Provision of safe, adequate water is a basic necessity for the healthy living of a community. In this section, demand of potable water in the New Capital City Area has been dealt with. On the basis of the total water demand in different design years, identification of the water source, requirement of treatment
plant, and storage reservoirs have been estimated. Presently, the area is rural with ponds, small reservoirs and canals. It is also dotted with small to very
large water tanks, which are used by the villagers for ablutions, washing cattle and for irrigation. The Mahanadi Main Canal that runs along the western bank of the river principally feeds the extensive canal network in the New Capital City region.
10.1.1 Water Supply Norms Prescribed By CPHEEO
The per capita domestic requirements as per norms prescribed by Central Public Health and Environmental Engineering Organization (CPHEEO), Ministry of Urban Development, and Govt. of India are as under:
WATER SUPPLY NORMS FOR NAYA RAIPUR
Considering recommendations of CPHEEO Manual for Water Supply, Master Plan for Delhi 2001 and
Raipur Development Plan 2005, the following water supply norms have been adopted for the Naya
Residential areas 150 litres per capita per day
Commercial areas and Government Offices 70 litres per employee per day
Hotels 180 litres per bed per day
a. With beds more than 100 450 litres per bed per day
b. With beds less than 100 340 litres per bed per day
Institutional/ Industrial and Other areas 45,000 litres per hectare per day
Unaccounted Water 15% of total
Fire fighting demand 1% of total demand
10.1.2 Population Forecast
The population forecast for the years 2011, 2021 and 2031 have been shown in the table below:
10.1.3 Water Demand
Based on the above norms, the water demand for the Naya Raipur has been worked out. For Phase-wise
demand of water supply refer to table 10.3.
10.1.4 Water resources and availability
Following surface water resources are available in the area:
− Seonath River
− Mahanadi river
− Mahanadi Canal
Seonath River being seasonal is not considered as a dependable source.
Mahanadi River and Mahanadi Main Canal have perennial flow of water and are dependable sources.
− For the first phase requirement of water, Mahanadi Main Canal intake or Annicut construction
on Mahanadi River can be considered.
− For the water requirement in the second and the third phases, new barrage near Rajim may be
10.1.5 Water Treatment Plant
The canal water or water available from the proposed barrage on the Mahanadi River, after treatment, will be supplied to the city. The treatment will include screening, sedimentation, filtration, and disinfection, the level of treatment depending on quality of available water and permissible drinking water quality standards as specified by CHPEEO or WHO. Table 10.4 gives capacity of water treatment at different phases of development. It is suggested to construct the Water Treatment Plant (WTP) in different modules. Based on availability of water, location of WTP can be arranged in such a way that the cost of distribution system would be the least. The best location for WTP considering the general topography of the area lies near upstream side (near Khandwa dam, South Side of Naya Raipur), which has a high elevation. (Refer map 10.1)
10.1.6 Water transmission, Storage Reservoirs, and Distribution
The proposed water transmission system (raw as well as treated) is proposed to be operated for 20 hours in a day. The MBR at WTP is proposed to be of 6 hour capacity where as the sumps at individual pumping stations are proposed to be of 4 hours duration. The total system basically consists of two
1. Conveyance of raw water from the source to the proposed water treatment plants:
The raw water is proposed to be conveyed from the source to the proposed WTP through pumping
main, by locating head work and pumping station at suitable location..
2. Water from WTP after proper treatment will be supplied to different zones, for which the following
two systems are required:
• Transmission system from WTP to Various storage reservoirs
• Distribution system for various zones.
