LAKE TAUPO

On the lakeshore at Taupo


Photo: A.Kurata

A. LOCATION

• South Auckland-Bay of Plenty, New Zealand.


• 38:45S, 175:55E; 357 m above sea level.

B. DESCRIPTION

Lake Taupo is located at the centre of the North Island of New Zealand, and is the largest in that country. The drainage basin of the lake is characterized by a mild climate; moderate temperature, light winds, cool summers, relatively warm winters and a fairly even distribution of rainfall throughout the year. The lake is surrounded by gently sloping hills which offer pasture for sheep. About 30 rivers flow into the lake, while the Waikato River is the only outlet. There are two towns, large and small, around the lake. Taupo is the main town which is located at the mouth of the Waikato River. Tall eucalypti, which are characteristic in New Zealand and Australia, are abundant on the lake shore of the town. The lake water is clear and highly transparent, with a maximum transparency of 21 m. The concentration of nitrogen and the nitrogen/phosphorus ratio of the water are remarkably low. This may be mainly attributed to the geology of the catchment area, and is responsible for the oligotrophic level of its productivity. The Koaro and the Toitoi are fish native to the lake. The Koaro, with a flat head and tough but slimy skin, was an important fish resource for the Maori living around the lake, but has become very scarce. On the other hand, artificially stocked rainbow trout is now abundant, and is primarily important for sport-fishing. The common smelt was also introduced to the lake between 1934 and 1940 after the average size of trout declined (2).

C. PHYSICAL DIMENSIONS

Surface area [km2]	616
Volume [km3]	60
Maximum depth [m]	164
Mean depth [m]	91
Water level	Regulated
Length of shoreline [km]	153
Residence time [yr]	10.6
Catchment area [km2]	3,327

D. PHYSIOGRAPHIC FEATURES

D1 GEOGRAPHICAL

• Bathymetric map: Fig. OCE-01-01.


• Names of main islands: None.


• Number of outflowing rivers and channels (name): 1 (Waikato R.).

D2 CLIMATlC

• Climatic data at Taupo, 1949-1970 (1)

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann.
Mean temp. [deg C]	17.1	17.3	15.6	12.5	9.6	7.3	6.3	7.4	9.3	11.5	13.5	15.6	11.9
Precipitation [mm]*													1,200

* Even distribution.

• Snowfall: None.

Fig. OCE-01-01
Bathymetric map (2).

• Water temperature [deg C](1)

Lake centre, 1974-1976
Depth [m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
S*	22	20	18	16	13	12	11	11	13	15	18	20

* Surface.

• Freezing period: None.


• Mixing type: Monomictic.


• Notes on water mixing and thermocline formation
  The thermocline is formed from December to June.

E. LAKE WATER QUALITY

E1 TRANSPARENCY [m](1)

Lake centre, 1974-1976
Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
-	-	15	15	-	-	-	11	11	-	20	20

E2 pH (1)

Lake centre, 1974-1976
Depth [m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
S*	7.4	8.1	-	8.4	7.9	7.3	7.2	7.5	7.0	7.6	7.3	7.5

* Surface.

E3 SS [mg l-1](1)

Lake outlet: 0.5-1.0 (estimated range).

E4 DO [mg l-1](1)

Lake centre, 1974-1976: Saturated at all times above 75 m depth.

E6 CHLOROPHYLL CONCENTRATION [micro l-1](3)

Lake centre, 1975-1976
Depth [m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
0-30	1.0	1.0	1.0	0.8	1.0	1.2	1.7	2.8	2.4	2.0	1.2	1.1

E7 NITROGEN CONCENTRATION (3)

• NO3-N [micro l-1]

Lake centre, 1975-1976
Depth [m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
*1	0.6	2.2	1.0	0.3	0.4	0.3	1.0	1.0	0.4	0.6	0.8	0.4
*2	14	17	18	17	20	21	23	2	3	1	7	9

*1 Epilimnion. *2 Hypolimnion.

