Unit - 5

Water Distribution system, Rain water Harvesting and GIS

5.1 Water distribution system:

• The beginning of the water distribution system is the end of the water treatment plant. After the purification of water, it is supplied through the pipe lines to the individual houses, industrial units and to the public places with a given pressure and in a given required quantities
• This distribution system has a number of components like balancing reservoirs pipes of various sizes, control values, pumps meters and hydrants. On the basis of the topography of the region and read-network the water distribution system is prepared.
• While preparing such plan, all the details about the location of pumps and pumping stations, balancing reservoirs, position of valves, street mains and the hydrants, must be marked; to have the correct execution of the plan.

5.2 System of water supply:

The basic requirements of the distribution system are

• The quality of water must be maintained. Each consumer must get required quantity of water with the desired pressure.
• The distribution system must be economical.
• The maintenance cost should be less.
• The adequate water must be made available to put out an emergency fire.
• The repairing or replacing work of the distribution system should not cause obstruction to the road traffic.
• The pipes carrying the drinking water must be laid at least one metre away or above the sewer lines.
• The leakage at the joints must be minimum.

Objectives of Good Distribution System:

• Design of the water distribution system with the following objectives
• It must convey the water to the point of need, from the treatment plant.
• It must maintain the quality of water from to plant to the actual users.
• It must ensure the supply of water with sufficient pressure and quantity at all the places, during all the times.
• It must have the arrangement to provide water to meet the emergency like fire. It must be a reliable service.
• As the water distribution system covers about 40% to 70% of the total cost of the water supply scheme, it is necessary to have correct planning for the distribution system.

5.3 Continuous System:

• In this, the water supply is available throughout the day Le all 24 hours, with no break. It is possible in a region where ample water is available.
• It is the best method to keep the water clean and fresh as the water does not become stagnant at any time in the supply pipes, giving no chance of getting distribute impurities; but it can create a greater loss of water as people do not bother to save water, due to easy availability.
• It is not economical method.

5.4 Intermittent System:

• The water supply is controlled by providing it during the fixed hours of the day. e.g., 2 to 3 hours in the morning and 2 to 3 hours in the evening. This system is used when there is a shortage of water supply or there is problem of maintaining the pressure required for the flow of water through the pipes.
• In large settlement the water supply is controlled by following the rotation method e.g. 'A' block may get water from 4 a.m. To 6 a.m. 'B' Block may get the water from 6.15 to 8.15 am and so on.
• This system is economical and eco-friendly also. In India, this system is commonly used.

5.5 Different distribution systems:

Gravitational System

• In this the water flows from the source region to the treatment plant and from the treatment plant to the distribution centre, by gravity, by taking the advantage of the sloping of the terrain, it is a reliable and low-cost system.

Direct Pumping

• In this, the water is pumped from the source to the treatment plant and from the treatment plant to the distribution centre.

Combined System

• In this both the gravity and the pumping methods are combined, wherever required. Among these three methods of water supply the gravitational system is cheap but it is difficult to maintain the water pressure.
• In the direct pumping system, the pressure and quantity of water can be maintained but it is costly, it fails when the power supply (electricity) fails.
• The water pressure has a lot of fluctuation at the consumes end. So, if both the systems are put together, the combined water supply scheme gets the advantages which are as follows:

1. The pumps can work at a given convenient schedule.
2. The required pressure can be maintained during the water supply.
3. When the power fails, the advantage of gravity flow can be taken for the water supply.
4. The quality of water improves due to the period of detention, in the elevated reservoir.

5.6 Components of distribution system:

1. Valves

e.g., Air Valves, check valves, scour valves, sluice valves.

2.     Fire Hydrants

e.g. (i) Flush type fire hydrant (ii)Post type fire hydrant.

The hydrants are used to withdraw water from the mains or sub mains, during fires.

3.     Water Meters

They are used to measure the quantity of water supplied through the pipes to each connection, on the basis of accuracy requirement, two types of meters are used.

• Displacement or positive meters.
• Inferential or velocity meters.

4.     Service Pipe Connections

To supply the water to the consumer from the feeder line of the distribution system, these service pipes are used. Depending upon the requirement these services pipes, with different diameters, e.g., 15, 25, 40 mm diameter pipes are used.

5.     House Fittings

For the proper distribution of water in the house proper fitting are required. e.g., Tee, Cross, Wye, Union, Plug, Socket, elbow, nipple etc.

