Role of Hydraulic Modeling in Development of Road Map for Achieving 24x7 Continuous Water Supply in Old Water Supply Schemes

Dr. Pradip P. Kalbar[*]
Synergy Engineering and Environmental Solutions Pvt. Ltd., Thane
Mr. Vijay M. Kulkarni
Synergy Engineering and Environmental Solutions Pvt. Ltd., Thane
Mr. Pradeep N. Gokhale
Superintending Engineer (Retd.)
Maharashtra Jeevan Pradhikaran (MJP)

Abstract:

Present water supply schemes (WSS) in India operate intermittently and provide sub-optimal service to end-consumers.  There are efforts being made at all levels to convert intermittently operating WSS to 24x7 continuous water supply schemes.  In this study role of hydraulic modeling has been explained in achieving 24x7 WSS.  A clear road map for achieving 24x7 water supply has also been devised for old WSS operating intermittently.  The study reveals that there is critical role of hydraulic modeling in the development of road map for achieving 24x7 water supply. 

1.    Introduction

The increase in population and improvements in quality of life have led to a high demand for municipal and domestic needs. Demand for municipal drinking water needs will be driven by the rapid pace of urbanization and the high rate of per capita requirements for the urban population (70 - 135 LPCD[†]).  India’s urban population as presently defined will be close to 600 million by 2031, more than double that in 2001. Already the number of metropolitan cities with population of 1 million and above has increased from 35 in 2001 to 50 in 2011 and is expected to increase further to 87 by 2031(HPEC, 2011).  The focus of government departments has been to satisfy the present water demands of the city without giving full considerations to future demand.  Such kind of approach also lacks in integrated approach which shall include financial plan to sustain water supply scheme, improvement in operation of the project and other issues related to water quality and sanitation. 

In most of the cities in India, water supply is limited to 4 - 6 hours.  In a State like Maharashtra, the water supply schemes (WSS) have been designed and commissioned 25-30 years ago, at a norm of 70 LPCD of water supply for cities having no U/G sewerage scheme and 135 LPCD is for cities having U/G sewerage scheme, either existing or under process of sanction (CPHEEO Manual for Water Supply). For bigger townships, norm adopted may be even 150 LPCD. Over a period, the tremendous growth in population and urbanization and the negligence in operation and maintenance (O&M) of the water supply schemes have resulted in sub-optimal service of water supply in terms of both water quantity and quality. 

Present status of Water distribution systems in Indian towns:

1.    Water supply in most of the Indian towns, at present, is operated on intermittent basis, normally 2-3 hours in morning and 1-2 hours in evening. As water is supplied for limited hours, peak factor sometimes rises to 10-12 or even more as most of the pipelines are empty and lot of water is consumed in filling empty pipelines and reservoirs get emptied within a short time before water reaches to end consumers (Sashikumar et al., 2003),. Due to empty reservoirs, end consumers do not get desired pressure and hence, there is inequitable distribution of water.

2.    There are no DMAs formed and water distribution systems emerging from all reservoirs are interconnected and hence, coverage zone of each reservoir is not clearly defined.

3.    Most of the systems are not metered and hence, there is no control over consumers for optimum usage of water. Hence, consumers residing near reservoirs or in low-level zones, get more pressure, consume water in excess and end consumers or consumers residing at tail end pockets or in high-level zones do not get water as per minimum needs. Thus, supply is most inequitable.

4.    To overcome this problem to some extent, it is practiced to divide city distribution in different zones by providing control valves and bifurcating supply timings to control flow outgoing from reservoirs and possibility of empting of reservoirs. However, such attempt has no scientific standing and is based on experience of field staff. This also involves lot of valve operation twice a day. Moreover, control of such a system goes in hand of field staff not trained properly. In addition, public & political interference while operating such system may lead to more inequitable distribution of water. 

To overcome these problems, computerized analysis and scientific hydraulic modeling is necessary.  This study reports a general methodology followed for modeling WSSs.  Based on these modeling experiences a road map has been for achieving 24x7 water supply in old water supply schemes. 

2.    Methodology:

Water Distribution System (WDS) modeling is becoming more and more challenging owing to the increase in population, demand patterns and various types end-users.  Computer models are effective to handle the challenge of modeling and analyzing WDSs for different scenarios representing various demands, pipe materials, pipe sizes, etc.  In the computer models pressure and flow distribution is determined using laws of conservation of mass (implying that for each node the algebraic sum of flows must equal zero) and conservation of energy (implying that along each closed loop, the accumulated energy loss must be zero).  These laws of conservation either are expressed as nonlinear algebraic equations in terms of pressures (node formulation) or volumetric flow rates (loop and pipe formulation) which reflect the relationship between pipe flow rate and the pressure drop across its length.  The nonlinearity reflects the relationship between pipe flow rate and the pressure drop across its length. This nonlinearity in these equations leads to iterative numerical solutions for these equations.  The iteration process starts with assumptions of appropriate flow rates, which are repeatedly adjusted until the difference between two successive, iterates is within an acceptable tolerance (Mays, 2004). 