• NH4-N [mg l-1]

Lake centre, 1975-1976
Depth [m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
*1	.014	.007	.005	.004	.002	.002	.002	.006	.002	.004	-	.009
*2	.007	.006	.005	.002	.001	.002	.003	.003	.003	.005	-	.006

E8 PHOSPHORUS CONCENTRATION (3)

• Total-P [mg l-1]*

Lake centre, 1975-1976
Depth [m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
-	.006	.004	.005	.001	.008	.007	.009	.010	.012	.006	.005	.002

* Mean for profile.

Fig. OCE-01-02
Trend of T-P at Station A (38:47S, 176:02E), Station B (38:52S, 175:51E) and Station C (38:44S, 175:48E)(vertical bars encompass 99% confidence limits)(3).

F. BIOLOGICAL FEATURES

F1 FLORA

• Submerged macrophytes

Chara corallina, Nitella hyalina, N. flexilis, N. hookeri, Elodea canadensis, Lagarosiphon major, Potamogeton crispus.
• Phytoplankton

Melosira granulata, Asterionella formosa, Chroococcus spp., Ankistrodesmus spp., Cyclotella spp.

F2 FAUNA

• Zooplankton

Crustacea (Boeckella propinqua, Macrocyclops albidus, Ceriodaphnia dubia, Bosmina meridionalis, Daphnia carinata); Rotifera (Polyarthra vulagris, Pompholyx sp., Asplanchna brightwelli).
• Benthos

Paranephrops planifrons, Chironomus zealandicus, Potamopyrgus antipodarum, Lymmaea stagnalis, Cyraulus corinna, Hyridella menziesi.
• Fish

Galaxias brevipinnis, Gobiomorphus cotidianus, Retropinna retropinna, Salmo trutta, S. gairdneri.
• Supplementary notes on the biota: Fig. OCE-01-03.

Fig. OCE-01-03
Depth distribution of the most common invertebrate animals of the bottom sediments (2).

F5 FISHERY PRODUCTS (2)

• Annual fish catch [metric tons]
  1966-1967: 671.

F6 PAST TRENDS OF FISHERY PRODUCTION: Fig. OCE-01-04 and 05.

Fig. OCE-01-04
Average weight of rainbow trout in anglers' bags in Lake Taupo; catchment every five year since 1905. Separate points are shown for years 1911, 1917 and 1924. These years mark maximum peaks and troughs at a critical period of the fishery (2).

Fig. OCE-01-05
Total sales of fishing licenses for Lake Taupo and catchment 1930/31 season to 1980/81 season (2).

G. SOCIO-ECONOMIC CONDITIONS

G1 LAND USE IN THE CATCHMENT AREA (Q1) (1973)

	Area [km2]	[%]
Natural landscape
- Indigenous forest (including alpine and subalpine vegetation)	75.6	28
- Tree plantation (exotic)	36.3	14
- Scrub	69.8	26
- Tussock grassland	33.7	13
Agricultural land
- Pasture land	46.9	18
Residential area	3.2	1
Total	265.5	100

• Main types of woody vegetation
  Mixed evergreen broadleaf/conifer forest (Nothofagus, Podocarpus); pine plantation (Pinus radiata); lowland scrub (Leptospermum, Coriaria).
• Main types of herbaceous vegetation
  Tussock grassland; clover-ryegrass pasture.

G2 INDUSTRIES IN THE CATCHMENT AREA AND THE LAKE (Q1) (1982)

	No. of persons engaged	Main products or major industries
Primary industry
- Agricultural	282	Meat, wool, logs and posts
Secondary industry
- Manufacturing	978
- Mining	9
- Others	572
Tertiary industry	3,627

G3 POPULATION IN THE CATCHMENT AREA (Q1) (1982)

	Population	Population density [km-2]	Major cities (population)
Total	25,500	7.7	Taupo, Turangi

H. LAKE UTILIZATION (Q1)

H1 LAKE UTILIZATION

Source of water, sightseeing and tourism, recreation (swimming, sport-fishing, yachting).

H2 THE LAKE AS WATER RESOURCE (1982)

	Use rate [m3 sec-1]
Domestic	0.10
Power plants*	N.A.

* Waters of Taupo catchment and Waikato River provides a total of 1,371 MW of hydroelectric power.