6.     Water Taps and Cocks

As per the used and requirement different taps and cocks are used for the water flow and control. e.g., A: Stop Cock, B: Bits Cock.

5.7 Elevated Service Reservoirs (ESR)

Definition:

• The reservoirs which are constructed at an elevation from ground level are known as Elevated Service Reservoirs (ESR).

Function of ESR

• Elevated tanks are constructed to supply water under gravity. They also balance the fluctuations in demand and supply.
• They also supply water during emergency.

Fig. 1: ESR

5.8 Design of ESR capacity:

Following are the various design criteria for finding the storage capacity of an elevated storage reservoir (ESR)

1. If the reserve storage is elevated the amount of fire reserve can be calculated from the following expression.

R = |F - P| T

Where R = Reserve storage in litres

F = Fire demand in lit/min

P = Reserve fire pumping capacity in lit/min Duration

T = Duration of fire in minutes

2.     McDonald has suggested the expression by which storage capacity of reservoirs can be determined

R = aD + bD + 10/24 * (D + F - P)

Where, R = Total storage capacity in million litres (ML)

a and b = Coefficients (Value of a = 0.2 and value of b=0.1)

D = Average domestic demand (MLD) for maximum month

F = Fire demand (MLD)

P = Capacity of pump (MLD)

3.     In case of a storage or distribution reservoir is designed for the purpose of balancing or equalizing the flow, its storage capacity may be calculated by three methods as follows:

a)     Hydrograph method

b)    Mass curve method

c)     Analytical method

5.9 Wastage and leakage of water: detection

Following techniques are used for leakage detection.

a)     Finding leakage in shower

b)    Emerging technology

c)     Use of ground water

1. Finding leakage in shower pipes by Gas

By using the hydrogen gas system, the leakage can be detected and can be corrected. It is useful for domestic leakages.

2.     Emerging Technology

Recently an advanced form of leak localizer has been put in use. A surface sensor array is used to detect the leakage. This instrument sends a radio frequency carrier signal into the ground and it detects the leakage.

3.     Use of Ground Radar

It is a device, which is primarily used to locate the pipes and other buried objects. The water leakage can be found through observing the disturbed ground or cavities around the pipes. It can locate the leaks, where leak noise correction is not possible due to noise developed by pumps and valves.

5.10 Leakage prevention system:

• To detect the leakage of water and to repair such leakages, as early as possible, is one of the fundamental components of water conservation
• Any type of loss of water is always an important issue but when such losses cause the loss of the treated water to be used for consumption, the problem becomes serious
• There are mainly reasons for the water leakages, e.g., old or poorly constructed pipe lines inadequate corrosion protection, poorly maintained valves and joints and any type of mechanical damage etc.
• An accurate location and repair of such leakaging water pipes, in the supply system greatly reduces the water losses.
• Before the repairs of the leakages are to be made, we must observe the signs of the underground leakages which are as mentioned below.

A: Unusual wet spots in the land scape areas and water pooling on the ground surface.

B: A notable drop in water pressure and in flow volume.

C: A sudden supply rusty water.

D: Development of sinkholes.

E: Unexpected and sudden increase in water demand. We already discussed about the methods used to detect the leakages.

• It has been found that large leakages do no
• It constitutes the greater volume of lost water mainly if the water reaches the surface where they are usually found quickly can be Isolate and repaired.
• However, the underground leakages, may be small in size can lead to a larger loss of water.
• To detect a leakage is only the first step in eliminating leakage. The leakage repair is the more costly step in this process.
• There are two views, about the methods of preventing the leakages.

a) Repair the old pipes having leakages.

b) Replace the old pipes to stop the leakages.

• The method to be applied to stop the water leakages depends upon site-specific leakage rates and on the cost, of repair or the cost of the replacement.
• The leakage detection and repair result in an immediate reduction in lost water.
• The replacement of pipes will have a longer lasting impact to the extent that it eliminates the root cause of leakages.
• To control the problems related to the water supply system the better way is to have regular checking of the flow of water and to note the water supplied from the main and water received at the consumers point and to have regular maintenance of the water carrying pipelines.

5.11 Rainwater harvesting: introduction

Introduction:

• The crisis of drought is the non-availability of consumptive water and also non-consumptive water i.e., water we need for domestic, agricultural and industrial use and the water in the dam-reservoirs is also made available hydel power generation.
• If the rains are late or inadequate, the surface run off, rate of infiltration is reduced to there is shortage surface water and ground water to create severe drought conditions.
• To control the end product, it is necessary to harvest the water (save it for a non-rainy day or non-rainy year). This can be done by following the methods mentioned below.

