Hydro Geology - Water Supply System - Assessment Answer

Hydro Geology Assignment

Assignment Task

WATER SUPPLY SYSTEM

Introduction

A water supply system is a system of collection, transmission, treatment, storage and distribution of water among consumers and source for instance homes, commercial establishments, industries, irrigation fertilities and other public users. The amount must be of good quality and quantity. There is an increase in water demand for domestic use and industrial areas. Sustainable water supply is more important and needs for the development of a system that will curb future uncertainties. A long-term water supply system will be required to ensure these risks are reduced.

Mudgee is a town found in Australia, central west of New South Wales (NSW). It lies on the edge of the Sydney basin. The climate is having a semi-arid characteristics with humid subtropical. The temperature during the night and winter is also cool. Rainfall is moderate and is received evenly across the months annually. The geographical inclination of Mudgee is relatively gentle meaning water may flow by gravity. The town was declared as a municipality in 1860; this makes it the second oldest city. The current population of Mudgee is about 10,000. A new university is to be established and will cater for 20,000 students. The establishment will need lectures and other support staff. It’s expected that the population of Mudgee will increase to 25,000 in 2020, and afterward grow by 5% rate per year.

Water is among the necessities of life. Our life is miserable without this precious commodity. We, therefore, have to uphold a high standard of water cleanness to ensure the water provided is free from pathogens. Lachlan River is the primary source of water in Mudgee. Often rainwater harvesting has been used to meet water demands of the area. The river levels keep on fluctuating due to climate changes and also high temperatures of the area. Ground water exploration has not been well utilized, and its use can relatively increase water quantity hence, meeting water demand.

Water supply requires high-level planning that will consider the current demand, future growth of population and also the available water supplies. The supply cost has the inclusion of capital for construction, operation, and maintenance. Water transportation to various households through truck is very expensive in the long run compared to piped water. The location of the storage facility should be centralized to ensure ease of movement; this also reduces the heat and frictional losses (Choi, Lim and Won, 2013, p. 19).

Ground water forms part of the hydrological cycle and forms 0.6% of the fresh water supply. Ground water is regarded as the readiest water source, meaning it is tapped directly from beneath the earth. The water is generally portable if no ground contamination occurs. Surface water is not much portable when compared to ground water, hence must be treated to make it portable. In ground water, not much can be done with the determination of the chemical quality of the water. This is because the water is extracted from much well-defined and sparse water-bearing geological strata (Kennedy, 2012). Mineral or chemical quality of water fetched from these water bearing aquifers will depend on the dissolution of the mineral in the aquifer. If the mineral is soluble, it will affect the water quality. The quality of water will be determined by doing an analysis of samples collected from these aquifers. The quality of water after the study will help in determining whether the water from the aquifer meets the required standards. Data from geologist and hydrologist will inform us on the probable usage of ground water from related aquifers. In different cases, ground water provides sufficient water for large communities or towns.

Problem Statement

Providing water sufficiently in the required quality and quantity has been a challenge over the year sand the most significant in human history. The construction of a water supply system that will cater for the entire population in an area has been a problem in almost all the principal towns. Water supply systems have structures that collect, stores, treats and distribute water from the source to consumers for instance homes, commercial establishments, industries, irrigation fertilities and other public users. The rapid population increase has affected the previously constructed water supply systems which will require future expansion. Water collected can be portable or non-portable uses depending on its quality. The structural system also has a new conveyance system and recharge facilities. Design water supply to cater for the future uncertainties is a problem. The climate changes and water demands fluctuate over the year this raises hardships in interpreting the systems. The construction of the university in Mudgee will increase the population due to students coming in from other states. Likely, the attraction of a new market, hence population increment. These problems will make water demand to increase. The town water supply is not designed for any future uncertainties.

Justification

Mudgee requires a proper water supply system that will cater for the future till 2070. Population increase being the main issue of concern creating a need for a water supply system. The proposed new university in this area with a capacity of 20,000 students will increase the water demand. These will lead to increase water demand, hence a design of an extensive water supply system will be viable.

Objectives

1. To design and test of performance a water supply system to make water accessible to the consumer.
2. To provide safe and wholesome portable water from ground water supplemented with rainwater.
3. To provide water in adequate quality

Scope

Follow the guideline that will be used in the initial stages of the design and the test of performance of the designed water supply system. The guidelines will also be in accordance with the water service authority of Mudgee. These guidelines will assist in setting objectives, development of the supply system and identifying the required procedures for design.

Literature review

Introduction

Water supply and distribution systems have a series of a network of pipes and all associated components. Most of these pipes are found underground where they are exposed to soil, hence surface traffic and also, internal water pressure buildup. Pipe failure disrupts water supply and limits the system. Proper inspection, control, and planning need to be addressed to ensure water loss is not due to pipe failures.

