A Directory of Wetlands in New Zealand: Canterbury Conservancy
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A Directory of Wetlands in New Zealand CANTERBURY CONSERVANCY Sumner Lakes Complex (56) Location: 42o42'S, 172o13'E. In the Hurunui River catchment in inland North Canterbury, east of the main divide, South Island. Hawarden township (50 km southeast) is the nearest settlement. Lake Sumner, the largest lake, is 137 km by road and track northwest of Christchurch. Formed public roads end at Lake Taylor, 11 km south of Lake Sumner. The other lakes are accessible by either rough vehicle tracks or walking tracks. Within Sumner Ecological District Area: c.1,870 ha. Altitude: 523-676 m. Overview: The Sumner Lakes Complex is made up of Lake Sumner, a deep, medium-sized oligotrophic lake; five small deep lakes, namely, Loch Katrine and lakes Marion, Taylor, Sheppard and Mason; and two shallow wetlands, Lake Mary and Raupo Pond. The smaller lakes are all within 10 km of Lake Sumner. During the Pleistocene, various lobes of a glacier carved the Hurunui Valley and several adjacent valleys and basins. The lakes occupy moraine- dammed troughs within the valleys. The complex is very similar to the Coleridge Lakes Complex in terms of physical character, origin and climate. The Sumner Lakes, like the Coleridge Lakes, are used by Great Crested Grebes Podiceps cristatus australis, and also support large populations of Paradise Shelduck Tadorna variegata and the introduced Canada Goose Branta canadensis. Lake Sumner is the best example of a forested lake catchment in the eastern South Island. Lake Sumner Forest Park extends over part of the Lake Sumner and Lake Mason catchments. Lake Marion is partially protected as a Faunal Reserve. Most of the lakes are popular recreation sites, particularly for game-bird shooting, fishing, boating, camping and walking. There are no major threats to the lakes at present. In the 1970s, however, there were proposals for hydro-electric power development in the Hurunui River. Physical features: Lake Sumner (1,080 ha, 134 m deep) is a cold oligotrophic lake in inland North Canterbury, formed approximately 18,000 years ago (Kenny & Hayward, 1993). It occupies a deep trough, 9.7 km long by 2.4 km wide, within the glacially-carved Hurunui River Valley. The upper Hurunui River enters the lake via a shingle delta and drains through a narrow, natural channel at the south eastern end of the lake. The lake buffers stream flows in the lower river. Lake levels vary within a natural range of 3.5 m. The stony shoreline is subject to heavy wave action, as strong northwesterly winds funnel down the lake. Waters do not show temperature stratification. Lake Sumner is usually clear, with a low algal content (Livingston et al., 1986b). Floods in the upper catchment cause minor discoloration in the lake. Lake Marion (15 ha, depth not known) is an isolated and unmodified lake north of Lake Sumner. It is drained by Marion Stream, which feeds into Lake Sumner. Loch Katrine (75 ha, 28 m deep) is one of the five smaller glacial lakes in the vicinity of Lake Sumner but outside the Hurunui valley. Loch Katrine lies within a steep-sided valley, dammed by moraine and alluvial fans. Minor streams feed into the lake. Drainage into Lake Sumner is via a narrow channel and low-lying swampland at the loch's northwestern end. Most of the lake is surrounded by steep shingle beaches. A small shingle spit creates an area of sheltered water in this usually windswept lake. Lake Taylor (185 ha, 40.5 m deep) and Lake Sheppard (115 ha, 21 m deep) are south east of Loch Katrine, in the same glacial valley. A low hill separates lakes Taylor and Sheppard. They are moraine-dammed, and drain via Raupo Pond and Sisters Stream into the Hurunui River - 216 - A Directory of Wetlands in New Zealand below Lake Sumner. They are of similar physical character to Loch Katrine. Lake Taylor is the most accessible of all the Sumner Lakes. Lake Mason (53 ha) is an isolated lake southwest of Loch Katrine, within the Hurunui River South Branch catchment. Two shingle spits have built out from opposite shores, dividing the lake into two basins. The north basin (35 ha) is 38.5 m deep, whereas the south basin (18 ha) is only 1.9 m deep. Raupo Pond (13 ha) and Lake Mary (18 ha) occupy shallow depressions on moraine and outwash gravels beside Lake Sheppard. Ecological features: The lakes are surrounded by steep hill sides covered in either mountain beech forest (Nothofagus solandri var. cliffortioides) or mosaics of fire-induced shrub, forest and tussock grassland. Forest is most extensive north of Lake Sumner. Around Lake Taylor, Lake Sheppard and Loch Katrine, outwash surfaces, moraines and alluvial fans have been farmed for over 100 years. Submerged aquatic vegetation in the Sumner Lakes Complex was surveyed in 1987, and described by de Winton et al. (1987). The report includes recommendations for management of aquatic plants. The aquatic vegetation is