5.12 Need of rainwater harvesting:

• Rainfall is the first form of water we receive from the hydrological cycle.
• The rainfall is the primary source of water (to be used for various purposes as stated above).
• The rainfall supplies water to the surface in the form of lakes and ponds to the surface runoff in the form of streams and rivers and to ground in the form of water table.
• So, the rivers lakes and underground water are the secondary sources of water.
• We always leave the primary source of water i.e., rainfall, without any botheration and try to make maximum use of the secondary source, which is not 100% of the potential water of rainfall as part of it is sent back to the atmosphere through evaporation.
• So, to make maximum use of water, we must try to collect, at the source. So, rainwater harvesting is the best possible method to conserve the water for better use.

5.13 Method and components of domestic rainwater harvesting system:

Methods of rainwater harvesting:

1. To capture the runoff (rainfall) from the Rooftop (at the first receipt point).
2. To capture the runoff from the local catchments i.e., water-shed areas.
3. To capture the seasonal flood-water of the surface streams.
4. To conserve the water through better utilization of modem irrigation systems like drip irrigation or sprinklers etc. (to conserve is to have best possible use with minimum wastage)

These techniques or the methods can serve the following purposes.

Components of domestic rainwater harvesting system:

a)     Catchment

The surface which receives the rainfall e.g. The roof of the building.

b)    Coarse mesh

It prevents the passage of debris. It is provided on the roofs.

c)     Gutters

They are the channels which surrounds the edge of the sloping root. They collect and transport i.e., rainwater to the storage tank.

d)    Conduits

They are the pipelines or drains, which carry the rainwater from the roof or the catchment.

e)     First flushing

It is valve, which does the work of flushing out of the 1" spell of rain water, having a large amount of pollutants from the surface of the root. Filters They remove the suspended matter which may pollute the water.

f)       Storage facility

The storage tanks of various shapes and sizes are used to collect and supply water for various purposes. If the rain harvesting is carried to recharge the ground water, mainly in the rural areas, the water collected from the root is used to recharge the ground water level, through the dug well, bore well or a pit.

5.14 Design of roof top rainwater harvesting system:

• For the design rainwater harvesting (RWH), Size of water tank play a vital role; hence main part is to determine the size of the water tank correctly so as to have adequate storage capacity.

• Following are the various parameters considered in design of RWH:

1. Requirement of local rainfall data.
2. Weather condition
3. Requirement of roof collection data
4. Number of users (N) and their water consumption rate.
5. Runoff coefficient (0.5-0.9)

(Depending upon the slope of roof and its material, the runoff coefficient various between 0.5 to 0.9)

6.     RWH system component and their size.

7.     Different methods for sizing the RWH system components and hence use the proper method for deciding the RWH components.

8.     Selection of the proper method to design the system components depends upon the following parameters.

a)     The size of the RWH system

b)    The size of the RWH system components

c)     Expert their experience and level of education for proper design.

d)    Availability of tools needed for employing the particular method.

9.     Methods for sizing rainwater harvesting. There are specially two methods used for sizing the RWH.

a)     Demand size approach

b)    Supply side approach

1. Demand size approach

• It is very simple methods and more useful to the compute storage requirements in which the water consumption rate and occupancy of the building has prime importance.

Data required for this method

1. Consumption per capita per day (C)
2. Number of persons per house (N).
3. Largest average dry period (T)
4. Annual consumption = CN365
5. Storage requirement (S)

S = CN

2. Supply side approach

• This method is more suitable in the region where rainfall is low and uneven and due to this; a proper care should be taken to find the size of storage tank. Following are the various parameters to be considered design the RWH.

a) Quantity of rain water in a year

In this case, during some month of year; there may be excess of water and sometimes, there is deficit. Hence note that if there is sufficient rain water throughout the year so as to fulfil the required demand, then and then only sufficient storage will be used for the periods of scarcity.

Hence design of storage tank should be done more carefully so as to avoid expense on tank because structure of storage tank is expensive.

Qty of rain water in a year (V) = AXIXR

Where, A = Area of roof or terrace

1 = Average annual rainfall

R = Runoff coefficient

b) Storage capacity of tank (V')

V' = AxIxR

Where,

I = Number of rainfall days

R= Coefficient of runoff

c) Dimension of tank:

V' = Axd, Where d= depth of tank

5.15 Use of GIS and drone technology in water management:

• Water, that is a crucial valuable, finite, renewable and shared useful resource demanded through numerous sectors, ought to be controlled optimally. The pressure because of unavailability or confined availability of water is developing at alarming rate.

