A Review on Comparison of Different Water Leak Detection Techniques Suitable for Indian Scenario

Effective management of water distribution is necessary for any country worldwide by reducing water losses during different utility operations. Also in India, water loss is the biggest challenge for the municipalities and local bodies of various states. Different researchers had tried to give attention to this issue and its effective solution through different techniques. In this research papera summarization of different methods used to identify and locate the leakage with its merits and demerits was given. A review of different leak detection techniques from randomly selected research papers in the form of a comparison table considering suitability, methodology, outcomes, and limitations by different researchers suitable for the Indian scenario was also presented.In the end, an effort was made to emphasize the selection of the appropriate method for leak detection and localization of leakage suitable for Indian conditions.


Introduction
We know water is one of the important gifts given to mankind from nature. Water is the source of happiness, wealth, and prosperity in the daily life of mankind. There are limited available resources of water in the different parts of the world, India is one of them and a decrease in the quantity of it spreads scarcity to the users. 1 Developing countries like India, China, countries of Africa, and Bangladesh have expected more water scarcity as compared to other countries with the consideration of population growth and migration towards major cities of countries. 2 To fulfill this,every major city of India expands its distribution network concerning an increase in water supply demand due to the growth of population as well as the development of the new area in different directions of the cities. In India, around 19% of water is consumed by industries, while around 70% of water is utilized by farming or agriculture. 2 This will result in the need for effective distribution of water throughout the whole country. The demand of water is expected to increase in the future in India and the projected demand for water exceeds 50% by 2030 and around 600 million peoples of India face water shortage resulting in 2,00,000 loss of life every year from inadequate access to drinking water. 3 So, the gap between the demand of users to the sources of water supply increasing rapidly in India and in this situation, water conversation, and reduction of water leakage in distribution pipe networks need to be importantly studied. 4 India is one of the developing country and the loss of water in a domestic sector with consideration of leakage is nearly 30% to 40% of the total flow during distribution of water through pipe network. 5 Losses in the distribution of water have a great economic impact on the Gross Domestic Products (GDP) of the country. So, an effective methodology or solution for the better management of the water distribution of the network by minimizing losses will be a great relief to a nation like India, which faces the problems of losses of water from a large network of pipesand difficulties to maintain and operate the water distribution network efficiently withoutany loss of water. In India, the design of pipelines for distribution is based on Continuous Water Supply (CWS) guidelines, and the operational work for the distribution of water is done as per the Intermittent Water Supply (IWS). 6 The main cause of water losses is leakage developed in different components such as distribution pipes, transmission pipes, pipe connections, pipe joints, valves, hydrants as well as the whole distribution system during water distribution operations. The estimated loss due to leakage is considered 70% of total loss in water distribution networks, especially in underground pipelines. 7 Leakage is mainly due to pipe material defects, pipe aging, corrosion, design fault in installation, traffic movement above the pipeline,etc. 8 The basic economic loss due to leakage is the raw water treatment cost and its transportation costincluding erosion of bedding under pipe, pipe breakage, and the foundations of buildings and roads nearby pipes. Therefore, designing a cost-effective solution to identify and locate the leakage is quite needful for all the smart cities of India in the upcoming days for effective management of the distribution of water through a network of pipes. Here in this research paper, an effort was carried outto draw attention to the suitability and comparison of different leak detection techniques suitable forthe Indian scenario. In section 2, the classification, instrumentations, merits, and demerits of different leak detection techniques were presented. While in section 3, a review of different research in the form ofa comparison table with review methodology was given. At the end of a research paper, a discussion based on the literature studied was presented with a conclusion.