The water distribution system must be designed in such a way that it meets consumer demands and at sufficient pressures. The deign involves being specific about the elements of the distribution network. The pipe characteristics should be designed for the pressure and supply specifications needed (Banjac, Vašak and Baoti?, 2015, p. 958).

A least-coast water distribution network design. Optimum design needs to be determined with no regards to reliability. Reliability of the supply network is assessing, giving the minimum-cost of the water supply network design.

Gupta and Shrivastava applied Genetic Algorithm in the determination of optimal design of a distribution system and its rehabilitation. The water pipeline design problem and a real situation of a distribution network were analysed to demonstrate their project. (Gupta and Shrivastava, 2008, p. 93-96)

Evaluation of the minimal requirements of construction of a water supply system will be evaluated. The different types of supply systems, ways of harvesting water, sources of water. Various types of water supply systems and their working principles.

Sources of water

Water sources can be divided into classes according to the way or method of collection (Hunter, 2012)

Ground water sources

• Water from shallow wells
• Water from profound and artesian wells

Surface water sources

• Water from springs and seeps
• Rainwater harvesting from rooms
• Ponds and lakes
• Streams and rivers

Care should have to be taken during the initial identification of the source of water to be used, be it from the groundwater or surface sources. The selected water source should meet the needs of the service target group in sufficient quantity.

Overestimation of water supply sources is a common cause of the system failure. The task of identifying a proper source of ground or surface water should be done by a qualified professional hydrologist or geohydrologists. These professionals will determine if the water source can yield a sufficient amount of water to meet the water demand to be distributed now and in the future (Ermini, Ataoui and Qeraxhiu, 2015, p. 718).

Groundwater sources

Approximately 75% of the earth fresh water is locked out as ice, mostly in the polar ice caps. 24% is ground water, and the remaining 1% is represented fresh water storage on the surface and also the atmosphere. As seen the ground water exploration forms a proper underground water storage (Sharma, 2015, p. 578).

Groundwater is an important source of fresh water supply and is responsible for serving several communities. Groundwater prospection in many cases has a low construction, operation, and maintenance when compared to dams and water treatment works. If water sources like rivers and lakes are far, communities rely on groundwater (De Silva et al., 1999, p. 333-348).

Ground water is mostly stored in porous underground layers known as aquifers. These aquifers have connected fractures that act as a storage of water and will yield water in sufficient amounts. Aquifers layers can be of two types the primary and secondary aquifers and further classified as i) confined aquifer, these are those that are between two impervious layers. Water in this aquifer will tend to be under pressure. The water rise level in higher than the water struck level.

ii) Unconfined aquifer, this is a formation where the upper layer is identified by a water table that is under atmospheric pressure and the lower confining layer is an impervious stratum. This aquifer yields water in sufficient amounts for well to be placed. The water rise level in less than the water struck level

iii) Leaky aquifer, is a semi-confined aquifer that is, it has the properties of the confined and unconfined aquifer.

Ground water prospecting will tend to study the ground profile and the depth of each site where water can be found. The unconfined aquifer is the best where wells can be drilled because of it sufficient supply. Wells can either be shallow or deep wells. Shallow wells are dug to a depth less than 15m while deep wells go to depths beyond 15m.

Locating potential groundwater sources

Groundwater must be properly sited where there is a high penetration into the earth formation and where water is sufficient to supply a well. Maintenance and protection from surface contamination should be taken into consideration. Estimation of water quality is done because it's difficult to ascertain the quality of water in a given site. The planning for a water supply system in a particular area should be able to give quality water and also the consideration of present and future needs of this field. The water should be tested to ensure its free from coliform contamination or any surface contamination. Mostly, treatment of groundwater is not required De Silva et al., 1999, p. 333-348).

Geohydrological information is required before drilling any well. Geohydrological consists of information from the geological and hydrological data. Geological data can be of geological features like fractures dykes, fractures, and sills while geological formation is like the aquifers.

Hydrological data include that of rainfall, ground water recharge potential or the streams and lakes in that region. Geohydrology data can be obtained from the National Groundwater Database.

Groundwater development

Several methods are applied in the abstraction of groundwater. Depending on the soil characteristics of the area, the best method will be chosen to ensure efficient abstraction. Development of the site is required to ensure water safety. The preferred method should follow the necessary development techniques.

Methods for development of groundwater sources

Background of the wells

A well is an opening on the ground, then goes through an aquifer for water to be lifted out. The ground is dug out through different soil or rock layers until it reaches the aquifer and is partially full of water. For a proper design the following are to be considered (De Silva et al., 1999, p. 337-340).