closely comparable with other inland South Island glacial lakes. Common species of shallow water are Glossostigma submersum and Elatine gratioloides. Isoetes alpinus dominates littoral margins. Charophyte diversity is high, with four species of Chara and four of Nitella. Two species, Chara braunii and Nitella stuartii, are uncommon species. Bryophytes are found down to 34 m depth. The introduced weed Elodea canadensis is widespread, except in Lake Marion, which has only native species. More undesirable weeds such as Lagarosiphon major are not yet present. There has been relatively little research into water quality of the Hurunui Lakes (Bowden, 1977). Existing data do not concur in terms of trophic status of all the lakes. Seasonal variations and assessment criteria may account for some of the variation. The trophic status of each lake is discussed below. Results of chemical analyses are presented in Bowden (1977). Lake Sumner possesses a diversity of habitats, i.e. braided river delta, lake margin swamplands, a large area of open water and extensive forest adjacent to the lake shore. The lake is classed as highly oligotrophic, as is typical of deep glacial lakes in New Zealand. Lake Marion is of particular biological significance because it is free from introduced fish and completely enclosed by forest. The lake has been described as mildly mesotrophic and, alternatively, "dystrophic" and in a state very similar to lakes of Westland where brown humic material has leached from surrounding forest. (Dystrophic usually describes water that has deteriorated to a state of low productivity. However, some lakes rich in humic material may be highly productive (Jolly & Brown, 1975, cited in Bowden, 1977). Loch Katrine is bounded by beech forest on one side, and tussock grassland on the other. The loch is variously classed as oligotrophic or mesotrophic. Lake Taylor is surrounded by partly developed tussock pasture. The lake margin is heavily vegetated with New Zealand Flax Phormium tenax, Matagouri Discaria toumatou and Manuka Leptospermum scoparium (Lewis, 1983). This lake is classed as oligotrophic. The margins of Lake Sheppard are dominated by Raupo Typha orientalis, New Zealand Flax and Carex species. Trophic status assessments vary between oligotrophic and mildly mesotrophic. Lake Mason lies within a catchment dominated by mountain beech forest. The main part of this lake is highly oligotrophic, whereas the shallow area known as Little Lake Mason is mesotrophic. Raupo Pond is a large area of open water, surrounded by raupo swamp with willow trees. Lake Mary is a small area of open water is surrounded by an extensive flax and sedge swamp. Land tenure: Lake beds are Crown land reserved from sale. Lakes and rivers in this area are lined with Crown land Section 58 (Land Act 1948) marginal strips. Other tenures are - 217 - A Directory of Wetlands in New Zealand unalienated Crown land (as at Raupo Pond), Crown Pastoral Lease (Lake Mary) and Crown Conservation area within Lake Sumner Forest Park (Lake Marion). Most land surrounding Lake Sumner and Lake Mason is within Lake Sumner Forest Park managed by the Department of Conservation. Elsewhere, Crown Pastoral Lease tenure predominates. Other tenures include freehold title and legal road. There are camping reserves at Lake Taylor and Lake Sumner, and a Crown-owned Recreation Reserve at the southern end of Loch Katrine. There is no legal public access to Lake Mary or Lake Sheppard. Conservation measures taken: Lake Marion is a "Faunistic Reserve" under the Freshwater Fisheries Regulations, 1951 (New Zealand Forest Service, 1979). This designation is to preserve the biological status of the lake waters by prohibiting introduction of any fish, other animal or plant. Lake Sumner Forest Park adjoins Lake Sumner and Lake Mason, but only Lake Marion is included in the park. All lakes, except Lake Sheppard, were closed game areas up until 1977. The then North Canterbury Acclimatisation Society wanted to encourage breeding of the introduced Canada Goose Branta canadensis. However, protection was removed because of high goose numbers and the damage the geese caused to crops on local farms. Lake Marion was selected as a Project Aqua lake (part of an international biological research and protection programme). It was considered a representative and little-disturbed freshwater lake (Davis, 1984; Luther & Rzoska, 1971). Conservation measures proposed: None. Land use: The lakes are wildlife habitats. Recreation is the only other main use of the wetlands. Lake Sumner Forest Park is managed for its conservation values and for recreational use. Pastoral Lease land is used for extensive grazing of sheep and cattle. Human settlement in the upper Hurunui catchment is limited to a few isolated homesteads and an informal settlement of 40 huts and caravans at Loch Katrine. The Loch Katrine huts and Recreation Reserve are the subject of a recent draft management plan (Department of Conservation, 1993a).