In this study Bentley’s Water GEMS V8i (SELECT series-2) version software has been used for modeling WDS.  For GIS maps, ESRI's ARC-VIEW and ARC-EDITOR software has been used. 

2.1  General methodology of hydraulic modeling

1.    Information of existing distribution system such as capacity, locations and levels of reservoirs, layout of existing feeder mains and distribution system with diameters, type of pipes and lengths is collected from available maps and also verified using GPS.  These maps are updated with information from distribution system operating staff and existing as well as recently laid pipelines are marked. 

2.    These maps and water network are now imported to Arc-GIS on satellite image of the town which is obtained from National Remote Sensing Agency (NRSA). 

3.    Information available from GIS and consumer survey activities such as present and projected population and water demand load on each junction is added to the shape file as attribute data. 

4.    Once the analysis in Arc-GIS is completed then the shape files (vector data) is imported in Water-GEMS. 

5.    Imported Network is validated and cross-checked for the accuracy.  New pipelines are proposed for areas not covered with existing network.

6.    Water demand for the base year is allocated to all the junctions in the network. 

7.    Now new hydraulically isolated zones (DMAs) are formulated considering future water demand for 15 and 30 years. 

8.    Considering base year water network as base scenario, new scenarios for future years and peak flows are created. 

9.    Based on the analysis in Water-GEMS zone wise demand as per existing network is estimated.

10.  Capacities of reservoirs are also checked for future demand for immediate stage of 15 years and ultimate stage of 30 years of each DMA and if capacity is found to be inadequate, additional reservoirs are proposed. 

11.  Now water network is analyzed for steady state to check the pressure at the junctions.  Areas of negative/low pressures or excessive pressures are marked and replacement of existing pipelines with higher/lower diameter pipelines or parallel pipelines and valve controls are proposed in such zones and network is again analyzed to get satisfactory output with adequate pressures in all zones to achieve equitable distribution.  If pressure is not sufficient, pipe diameters will be revised and again network will be analyzed to check junction pressures. 

12.  Finally water network is also simulated for extended period (EPS) of 24 hrs where impact of water level change in tank and reservoir is observed. Also, EPS helps in understanding the effects of changing water usage over time or the response of pumps and valves to system changes. 

13.  A water supply pattern (for 24 hrs.) based on, water habits of urban population in Indian cities is considered for analysis. 

14.  Based on the analysis recommendations are drafted suggesting physical and operational changes in the water network. 

Analysis in ArcGIS

Supporting Analysis

Check and rectify the attribute data

Population forecasting

Add population and demand attributes to Ward Boundary Layer

Import Vector Data

Estimation of ward wise demand

Estimation of ESR wise demand

Creating pumping schedule

Data Transfer

Hydraulic Modeling DPR

Recommendations

Analysis in WaterGEMS

Validation and Calibration

Zoning

Demand Allocation

Scenario and Alternative Creation

SS / EPS Analysis

Figure 1:  Flow chart showing methodology of Hydraulic Modeling

2.2  Modeling Existing scenarios

The existing scenario is created and analyzed for present actual consumption.  In this study the water network is modeled up to consumer end connections (refer to Figure 2) to simulate exact field conditions.  The actual demand exerted on each connection has been estimated using water audit study.  The result of steady state simulation is shown in Figure 3. 

Figure 2:  Water Distribution Network along with building polygons

Figure 3:   Water Distribution Network showing positive pressure (>12 m) almost at all junctions.

2.3  Modeling proposed scenarios

The proposed scenarios are modeled to check the suitability of existing network to cater to required demand and pressure for future years. Two stages (intermediate and ultimate) with 15 years of difference have been modeled.  A demand for these stages has been estimated from population projection data.  The adequacy of existing reservoirs is checked with respect to estimated projected demand for intermediate and ultimate stages. 

3.    Road Map for 24x7 water Supply

Based on the experience of modeling many WSSs a road map has been developed for transitioning to 24x7 water supply.  The road map has been segregated into various components such as pre-requisite for 24x7 water supply, stepwise approach for transitioning to 24x7 water supply and expected time frame for implementation. 