• Irrigation region is the largest patron of water as extra than 80% of to be had water assets in India are being currently applied for irrigation purpose, serving at simply 25 to 40 % water use performance. Therefore, it's far vital to enhance the irrigation and water use performance for buying most yield.

• Drones are gambling a growing function in fixing troubles in agriculture and irrigation management. The use of Unmanned Aerial Vehicles (UAVs), additionally referred to as drones, and linked analytics has terrific ability to help and cope with a number of the maximum urgent issues confronted through agriculture in phrases of get right of entry to actionable real-time great data.

• Goldman Sachs predicts that the agriculture region may be the second one biggest consumer of drones withinside the global withinside the subsequent 5 years. This paper affords a case examine of use of Drone for mapping of command vicinity of irrigation task in Pune place of Maharashtra State of India.

• The interest of drone survey became achieved on approximately 500,000 ha vicinity. The goal of drone survey became to perceive the crop sensible vicinity and the usage of this records education of announcement of water charges.

• The final results of drone survey led to correct estimation of vicinity irrigated and correct identity of crops. This helped branch officers in saving in time and elevated revenue. This method brings transparency as drone snap shots are preserved and may be verified.

5.16 Source, treatment and distribution:

• The primary unit in water assets control is the river basin or hydrographic catchment, and the community of draining channels, the river community that collects and conveys floor water.

• River reaches, dams and reservoirs, diversion and pumping stations, water works and secondary distribution networks are all spatially disbursed factors of this system. Underneath, we discover the unsaturated and saturated zones of groundwater aquifers, commonly contributing large portions of excessive first-class water with pretty one of a kind, an awful lot slower garage and go with the drift traits.

• The factors of water assets control are disbursed in space. Their location, surrounding, and spatial relationships are vital for the ensuing go with the drift traits and the first-class, of the water assets and for that reason their availability for one of a kind forms of use. River basin control has apparent spatial dimensions, considering its miles targeted on a spatial unit, the hydrological catchment, withinside the first place.

• Consequently, geographic records structures are one of the equipment that may be used for his or her evaluation. This makes the usage of GIS, and its integration with conventional water assets fashions, and apparent approach for the improvement of river basin control structures (Maidment 1996, Fedra and Jamieson, 1996).
• While the GIS is used to capture, analyse, and show spatial information, the fashions offer the equipment for complicated and dynamic evaluation. Input for spatially distributes fashions, in addition to their output, may be handled as map overlays and topical maps (Fedra,1994).

• The acquainted layout of maps helps the expertise of version effects, however presents additionally a handy interface to spatially referenced information. And professional structures, simulation and optimization fashions upload the opportunity for complicated, and dynamic evaluation to the GIS. One main project in constructing powerful river basin records structures is the mixing of dynamic fashions with the skills of GIS.

• The GIS can offer a not unusual place framework of reference for the diverse equipment and fashions addressing a number issues in river basin control, deliver disbursed information to the fashions, and help withinside the visualization of spatial version effects withinside the shape of topical maps. In a multi-media framework, it may additionally offer a not unusual place interface to the diverse features of an incorporated river basin records and choice guide system.

• This interface has to translate the information and version capability to be had into records that could at once guide choice making processes (Fedra, 1995).

• The water resources model needs river flow at all of its start nodes, representing inputs. These can be well fields, where groundwater enters the surface water budget, or sub-catchments. For the latter, a rainfall-runoff model provides data for ungagged catchments, but also the possibility for scenario analysis of land-use changes or long-term climate change. Data such as catchment boundaries, elevations and slopes, land use, as well as rainfall inputs are automatically taken from the GIS and time series data base, respectively.

References:

1. Environmental Engineering, Peavy and Rowe, McGraw Hill Publication
2. Optimal Design of Water Distribution Networks, P.R. Bhave, Narosa Publishing House
3. Rain Water Harvesting: Making water Every Bodys business, vcentre for science and Environment
4. Environmental Remote sensing from Regional to global Scales, Ed. Giles Foody, Wiley
5. Water supply Engineering, Harold FatonBabbit & James Joseph Doland, Tata McGraw Hill
6. Environmental Engineering Laboratory Manual and Dr. N. Kumarswamy. NEERI, Nagpur