Planning of
Water Supply
A water
supply project generally consists of a water collection unit, conveyance
system, and units for treatment, purification, and distribution. It is
necessary to plan, prepare, and design the entire water supply scheme before
constructing the units. A proper plan will ensure that an efficient and
economical system is finalized with minimum expenses. The scheme should be such
that it can be constructed within the allotted budget while permitting future
expansion.
1. Data
Collection
Before
planning for the water supply project, the following data have to be collected:
1.1 Hydrological Data
Hydrological
data gives an overview of the long-term monitoring of the water sources that
exist in the vicinity. The data will help in estimating the total availability
of surface water.
1.2 Geological Data
The
geological data will help in understanding the rock composition and other
aspects of the ground surface. This will help in estimating the availability of
land.
1.3 Water Requirement of
the City
It is
necessary to know the population count and its water needs. In case there is an
industry in the vicinity, information regarding its water requirements also
need to be found out. The current water demand and future requirements can be
forecasted with this data.
1.4 Existing Water Supply
Projects
The data
on existing water supply projects in the vicinity will help determine the
additional net availability of water. Moreover, the extra requirement of water
can be calculated.
1.5 Sanitary Conditions
of the Area
Along
with the data on the sanitary conditions of the area, other sources of
pollution must also be known. In case there is contamination of water due to
multiple sources such as industries, factories, etc., then the cause should be
identified, and remedial measures should be taken for the same.
1.6 Topography of the
Area
This
information is very important as it will highlight the low-lying areas and
ridges concerning the available source, population density, etc. The intakes,
treatment works, and distribution reservoirs can then be planned accordingly by
considering an economic conveyance system.
1.7 Legal Data
The legal
data is essential to stay out of any legal issues involving water rights, land
ownership, land zoning, clearances, etc. The land options should be evaluated
and the location with minimum legal approvals would pose as an ideal location
for setting up the treatment plant.
1.8 Public Opinion
The
public opinion will not only help in counteracting the claims of the government
in an event of dispute regarding land acquisition, but also be helpful while
seeking expenditure sanctions and approvals from the authorities.
2. Project
Formulation
Once all
the necessary data has been collected, it should be analyzed and the future
needs must be evaluated. The following activities should be carried out in the
project formulation stage:
- Estimation
of the population trend for the present and future based on the local
conditions to identify the quantity of water required to be fulfilled by
the project.
- Locating
a reliable source(s) of water so that all the demands of the community are
met.
- If
needed, make provisions for the storage of water and design the system
required to transmit the water from its source to the consumers.
- Determination
of the characteristics (physical, chemical, and biological) of the
available water.
- If
needed, design the water treatment facility to improve water quality up to
the standard of potable water.
- Design
the layout and units of the distribution system. It must include pumping
stations, storage facility, size of pipes, fire hydrants, valves, and
other important details.
- Make provisions for the
establishment of an organization to look after, maintain, and operate the
units after construction.
3. Project
Drawings
Drawings
are a crucial part of the project as the entire plan and design of the
components of the project are expressed by it. The following drawings are
generally prepared and used for execution purposes:
3.1 Topographical Map
The
topographical map shows the features of the area and includes sources of
supply, roads, etc. In certain maps, the layout of the pipes that convey water
from the source to the city may also be included. The scale of the map may be
1:500 or so.
3.2 Site Plan
A site
plan of the town showing the location of the scheme and the area to be served
by the scheme should be prepared. A scale of 1:500 may be used.
3.3 Contour Plan
A contour
plan is essential as it shows the location of the water main, sub-mains,
valves, branches, hydrants, pumping stations, etc. Sometimes, the contour plan
and the site plan are combined to form one plan.
3.4 Flow Diagrams
The flow
diagram includes the line plan and section and also shows the sequence of
operations.
3.5 Detailed Drawing
Detailed
drawings include components and units along with their dimensions and both
structural and hydraulic details. The drawing should include different sections
of the mains and branches, treatment units, etc.
4. Project Estimates
A
preliminary estimate can be prepared once the preliminary drawings are made. It
will give a tentative idea about the cost, and the same can be communicated to
the authorities for seeking approval and sanctioning expenditure. In addition
to the cost of the components and units of the system, the rough estimate must
also include the cost of pump houses, staff quarters, etc. The tentative costs
of the water supply system are given in Table-1.
|
Sl. No. |
Component item |
Cost of the item (%) |
|
1 |
Pumping stations |
18 |
|
2 |
Distribution system |
50 |
|
3 |
Treatment plant |
10 |
|
4 |
Supply penstock |
9 |
|
5 |
Reservoirs |
6 |
|
6 |
Buildings for housing operational
staff, etc. |
2 |
|
7 |
Meter and other contingencies |
5 |
|
|
Total |
100% |
Table-1: Tentative costs (%) of the
water supply system
After the
formalities regarding the project approvals are completed, the detailed drawing
and estimates are to be prepared. On obtaining the administrative approval, the
competent authority of the concerned engineering department will sanction the
estimate. After that, the bidding procedure for the execution of work can be
carried out.
5. Project Reports
The
project estimates and the drawings should always be supported by a report. It
should justify the necessity of the project, the economic feasibility along
with the benefits, and must have the pros and cons of any alternative
proposals, the actual designs, proposed water rates, etc.