D G Sonwane
Deputy Chief Engineer (Civil)
TCE Consulting Engineers Ltd, India
|In order to improve the infrastructure and the quality of life of Jodhpur citizens major development works were initiated by the Government of Rajasthan. This paper describes the project done to study the city’s water and wastewater systems for improving the existing system and extending the services in unserved areas|
Jodhpur, the second largest city of Rajasthan and main focal point of tourism and industry, has experienced a rapid growth in the last decade. Geographically, it is located at 26o N 18′ latitude and 73o E 02′ and at an average altitude of 240m above mean sea level. In general the contours are falling from North to South and from North to Southeast with maximum level of 370m and minimum of 210m. The topography of the city is such that the water transmission to the city is by pumping and sewerage system by gravity. The present population is about 0.86 million and admeasures 230 sq km. The projected population in 2034 is 1.772 million.
Water Supply Component
The planned water supply to the Jodhpur city dates back to the year 1886 and has been augmented many times. At present, the city receives water from Rajiv Gandhi Lift Canal (RGLC). The raw water from the RGLC is stored into two impounding reservoirs called Kailana and Takhat Sagar. There are three major water supply zones in the city, which are based on water treatment plants located in Kailana, Chopasni, and Jhalamand. The total quantity of the water supply is 141 Mld with approximately 18 Mld being supplied to industries and other domestic use. The remaining 123 Mld is supplied to the city for distribution, resulting in 115 liters per capita per day (lpcd).
Existing Distribution System
The three major water supply zones are further subdivided into 33 small subzones, which are supplied through either individual reservoirs or direct tappings on transmission mains. Some of the systems most challenging problems include low pressure at terminal ends and uneven distribution of water. At tail ends, the pressure is of the order of 1m to 3m. The duration of supply is less for two to three hours a day. With supply far short of the projected growth in population, there is an urgency to extend the water supply to newly populated areas, which are presently served by water tankers.
Proposed Distribution System
To bring the unserved areas within the purview of water supply and to make the equitable water distribution with adequate terminal pressures, additional water distribution works have been identified and proposed under this package. The additional storage requirement has been covered separately.
The distribution system planning was done to utilize the advantage of the topography of the city and existing facilities to full extent. The new distribution zones have been formed, which are mainly new habitations, and the farther areas of existing distribution zones. The zonal boundary has been marked based on the capacity of the existing reservoirs with respect to the projected population and the area it can serve, topography, and the location of proposed reservoirs. New zones have been proposed for 22 areas and the distribution system has been analyzed using Haestad Methods’ WaterCAD software package for water distribution system modeling.
Water Demand for Distribution Zones
There are 60 wards in the city. Ward wise population projections have been made and the water demand is worked out using 135 lpcd for urban population and 70 lpcd for supply through public stand posts for the years 2011 and 2034 being the design horizons. Consideration has been given to non-domestic consumption type locations such as hotels, cinema halls, and bulk supplies. The losses incurred by water treatment plants, transmission, and distribution systems are added to arrive at a gross demand at the source level. For each water distribution zone, the fraction of ward contributing to that zone is assessed based on zonal boundary and ward boundary. Water demands for each zone have been calculated depending upon the population of all fractional wards, with complete wards coming under a particular zone. The zonal demands are reduced by 2% and 3% to account for the transmission and treatment losses respectively in a uniform manner. The reduced demand for each zone is distributed among the nodes considered for design as per layout of the network. The nodal demands are calculated in proportion to the length of each pipe and additional demands are added for nodes expected to have more population growth on account of present open areas and population growth pattern. Industrial demand is also added to junctions based on the locations of industries.