• Correct design
• Proper construction
• Good development

A good well design of a water supply borehole should meet the following objective

• Sufficient high water yields and adequately protected from any contamination.
• The water in the borehole should remain sediment-free to protect pumps and prevent silting of the borehole.

The life of the borehole should be long. Material consideration in the design are the casing, well head, screen, filter pack, grout, silt trap, and annular seal. These are the essential good parts.

Design consideration of a well

A well head

It is a structure constructed at the ground level around the finished well casing. The main purpose of the wellhead to elevate the well to drain away surface water to prevent any contamination from coming into contact with the wall, also it prevents people or animals from falling into the well. The well head should be 0.15-0.20m

Well Casing

It’s a shell like perforated portion of the ground level down the aquifer of the well. It prevents the earth formation from collapsing into the wall, provides an open pathway to the aquifer, provides a proper housing for the pump, protects the ground water from interacting with shallow surface water and lastly, it’s a sealing zone for undesirable water. The design of the casing should take into account its diameter, material, and estimate of burial depth.

Well screen

It’s the perforated section of the casing and forms the intake section of the wall. The primary function is to allow free entry of water into the well, reduce the velocity of entry protecting the sides, safeguard the sides of earth pressure and give a proper good development. The length is considered from the aquifer thickness and also the available drawdown in the well.

Gravel pack

In an artificial gravel packed well, the aquifer material around the wheel is removed and replaced by a course material of higher permeability. It assists in increasing of permeability, excluding virtually of all formation material from coming into the well and to stabilize the well. The size of the gravel pack is about five times the diameter of the forming material.

Grout

The upper section of the annular space if often sealed with bentonite or cement/grout. These are to prevent contamination of well from the surface and prevent cases from collapsing.

Silt trap

The bottom of the borehole is left at least 6m of casing to allow setting of silt.

Rainwater water harvesting

Rainwater harvesting is the immediate collection of rainwater from a catchment excluding runoff from watersheds, rivers, streams, and lakes. Rainwater harvesting structures can be placed any suitable area (Memon, 2014, p. 13).

Roof catchment

Roof catchment is quite straightforward and inexpensive to construct. It's mostly used to supply water to individual homes. The material used in the construction is usually an impervious material such as tile or corrugated galvanized iron sheets. The conveyance system consists of a gutter and a downpipe, a storage tank and tap is connected to the reservoir for delivery. The storage can range from a small tank to large tanks placed on the ground level or beneath the earth’s surface. The water contains significant amounts of dirt and debris that was accumulated on the roof catchment. Treatment units need to be installed (Tjandraatmadja et al., 2013, p. 573).

Figure 2. Roof catchment collection

Treatment ensures water collected is of high quality.

Distribution

Once a source of water has been identified and well developed, a mechanism for distributing the water to the consumer should be applied. The design standards of Australian will apply in the design. Water services should be provided to everybody in the community. The pipeline needs to be properly laid to ensure water movements is not inhibited. Pumping should be employed where gravity flow of the water is not applicable (Nguyen and Han, 2014, p. 578).

Tanks should be contracted with the design capacity of water required. The storage can either be temporary or permanent. Permanent storage will be large because it stores water for a long time. Most of the roof catchment storage tanks utilize durable storage tanks since it has its design are done on the basis of annual rainfall in the area (Ermini, Ataoui and Qeraxhiu, 2015), p. 718.

Methodology

Assumptions

The well is already developed and the rainwater harvesting has already been placed as from the literature review.

Design period

The design period of the system after 2020 is 50 years.

Design Population

The current population is 10,000. University introduces 20,000 students. The future population is 25,000. Growth rate of 5%

Applying arithmetic progression for population forecasting

Pn=p+ ni

Where Pn – future population

P – present population

n – annual population increment

i – number of years

P=25,000+20,000=45,000

ni=45000×5100=2,250

Pn=45000+2250×50=157,500

The design population will be 157,500 in 2070

Water consumption rate

Water consumed per capita per day be 65l i.e. 65liters/capita/day from the state standards

water quantity Qliter=population ×consuption per capita

Q=157,500×65=10,237,500liters

Q=10,237,5001000=10,237.5m3

Maximum day consumption

maximum day consuption=1.5 ×day water usage

=1.5 ×10,237,500=15,356,250 l/d

Peak hour consumption

peak hour water consumption=2.25 ×day water usage

2.25×10,237,500=23,034,375 l/d

Maximum head loss

Assuming a maximum head loss of 10km

Design equation used

Design Equation Used:

Hazen Willia Equation is used to calculate the Head losses

HL = 10.65 (Q/C)1.85 L/(D)4.87

Where,

H = Head loss (m/km)

Q = Discharge (m/sec)

C = Roughness Coefficient

L = Length of pipe (m)

D = Diameter of pipe (m)

Firefighting

National board of fire underwriters

Qlmin=4637 P(1-0.01P

Where P is population in thousands

Q=4637157.5(1-0.01157.5)=50,890.6l/min

If lasting for two hours Q = 50890.6 x 60 x 2 = 6,106,872L

Total water demand

6,106,872 + 23,034,375= 29,141,247L

Therefor design using the hour peak consumption of 23,034,375l/d is appropriate.