Different Leak Detection Methods
There are many different methods adopted by researchers to detect leakage in the water distribution pipe network are Underground Wireless Sensor Network (U.W.S.N.), intelligent sensing and use of Information and Communication Technology (ICT), acoustic detection with noise logger and leak noise correlator, use of hypothesis and algorithm, use of thermal image with Infrared (IR) high-resolution camera, use of Ground Penetrating Radar (GPR), geophysical technique, hydraulic modeling, fiber optic monitoring, tracer gas, multi-model systems and many more. Generally, all smart cities of the developed and developing country of the world have an underground piping network for the distribution of freshly treated water among the city to maintain the beautification the city. So, it is very difficult to find the position of leakage as well as do effective management in the distribution of water without making any losses. If any method is available to find the approximate location of leakage in the pipe network, that will be a great relief to the local municipalities bodies to do repair work in time as well as save the quantity of freshly treated water which is ultimately wasted due to leakage. In this review paper, different methods for the effective management of loss of water are listed and the merits and demerits of each technique are given in section 2. While in section 3, the summary of the research work from randomly selected research papers was presented. At the end, discussion based on the review papers with the concluding part for the suitability or selection of proper technique of leak identification was given for a developing country like India.

Static & Dynamic Method of Leak Detection
In a static method ofleak detection, there is a use of different data collectors and different sensors that are placed within the water distribution network to collect different flow parameters. From the analysis of this data, there is a prediction of leakage from any remote place. These systems are said to static leak detection because all the instrumentation is static and on the predefined location of the network. While in dynamic method of leak detection, we have to depend on the dynamic leak devices that can be moved throughout the entire possible leakage zone. Movement of such devices depend on any previous data of leakage. The main difference between static and dynamic leak detection systems is that in static method of leak detection, it is based on analysis of data and leakage identified immediately with some accuracy. While in dynamic method of leak detection, we have to rely on the information of leak possibilities or past data of leakage. Also, the dynamic method give approximation location of leakage as well as it is time-consuming as compared to static method of leak detection. 9

Acoustic & Non-Acoustic Leak Detection
In the acoustic leak detection system, measures the sound generated by leakage with the use of different acoustic devices such as listing rods, ground microphones, noise loggers, aqua phones, geophones, etc. In this method, heavy instrumentation is required and placement of such devices in the pipeline is another issue. Also, the small leakage in the pipe, which generates very little noise has not been detected effectively. Localization of the leak is also difficult with the use of this type of devices, which are placed far from the actual position of leakage. While, in the non-acoustic method there is a use of different sensors to monitor flow, pressure, temperature, vibration, etc., to collect the data, and then after different modelling and algorithms techniques have been used to analyze such data. As there is a collection of different flow parameters with the help of sensors in this method, small or minor leakage is also identified and localization of leakage can also be done by the analysis of such data.

Traditional & Modern Leak Detection
Traditional methods used for decades to find leakage such as physical monitoring of pipes, use of robots in the pipeline, acoustic methods, use of thermal images, etc. Heavy instrumentation is required in these methods and very difficult to use in the case of underground pipe networks. While in modern techniques, there is a use of different types of sensors to collect data with the platform of ICT or Internet of Thing (IoT), and analysis of the collected data has been done using different algorithms and modeling techniques. In modern techniques, leakage can be identified and localized from any remote place while with the use of traditional methods there may be physical visits made through a complex pipe network before or after.Use of traditional methods required more man power as compared to modern technique.  9 of material used for the inspection is going on. pipe, and the size • Depend upon pipeline of the pipe.
bedding and surrounding • Does not require condition a skilled person • Instrumentation is costly.

Comparison of Different Leak Detection Methods
Many methods are available to detect leakage in pipe networks but practically before implementation of any method in the real scenario the laboratory experiments, analysis of data, and validation of the output must be carried out to check the effectiveness of the method in particular conditions. With the above consideration, the advantages and disadvantages of different methods with the instrumentation are summarized below in table 1 for the comparison and appropriate choice of leak identification method in the related case.