3.1  Pre-requisite for 24x7 water supply

There is an urgent need to convert the present intermittent water supply systems to 24x7 continuous water supply systems. Before undertaking transition to 24x7 it is essential to undertake comprehensive study of the existing water supply infrastructure. The studies shall include consumer survey, GIS mapping, computerized billing, hydraulic modeling, water audit and energy audit.  These studies will identify the present lacunae in the existing water supply system. 

1.    Consumer survey and GIS mapping will help in identifying all the legal and illegal connections.  The up to date consumer billing data can be fed to computer software specifically developed for billing and collection which will result in increase in revenue generation. 

2.    Hydraulic modeling is essential for checking adequacy of service reservoirs and pipes for delivering 24x7 water supplies.  New operating zones and DMAs will be formulated to deliver water at equitable pressure.  Such kind of engineered approach will help in designing a robust system for water supply with optimum investment. 

3.    Water audit identifies a DMA wise NRW in the system which enables development of priority wise action plan for addressing DMAs having high NRW.

4.    Energy audit helps identifying optimum investment in electrical equipments such that efficiency can be improved which will directly reduce the bill for the electricity. There can be many zero investment or low investment measures which will bring significant saving in the electricity bills of ULBs. 

5.    Ensure that all the ESR/GSRs have bulk flow meters at the inlet and outlet of the tank.  Also, bulk flow meters shall be installed at the inlet of all the operating zones and DMAs. 

3.2 Stepwise approach for transitioning to 24x7 water supply

Based on the above findings a detailed plan can be formulated for transitioning to 24x7 water supply.  The water supply scheme can be converted to 24x7 water supply using following stepwise approach:

1.    Select a pilot operating zone/DMA for undertaking transitioning to 24x7 water supply (a DMA for which adequate service reservoir is available shall be selected). 

2.    Estimate the valve controls for each sub-DMA from lower level (tail end) to higher level (towards reservoirs) such that controlling a lower valve will increase pressure at higher side. It should be seen that quantum of supply does not get increased. Proceed upwards with this approach and control each valve at starting of each DMA and sub-DMA. It is important to note that to do such type of valve operations a good communication system along with good number of manpower is required. The adjustment of valves can be done in phase wise manner in day to day basis such that there will be minimal disturbance to the end user. 

3.    As valve adjustment is started, increase the supply hours step by step may be done simultaneously.  The increase in supply hours shall be noted.  In this process of control we need a back-up reserve to feed the aspiring areas instantly.

4.    Simultaneously record the ESR/GSR level of the DMA so that the effect can be monitored on the level of ESR/GSR. 

5.    The trial and error adjustment in the valve control along with increase in supply hours shall be carried out until the ESR/GSR is not getting emptied / overflowing.  This requires an exhaustive effort with a team work along with participation from the community.  In the course of time the ultimate objective shall be to bring valve control adjustments to nil. 

6.    An awareness drive for the community shall accompany the transition period to avoid any panic due to change of service in the water supply. 

7.    After successful adjustment with regards to valve control and supply hours a continuous monitoring plan shall be devised and implemented.  Parameters such as ESR/GSR level, inflow and outflow from the reservoirs, water pressure at the consumer end, etc. should be continuously monitored. 

8.    Once 24x7 water supply is achieved in one DMA, based on this experience and the approach, other DMAs can be undertaken for transitioning to continuous 24x7 water supply. 

3.3 Expected time span for the change.

As emphasized above the efforts of converting intermittent water supply to 24x7 water supply is exhaustive and it takes considerable time along with team work.  Table 1 provides tentative timeframe for converting intermittent water supply to 24x7 water supply. 

Table 1 : Tentative Timeframe for 24x7 water supply

Sr. No.	Activity	Time	Cumulative time
1.	Collecting field information such as ESR operating levels, pumping hours, inlet/outlet flows, etc.	7 days	7 days
2.	Locating/identifying salient valves and opening for operations	4 days	11 days
3.	Valve control and observations four trials. Once the opening areas are fixed for valves, they can be replaced by master pieces (pipe in pipe), in a phased manner	3 days each (total 12 days)	23 days
4.	First change of supply from 5 hours to 8 hours, start meterization.	14 days	37 days
5.	Second change from 8 hours to 12 hours, complete 70 % meterization	30 days	67 days
6.	24 hours supply in storage and 12 hours supply, complete 100% meterization	13 days	80 days
7.	a. 24 hours of incoming and 24 hours of supply b.Checking the consumer wise LPCD and overall supply quantity to the DMA.	60 days	140 days
8.	Optimization of supply level and LPCD as a reaction to bills, indicating their satisfaction level	60 days	200 days

 

During the process it will be of help to keep a record of man power inputs and material inputs and get valued each day. At each mile-stone the cumulative financial inputs can be noted. Final cost inputs will be available for getting an insight regarding the time and expenditure required for the other areas to be covered. It is very likely that the process will be more streamlined in the areas to follow.

