Study on Anasagar Lake
— by Pratyush S, August 12 2021 —
Constructed by building a dam across the Luni river in the 12th century, Anasagar is an artificial lake and the largest lake in the city of Ajmer, Rajasthan. Named after the grandfather of Prithivi Raj Chauhan who built it during the period 1135-1150 AD – King Anaji Chauhan, the lake was later added with Daulatbagh gardens and Baradari (pavillions) by Mughal Emperors Jehangir and Shah Jahan, respectively. On a hill near the lake, a circuit house is situated which earlier served as British Residency. The lake has a slightly higher pH than the limit mentioned in the Central Pollution Control Board (CPCB) guidelines, and the water is not fit for human consumption. However, the water quality in Anasagar Lake is better now than it was a few years ago. The Dissolved Oxygen (DO) is within the recommended limits but Biochemical Oxygen Demand (BOD) and Coliform counts are above the acceptable human use limits which makes the water unsuitable for bathing too. The temperature has a big impact on the aquatic ecosystem of the lake and therefore on the organisms that live in them. The temperature of the water varies between a range of 16.4°C and 31.2°C with changing climatic conditions. The lake’s temperature determines how much organic matter gets decomposed in the water because it controls the activity of bacteria.
Often strolling around the lake or sitting on its edge, one can enjoy the dazzling skyline and in the backdrop Ajmer’s famous Daulatbagh gardens and Baradari (pavilions). An island is located in the middle of the lake; tourists can hire boats or water scooters from the east side of the Daulat Bagh Gardens to reach the island.
The lake is located in the northwest area of Ajmer (74038’ – 74042’E and 26025’ – 26029’ N) with a gross catchment area of 56 sq. km; 20 sq. km intercepted by Foyasagar and 5 sq. km of built-up area. The nature of the lake’s catchment area is steep to a gentle slope with low vegetal cover. The lake has a storage capacity of 4.75 million cubic metres and has a maximum depth of 4.4 metres. The circumference of the lake is 4.81 km. It also has a water overflow arrangement with four overflow gates of size 4’ X 6’.
pH: The maximum and minimum values of 8.9 and 7.3 were recorded in the lake water. These pH values are in accordance with Wetzel’s earlier work, which reported that the value of pH ranges from 8 to 9 in Indian waters.
Dissolved Oxygen: In 2007-2008 the DO level in the lake had dropped to almost negligible levels. The situation is now under control as the outflow channel gates were raised, as a result, the dissolved oxygen in the lake has improved.
Nitrates: Nitrogen is essential for all living things, but its high presence leads to significant water quality problems. It had been examined that the lake had minimum and maximum nitrate concentrations of 10.1 mg/L and 17.8 mg/L.
Chloride: Chloride in water is known to increase its corrosivity. Metal pipes get corroded, and lead pipes that are coated with an oxide layer, albeit a thin one, are also corroded as they increase galvanic corrosion. The observed values fell into the range 430-590 mg/l with an average of 510 mg/l.
Salinity and Electrical Conductivity: The water in the lake is slightly salty, and the average value has been noted above 1000 ppm and ranged from 1400-1700 ppm. In Anasagar, the value of electrical conductivity is measured at between 2140 to 3500 µmho/cm, which is another indicator that the water is not safe for drinking as potable water generally has conductivity values ranging from 50 to 1500 µmho/cm.
The following recommendations can help to maintain the eco-sensitive zone:
Vigilance on washing clothes: A campaign should be run to raise public awareness on the importance of not washing clothes and putting harmful detergents in the lake which severely affects water quality. The local government should also set up a prevention and improvement team and ask the locals to stop washing clothes in the lake.
Proper arrangement for garbage disposal: A lot of times people dumped their garbage into the lake that caused the water to become dirty and unhygienic and led to the spread of numerous illnesses. Simply educating people about not throwing trash into the lake is not enough. In order to find a solution, the concerned authorities need to conduct special education on proper garbage disposal as well as the proper ways for keeping the lake clean.
Prevent Sewage Water from contaminating the Lake: The sewage water is a great pollutant for the lake, still, people often drain their sewage water directly into the lake which contaminates it and makes it unhealthy for the living beings residing in the water. Proper efforts should be made to stop sewage discharge so that the lake remains healthy and fish swimming in it remains safe to consume.
Regular cleaning: Lake cleaning is essential for most of the water. With the regular cleaning of the lake, its water and all aquatic lives living in the lake remain in good health, thus making the lake more healthy. The toxic sludge from the lake water should be filtered out of all of the solid waste products.
Developing Water Sports Infrastructures: Tourists often get attracted by water sports activities and such recreational ventures boost the tourism of any destination. By introducing these activities, the tourists may be lured to visit the lake which may generate revenue that can be used to maintain the lake and its surroundings.
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