As per ascetic and landscape profile of the City it is proposed to use underground storage reservoirs and from these Under-Ground Reservoirs (UGR), Booster Pumping Stations can supply the water to distribution network. The concept of providing UGRs and BPS is a recent one and is in use in many metropolitan cities. The system has some obvious merits over the Over-head Tank (OHT) system as discussed under:
i. Economical in cost, construction in easy, requires low capital investments as compared to OHT systems.
ii. Space requirement is less as compared to OHT systems.
iii. Booster pumps can maintain uniform pressure in the distribution system.
iv. Water main need not be designed for excessive residual pressure as compared to OHT system.
v. This system is free of visual obstructions.
vi. These systems are entirely dependent on electricity. In Chhattisgarh has good power availability.However, the treated water sump in WTP is proposed at higher elevation in order to achieve water supply to various nodal points (reservoir locations) under gravity, gravity flow to the extent possible. However, where the minimum terminal pressure can not be met, combined pumping station(s) are proposed to supply treated water to the area through a pumping network. The diameter of pipe lines range between 300 mm. to 1500 mm. DI-k9 type pipes are proposed for dia upto 1000 m & MS pipes are proposed for higher dia.
10.2 Sewerage System
10.2.1 Sewage Generation
The sewage generation is approximately assumed to be 80 % of total net water supply has been considered out of which water supplied for green areas, washing streets, Horticulture, Fire fighting would cover the ground water infiltration. Refer to table 10.6 for phase-wise sewage generation in Naya
Considering the topography, the project area is proposed to be divided into two drainage districts, southern zone & northern zone, each of which is proposed to have an independent sewer network, pumping station & sewage treatment plant. The overall sewerage system is proposed as follows:
This zone is proposed to cater for 60 % of the total sewage generated in the project area; one STP is to be located at the lowest spot of southern zone. The exact location shall be determined by NRDA after conducting a feasibility study.
This zone is proposed to cater for 40 % of the total sewage generated in the project area, with proposed STP located in the area marked ‘zone I’as it is the lowest spot in the southern zone. An intermediate sewage pumping station is proposed in the area marked ‘planning unit II’, which would pump the sewage of about 50% of the northern zone into the trunk sewer leading to the STP. The diameter of branch sewers, trunk sewers, interceptiong sewers & outfall range between 450 mm to 1800 mm & the material proposed is RCNPIII. The rising main proposed is of DI-k9 type.
10.2.2 Sewage Pumping Stations
For sewerage system, Sewage Pumping Stations (SPS) are required where depth of excavation go beyond 6.5 m, based on the Natural contour and investigation made on general topography intermediate pumping stations are required for efficient and economical considerations.
10.2.3 Sewage Treatment
Sewage Treatment shall be done through Sewage Treatment Plant. The treatment based on Activated Sludge Process to be adopted. Two STPs of total 155 MLD capacity are proposed for Naya Raipur. The STPs shall be developed in modules in three phases. (Refer table 10.8). One STP shall be located in the north and the other in the southern zone outside the city boundary. (Refer map 10.2).
10.2.4 Disposal Options
The treated effluent shall be utilized in any of the following uses so as to conserve and minimize the overall water requirement viz., Irrigation, Horticulture, Ground water recharge. Three alternatives for the disposal of treated effluent are suggested as follows:
ii. 50% down stream of Mahanadi Main canal running parallel and in the ridge line and 50% to
iii. Other alternative is to reuse water for irrigation purposes for the downstream area so that net water requirement for irrigation canal (Mahanadi Main Canal) can be reduced. This is best possible alternative for efficient use of wastewater.
iv. Sewage after proper treatment and disinfections (not generally used for sewage treatment but required for effluent discharge Standards and DBU ‘Designated Best Use’ of Mahanadi Main Canal point of view) can be discharged to Mahanadi Main Canal. The Sewage treatment will be such that quality of water in Mahanadi Main Canal and treated sewage may not differ so much. In this case, a Pumping Station will be required to pump the treated sewage to Mahanadi Main Canal at suitable location to be decided after detail investigations.
10.3 Storm Water Drainage
Storm runoff is that portion of precipitation, which drains over ground surface. Estimation of such run off reaching storm water drainage system is therefore dependant on intensity and duration of precipitation, which again depends upon status of development of the area, soil and topographical characteristics and time required to reach the disposal points from the farthest points.
Drains are generally aligned along the valley lines between ridges. Only when natural drainage is not possible, drains are taken across the valley. The curves developed on rainfall intensity versus time of concentration showing 2-year frequency, 5-year frequency 10 year frequency and 50 year frequency in
the new capital is shown in Fig 10.1.