3.4 Proposed Automation

Apart from above steps it is essential to install sophisticated instrumentation and control system for easy operation of the system.  Some of the instrumentation systems are suggested below:

1.    Leakage detection system: This is required when the network is vast especially for municipal corporations. The automation provides hooking up of the local leakage analyzer's interactive mode to SCADA and as the leakage in a section starts, provides on line information of the section of distribution to ease the immediate rectification.

2.    Automatic ESR management system:  The principle is based on the inlet and outlet valves installed for each ESR where the valves have remote connectivity with SCADA. It maintains the optimum level of the ESR with minimum offset which is decided for equitable pressure in distribution. These valves operate 10% to 90% controllable range for efficient automation to control the water level.  These valves have additional feature of calculating the volumetric flow through time averaging on basis of valve opening.  Valves could be commanded through SCADA for timed opening and various logical combinations to ease the operation either in normal mode or in an emergency mode.

3.    AMR consumer meters.

4.    Portable Ultrasonic meters.

4.    Discussion

The above road map suggests that conversion from intermittent operation to 24x7 water continuous supply is a step-by-step process with a defined direction. It has a slow transition as it supports and identifies the resistance to change in the operational exercise and also in the consumer behavioral reactions. Slow process of pressure reduction mixed with increase in supply hours shall not have the reactions to resist for the change from the proactive residents in the area.  Instead there shall be a constant interaction with the consumers in different areas where change is occurring. 

24 x 7 supply is normally resisted for the fear for the increased billings. Meterization shall be associated with the transition. It will help and educate consumer to react positively to the increased billings. Being a slow process consumer need not feel the change in the bills for at least three billing cycles. Initially daily AMR meters can be read to understand the change by the operational staff and the consumers and required information based change can be monitored by both.

Hence, putting efforts on the level of service improvement shall also address the level of satisfaction of the consumer and lead to the success of the transitional change. It is important to note that initially system will be tested for the capacity to run at higher level of service and from operational side there should no hidden or open resistance to the transition, till consumer reacts positively to the increased bills and controls the consumption to the norms. It will take at least two billing cycles more. Operational staff shall have to bear with the change.

Finally, following changes will be observed for successful implementation of 24x7 water supply operation:

1.    ESR will not become empty, and not overflow.

2.    There are equitable pressures in the system actually observed. Valve operation will be minimized.

3.    Consumers at any point will get practically equal water quantity in a day.

5.    Household storages will be eliminated with the confidence building in the consumers.

6.    Any shut downs can be, planned shut downs.

7.    Billing efficiency will be improved.

8.    When the staff is consistently on watch in the transition period, unauthorized connections are identified.

9.    Working of meters will be improved.

10.  Seasonal changes in supply can be easily worked out.

11.  Consumer behavior will be correlated with operational system.

5.    Conclusions

The study shows that achieving 24x7 in old water supply schemes is challenging task.  In this study it has been emphasized that before undertaking transition of WSS to 24x7 water supply it is necessary to undertake reform works.  Reform works gives an opportunity to ULBs to better understand their WSSs technically and financially. Without knowing the present status of WSS it is difficult to develop a road map for conversion to 24x7 water supply. 

It is found that hydraulic modeling plays a critical role in development of road map for converting WSS from intermittent operation to 24x7 continuous mode.  Hydraulic modeling analysis help in developing rehabilitation plan for WSS with better utilization of existing water supply infrastructure.  The optimal investment can be suggested with hydraulic modeling.  Hydraulically isolated DMAs can be formulated for better service delivery and monitoring of WSS. 

References:

Sashikumar, N., Mohankumar, M.S. and Sridharan, K. (2003)  Modeling an Intermittent Water Supply.  World Water & Environmental Resources Congress 2003

Mays (2004) Water Distribution Systems Handbook McGraw-Hill, USA

High Powered Expert Committee (HPEC) Report (2011) for Estimating the Investment Requirements for Urban Infrastructure Services. 

---

[*] Corresponding Author: Dr. Pradip Kalbar (Email: Pradip_kalbar@synergyeesolutions.com, pradipkalbar@gmail.com)

[†] Litres per Capita per Day