Hayashi, H. (1982) Limnological presurvey of Lake Phewa, Nepal J. Fac. Sc. Sinshu Univ., 15 : 27-29.
(12)    Swar, D. B. & Fernando, C.H. (1979a) Seasonality and fecundity of Daphnia lunholtzi Stars in Lake Phewa Nepal. Hydrobiologia, 64 : 261-268.
(13)    - & - (1979b) Cladocera from Pokhara Valley, Nepal with notes on Hydrobiologia, 66 : 113-128.
(14)    Swar, D. B. (1979) Some studies on freshwater crustacean zooplankton (natural fish food) from Nepal. M. Sc. thesis, University of Waterloo, Ontario, Canada, 152 pp.
(15)    - (1981) Seasonal abundance of limnetic crustacean zooplankton in Lake Phewa, Pokhara Valley, Nepal. Verh. Int. Ver. Limnol., 21 : 535-538.
(16)    Dumont, H. J. & van de Velde, I. (1977) Report on the collection of Cladocera and Copepoda from Nepal. Hydrobiologia, 53:1:55-65.
(17)    Deans, G. & Dumont, H. J (1974)    Rotifers from Nepal, with description of a new species of Scaridium and a discussion of Nepalese representative of the genus Hexarthra. Biol. Jb. Dodonaea, 42:61-81.
(18)    Ferro, W. (1980)    Data on the fishery in Pokhara Valley (Nepal) and their implications for the fishery management. J. Inst. Sc. Tribhuvan University, Kathmandu, Nepal, 3:221-236.
(19)    - & Badagami, P.R.(1980)    On the biology of the commercially important species of fish of the Pokhara Valley (Nepal). J. Inst. Sc., 3:237-250.