10.3.1 Storm Water Drainage For New Capital City
10.3.1.1 Issues and observations
Generally, the main issues on Storm Water drainage of this region are:
i. Inadequate provision of storm water drainage system.
ii. Lack of maintenance of existing drains and nallahs etc.
iii. Development process not compatible with drainage pattern.
The project area is traversed by four major streams thereby dividing the entire area into four catchment zones. All these streams are proposed to be preserved by carrying out rehabilitation/ improvements etc. All the proposed road side drains are proposed to convey the run off generated from the corresponding road and ultimately discharge the same into the corresponding nallahs / streams. Hence the proposed storm water drainage system for project area consists basically of two systems i.e.
i. Construction of Road side drains,
ii. Improvement or rehabilitation of existing Natural streams channels /nallahs.
• Road side Drains:
It is proposed to provide drains on both sides of the roads. Table 10.9 gives the length of various types of Roads suggested for New Capital city of Chhattisgarh. The storm water roads drains should as per guidelines mention in previous section. (Refer map 10.3).Rectangular concrete drains are proposed on either side of the road.
• Improvement of natural streams:
By the development of urban area, the coefficient of runoff will increase; hence, the existing section of streams will not be sufficient to cater the increased runoff resulting form Rainfall of selected frequency of occurrence. It is suggested to rehabilitate the existing drainage channel of new capital city of Chhattisgarh. 5 years Maximum rainfall intensity should be taken for design of system, similar to cities of international standards. Additionally cross drainage works are proposed at the road crossings.
The following policies are to be adopted:
i. Develop a storm water management system that manages the quality and quantity of storm water runoff of the region avoiding any water logging in the area.
ii. Recognize the need for public ownership and operation of storm water management practices such as rainwater harvesting.
iii. Prepare and adopt erosion and sediment control guidelines of the region.
10.3.2 Rain-Water Harvesting
Special emphasis is to be given to rainwater harvesting, in urban areas. Appropriate methods for recharging the ground water should be considered and adopted. Roof top rainwater harvesting at the individual as well as community level shall also be considered. Rain water storage, into dug up or natural lakes/ depressions, from the storm water drainage system shall be proposed, which will also help in environmental improvement as well as recreational uses.
10.3.2.1 Rain Water Harvesting for New Capital City
The principle of rainwater harvesting is to conserve and use precipitation in the same area where it occurs for greater ground water recharge and later use. The methods are site specific and may depend upon local conditions like check dams, roof top collection, aquifers recharge, storage in soil profile, creation of small basins in rural areas, contour binding, percolation tanks etc. due to urbanization in cities, the paved / impervious areas get increased resulting in reduced ground water recharge. Fig 10.2 shows common methods of Rainwater harvesting, which can be used in Naya Raipur. Rain Water Harvesting is mandatory at individual development level.
10.3.2.2 Storage Of Rainwater:
This can be achieved by following small-scale measures:
i. Recharge Pits for recharging the aquifers. These are generally 1 m wide and 2 to 3 m deep back filled with boulders, gravels and coarse sand.
ii. Trenches: Usually constructed when permeable strata are available at shallow depths. Trenches may be 0.5 m to 1 m wide and 1 to 1.5 m deep, 10 to 15 m long depending upon availability of water. These are back filled with filter material.
iii. Dug Wells: Existing dug wells can be utilized as recharge structures and water made to pass through filter media before putting into dug wells.
iv. Recharge wells: Recharge wells of 100 mm to 300 mm diameter are constructed for recharging the deeper aquifers and water is passed through filter media to avoid chock age of recharge well.
v. Roof top rain water: In big cities, roof top rainwater recharge has been recommended. Local authorities, communities need to be encouraged, can take up all these methods. Considering only 100 sqkm of area water harvesting and assuming average rainfall 1000 mm and assuming only 40 % average runoff to be retained by soil, the quantity of water that can possible be recharged may be around 40 Mcum.