I. DETERIORATION OF LAKE ENVIRONMENTS AND HAZARDS

I1 ENHANCED SILTATION

• Extent of damage: Not serious.

I2 TOXIC CONTAMINATION

• Present status: None.

I3 EUTROPHICATION

• Nuisance caused by eutrophication: Not any nuisance.


• Nitrogen and phosphorus loadings to the lake [t yr-1](Q1, 1) (1973-1974)

Sources	Agricultural	Natural	Total
T-N	Minor	Major	657
T-P	Minor	Major	116

I4 ACIDIFICATION

• Extent of damage: None.

J. WASTEWATER TREATMENTS

J1 GENERATION OF POLLUTANTS IN THE CATCHMENT AREA

(b) No sources of significant pollution.

J3 SANITARY FACILITIES AND SEWERAGE (Q2, 2)

• Municipal wastewater treatment systems
  No. of secondary treatment systems: 1 (more under construction; activated sludge and oxidation pond).
  No. of other types: Many of the urban communities near the shores of the lake use septic tanks to dispose of wastewater.

K. IMPROVEMENT WORKS IN THE LAKE

K1 RESTORATION (2)

Lake Taupo Catchment Control Scheme, Soil Conservation, Run-off Control and Water Management in the total catchment of 266,000 ha. Implementation period: 1974-1987. Approximate total cost: NZ$ 6,000,000.

L. DEVELOPMENT PLANS (Q2)

Water diversions and power stations are planned in the catchment area. The diagram of the Tongariro Power Development Scheme is shown in Fig. OCE-01-06.

Fig. OCE-01-06 (Q2)
Diagram of the Tongariro Power Development Scheme.

M. LEGISLATIVE AND INSTITUTIONAL MEASURES FOR UPGRADING LAKE ENVIRONMENTS (Q1,Q2)

M1 NATIONAL AND LOCAL LAWS CONCERNED

• Names of the laws (the year of legislation)


1. Soil conservation and Rivers Control Act (1941)
2. Water and Soil Conservation Act (1967)
3. Local Government Act (1974)
4. Town and Country Planning Act (1977)
• Responsible authorities


1. Taupo County Council
2. Waikato Valley Authority
3. Tongariro United Council
• Main items of control


1. Water rights
2. Soil conservation works
3. District schemes
4. Clearance of ground cover by-law and subdivisional controls

M2 INSTITUTIONAL MEASURES

1. Waikato Valley Authority
2. Electricity Division, Ministry of Energy
3. Department of Internal Affairs
4. Federation of Lake Taupo Angling. Shooting and Boating Societies
5. Lake Taupo Advisory Committee
6. New Zealand Forest Service
7. Department of Lands and Survey
8. Tongariro-Taupo Parks and Reserves Board
9. Taupo and Taumarnui County Councils

M3 RESEARCH INSTITUTES ENGAGED IN THE LAKE ENVIRONMENT STUDIES

1. Ministry of Works and Development
2. DSIR-Taupo Research Laboratory
3. Aquatic Weeds Section of Ministry of Agriculture and Fisheries
4. Fisheries Research Division of Ministry of Agriculture and Fisheries
5. Department of Internal Affairs-Wildlife Service

N. SOURCES OF DATA

17. Questionnaire filled by the Department of Scientific and Industrial Research. (Q1)
17. Questionnaire filled by Dr. D. G. Smith, National Water and Soil Conservation Organization. (Q2)
1. Data supplied by Dr. M. Timperley, Ecology Division, Department of Scientific and Industrial Research.
2. Forsyth, D. J. & Howard-Williams, C. (1983) Lake Taupo, Ecology of a New Zealand Lake. New Zealand Department of Scientific and Industrial Research, Information Series No. 158. 163 pp. Science Information Publishing Centre, DSIR, Wellington.
3. White, E., Downes, M., Gibbs, M., Kemp, L., Mackenzie, L. & Payne, G. (1980) Aspects of the physics, chemistry, and phytoplankton biology of Lake Taupo. N. Z. J. Mar. Freshw. Res., 14: 139-148.