The Naini Lake
Nainital Lake, a natural freshwater body, situated amidst the township of Nainital in Uttarakhand State of India, tectonic in origin, is kidney shaped or crescent shaped and has an outfall at the southeastern end.
Nainital is most popular hill station of Kumaon district. It is famous for its Naini Lake located at the centre of the town and several other lakes of nearby areas.
Nainital Lake, in the Nainital district called the Lake District of India, is one of the four Lakes of Kumaon hills; the other three lakes are the Sattal Lake, the Bhimtal Lake and the Naukuchiyatal Lake
Historical records confirm that in 1839, Mr. P. Barron, who is supposed to be the first one who visited Nainital, from Rosa, an English business man in sugar trade, on a expedition accidentally coming across the lake at Nainital was so captivated that he decided to build a European Colony on shores of the lake. The news magazine, the Englishman Calcutta, reported in 1841 discovery of this lake near Almora.It is believed that two Indian sages visited there, wandering, it is a belief of people that they blessed the lake with divine power, one can acquire divinement by taking bathe in it, and the same as in the Mansarovar lake.
Topography and Hydrology
The lake is bounded by the high and steep Naina peak on the North West side, by the Tiffin Top to the south west side and snow view peaks on the north. Coniferous forest trees cover these hill ranges. The annual rainfall in the basin area of the lake is reported to be 1294.5 mm (43.15 inches). Tropical monsoon climate with maximum temperature 24.6 °C and minimum of 0.5 °C are recorded. The water is reported to be alkaline in nature (ph value of 8.4–9.3).
The lake receives flows from the surrounding catchment basin which comprises the hill slopes and springs. The hydrologic studies related to water balance and sedimentation was done using radioisotopes for estimating/measuring the various components of the inflow and outflow into the lake. Studies indicated that the subsurface inflow and outflow were significant – ranging from 43 to 63% and 41 to 54%, respectively, of the total inflow and outflow, except in years of exceptionally heavy rainfall. The components of outflows were the surface outflow, the subsurface outflow through the springs on the downstream side and draft through wells for meeting the water supply of Nainital town and evaporation loss from the lake surface. The mean water retention time for the lake was computed as 1.16 years for the mean annual rainfall.
The Krol group of rocks, comprising slates, marls, sandstones, limestones and dolomites with a few small dykes intrusives, is the dominant geological formation of the lake’s surroundings. The lake is deduced to have been formed tectonically. Balia Nala, which is the main stream feeding the lake is along a fault line and the subsequent streams align parallel to major joints and faults. 26 major drains feed the lake including the 3 perennial drains. The lake catchment has highly folded and faulted rocks due to poly phase deformation. Landslides are a frequent occurrence in the hill slopes surrounding the lake, which are steep. The slopes are highly vulnerable to landslides and mass movement due to various geological and human factors. Several landslides have occurred in the past (pictured) around the lake. Many settlements around the lake are located in landslide areas.
A scientific study indicates that the open drains feeding the lake introduce toxic substances from the catchment of the lake, particularly heavy metals which get adsorbed onto the suspended sediments, which in turn settle down in the bottom of the lake. A study of the risk assessment code has revealed that 4–13% of manganese, 4–8% of copper, 17–24% of nickel, 3–5% of chromium, 13–26% of lead, 14–23% of cadmium and 2–3% of zinc exist in exchangeable fraction which puts the lake under the low to medium risk category and infers that it could enter into food chain and also cause deleterious effects to aquatic life. This study provides the basic database to formulate guidelines for the dredging operations and/or restoration programmes in the lake.
The water quality studies carried out by the National Institute of Hydrology during 1999–2001 on physico-chemical parameters (pH, temperature profile, Secchi’s transparency, dissolved oxygen, BOD, COD and nutrients), biological profile (density of population, biomass and species diversity of phyto, zooplankton and macrobenthos) and bacteriological characteristics have led to the conclusion that long-term limnological changes have occurred in the lake. Excess of nutrients inflow have contributed to the eutrophic conditions and the internal recycling of nutrients from sediments during water circulation has resulted in luxurious growth of phytoplankton. The lake is thus anoxic and has reduced hypolimnion, winter circulation, large phytoplankton and relatively lower animal population.
Threats to the lake
The problems facing the lake which were also listed in the plea in a Public Interest Litigation (PIL) before the Supreme Court of India in 1995 seeking court directive for redress measures could be summarised as below:
- The lake is eutrophic to high nutrient accumulation and growth of phytoplankton. Algal blooms had caused loss of transparency. In spite of installing sewer lines to prevent sewage entering the lake still some effluents from drains, leakage and open defecation add to the eutrophication.
- High Siltation resulting in reduction of lake depth (the depth of lake is reported to have reduced from its original depth of 27.97 m to only 19.6m.
- Clogging of water channels (drains) in the surrounding hills because of encroachment, leading to poor drainage.
- Landslides from the unstable hill slopes draining into the lake
- Inadequate sanitation facilities for the poor section of society, commuters and tourists.