Reservoir capacity

C=0.03 x D x T

Where C-tank capacity in m3

D- water total demand in L/d

T- Longest dry spell in months =

C = 0.03 x 29,141,247L x 3 = 2,622,712.23L + 6,106,872 = 8,729,584.23

Water will be stored near the site of the well and rainwater harvesting site.

Capacity= 8,729,584.23Litres

The depth of the tank = 6m

Compressive strength of concrete= M20

Free board= 0.2m

Diameter of bars used= 16mm

Designing two tanks connected in series for maintenance purposes capacity is divided by two

New capacity = 4,364,792.115L

V=?r2h

r=4,364.792115?x6=15.2m

Pump Specification

Friction factor is 0.03, velocity flow is 2m/s. Daily water requirement 29,141,247, working for 12 hours a day. Assuming a distance of 2000km and efficiency to be 80%

Q=29141.24712×60×60=0.674m3

v=QA=4qd2

d=4Q?v=4×0.674?×2=0.655 say 0.66

hf=flv22gd

hf=0.03x2000x222x9.81x0.66=18.5

Neglecting velocity head and other minor lose and assuming a head loss of 50m

H.P of a pump=QwH75n=0.674x1000x5075x0.8=560

Velocity and pressure

The maximum flows are 2.21m/Sec and minimum velocity of 0.33m/s

Maximum pressure in pipes being 20 and minimum being 15psia

Placing of valves

Valves are installed to regulate pressure, central pressure and also cut off the water supply. Two valves will be provided for each node and one for the fire hydrant.

Placement of the fire hydrant

For supplying water during fire emergencies, two lager outlets and its pump will be installed

Design of the distribution system

Loop programme

Loop computer program will be used for hydraulic simulation of looped water distribution network. The program utilizes Hardy Cross algorithm. It's limited to a maximum of 400 nodes, maximum of 500 pipes and can handle 10 nodes of known HGL

Inflow at node = outflow at the node

Required data for the program are the pipe number, node number diameter of pipe, pipe number and HWC of the pipe.

In return the program provides the head loss in pipes, the pressure at nodes, flow in pipes, the direction of flow and velocity in pipes.

Parameters of the software

1. Length in m
2. Diameter in mm
3. Flow in L/sec
4. Elevation in m
5. HGL in m
6. Head loss in me

A positive sign is assigned to inflow while negative to outflow

Procedure

• Draw the layout of the distribution system
• For each node represent it with a dot.
• Allocate the area with lots on each node.
• By using per capita consumption value, calculate water required at each node in litre/second
• By using of a trade paper of equal size to the map, trace the pipe and node network with it. Represent the nodes with a small circle.
• Number each pipe and node
• Measure lengths of the pipes according to the scale and record them.
• Write nodal flows in litres per second on the tracing sheet using arrowheads.

Pipe sizing

The pipe diameter will range from 8 inches at the source, sublaterals 4-inch house brunches 1 and 2 inch and ½ inch at the consumer.

Water delivered is 23,034,375 l/d, estimation of parametric reading at two sections, and length of a pipe to be used is known, the Hazen William formula will be applied to determine the diameter.

V=85m0.63i0.54

But v= Qd24

Therefore, the diameter will be calculated. Assuming the piezometric reading 8 and 10 at the two points. Water delivery = 23,034,375 l/d and length of pipe to be 900m. C is 100

Q= 23,034,3751000x24x60x60=0.267m3/s

i=10-8900=0.0022

Substituting Q=28.72.630.0230.54

0.267=28.7d2.630.00220.45=d=480mm

Figure 4: map showing design of main distribution pipes of Mudgee

Valves

The valve is placed after every 500m of pipe. All valves through the 8-inch pipe will shall be resilient seat gate valve in accordance with AWWA Standard C509.

Air release valves will be located at high points of the pipeline. For the 8inch pipe will require a 1-inch air valve.

Fire hydrants

They will be placed in interval across the distribution at intervals of 700m, and shall be installed behind the curb face at right angles to the water pipeline.

Conclusion

The project will ensure that the future is well protected from water shortages and all the population plus that of the new university is catered for. Construction of the tank and the distribution system was designed and well developed. The pipes and pressure of the distribution system are taken into consideration in relation to the pipe diameter