Literature review
The literature review presented here was based on the research papers published in peer-reviewed journal in the field of effective management of water losses, observation or monitoring of different flow parameters during distribution of water in pipe network, leakage detection in the water distribution network, and some cases studies of leakage identification. Different search strings were used to search research articles like "Losses in the water distribution network in India","Leakage identification in the distribution network in Indian condition" and "Water scarcity in India". Numbers of papers were found addressing the losses of water and leakage detection methods inthe Indian scenario as well as in other developing countriesas the problem was an older one. In this review paper, recent research papers published from the year 2014 to 2021 were considered. A detailed reading of the abstract and conclusion was done to classify and compare the articles based on analysis, method, and instrumentation used, Suitability in a particular condition, outcomes, and limitation of the research work. A detailed comparison of the above-stated points of the most recent research work randomly selected from the collected research papers was presentedhere in table 2. The limitations of the research work also presented to select the appropriate methods among the available methods in particular conditions. India has a wide range of variations in the distribution network of pipes based on topographical conditions, geographical conditions, the layout of the pipenetwork, different water supply systems, water source location, water demand in different sectors, and pipe size. So, the choice of a leakage detection system may be different in different conditions. A detailed discussion on this was given after this section for better implementation of a suitable method of leakage detection to minimize the losses of water.

Discussion
The Government of India (GOI) launched the mission 'Smart Cities in India' in 2015 for 100 cities within the country. To become a smart city GOI decided on many parameters, adequate water supply is one of them. So, there is a great chance to implement or introduce any techniques which result in effective management of loss of water during distribution through a complex and huge piping network. As found from the review of research papers there are many methods to identify the leakage and localize the leakage to reduce losses resulting in better management of water distribution. Water leakage is found using acoustic devices in developed countries based on vibration or sounds generated by the pressurized pipe, While in developing countries major leaks are found only when they appear on the surface of roads in case of underground pipe network which is resulting in a considerable amount of wastage of water. 5 From the review of research papers, it was found that in earlier days acoustic method is mostly used in developed countries for leak detection but nowadays the use of IoT, wireless sensors, machine algorithms, and neural network techniques have increased as compared to the traditional method.
As there are many existing leak detection techniques the selection of a proper leakage identification method will depend on many parameters such as flow parameters, pipe aging, the distribution network of pipes, pipe material, full supply or intermittent supply, size of pipe, underground network, surface network, water source, fund allocation, awareness of local bodies, etc. It is very difficult to select and rely on any method because effectiveness in individual cases may be different from case to case. Different research work is carried out by many researchers in this direction and as a result, the implementation of any leakage detection method depends on many parameters as each method has its own merits and demerits. The comparison of different research work carried out recently shows there is different instrumentation is needed for each method. In India, most of the cities supply the water with IWS systems that means less than 24 hours per day resulting in distribution with pressure. So, major parts of India have underground pressurized pipe networks for the distribution of drinking water. In this situation, the leakage detection method which dependsupon the flow parameters that are flow and pressure give better result as compared to the methods which are used for the CWS system. Also, we have to see the feasibility of the implementation of different instrumentation for different methods in the already developed underground water distribution network of the city without disturbing the supply of water.

Conclusion
From the study and comparison of different methods and looking at the fact that in the Indian scenario most of the cities have IWS systems with pressurized pipes in underground water distribution networks, the Wireless Sensor Network(WSN) technique is more suitable with the use of IoT in most of the cases for identification of leakage. WSN technique is the latest and most modern technology to detect leakage in the pipelines as compared to the traditional method and it has many advantages which overcome the limitations of other methods. To locate the leakage, we have to use mathematical modeling or machine learning algorithms or use of any artificial intelligence technique from the collected data by wireless sensors. The advantage of using a wireless sensor network is its suitability in any situation, fewer instrumentations require, the system once established can be used for a long time, and collection of data from sensors can be done from any remote place. This system could be easily implemented in the already established water distribution network. However, more research work should be carried out to implement WSN technique effectively in terms of an optimum number of sensors, cost of the sensor, the accuracy of the sensor, placement of the sensor, method for analysis of data received by sensors, effectiveness in a real scenario, and validation of simulation of the model.

Acknowledgment
I acknowledge my Parents, wife Ankita and My lovely daughters Nemi and Priya for the support and inspiration.

Funding
The author(s) received no financial support for the research, authorship, and/or publication of this article.