Researchers from IISc have made a prototype of a monitoring system that can help identify water losses and raise alarms.
According to a UNICEF survey in 2013, India has only 4% of the fresh water resources of the world, for 16% of the world population. Measurements of per capita water availability indicate that India is currently water stressed; future projections indicate that India may have water scarcity by year 2050. In this scenario, leakages in the water distribution system can have a huge impact on water availability.
A lot of resources and money is spent in purifying and cleaning naturally available water to make it potable. Loss of purified water is a waste of these resources and a financial loss to the water distribution authorities. In addition, leakage points tend to deteriorate the pipelines and also pose a risk of exposing water to bacteria and other impurities. Thus it is extremely important to identify water losses so that corrective action can be taken. “It has been observed that a large amount of water loss happens close to the source of purified water, even before the distribution network” says study author Vignesh Kudva.
The team has made a prototype to measure inflow and outflow of water for a medium sized campus. The testbed was the water distribution system over a part of the IISc campus. Water supplied from water distribution authority is stored in ground level reservoirs and overhead tanks and is further distributed to the rest of the campus. Inflow of water can be measured at the point of water entry inside the campus. However, measuring outflow at all the output pipes can be challenging.
“Many pipeline systems are underground. It is a tedious and costly affair to identify the correct places, dig and install sensors at the correct locations”, Vignesh explains. The alternative to this is to install flow measurement sensors at the input and then measure water volume in the water reservoirs. The volume of water inside the reservoir would give the accumulated difference between inflow and outflow of water. We can then calculate outflow.
Water volume measurement can be done by pressure gauges immersed in the water or by non immersion type water level measurement. The researchers have chosen the non-immersion method, as it eliminates possible risks of water contamination and is easier to maintain. The method works by fitting an ultrasound transmitter and receiver set at the lid of the water reservoir. The volume of water can be calculated by measuring the distance of water level from the lid.
Inflow measurement sensors and water level sensors were fitted with wireless transmitters. The sensors transmit the measured parameters to a central gateway which then transmits it to a database server over the internet. Researchers had an option of installing a GSM module with the sensors so that cellular network can be used for communication. But this scheme may have problems in later deployment as some reservoirs may be placed in remote areas where cellular signal may not be present. So they chose to use sub giga Hz communication.
Researchers used EPANET, the US Environmental Protection Agency’s modelling software for modelling of water supply distribution system, to model their testbed water distribution system. Then they used this model to analyse the flow and water volume data. The reservoir water volume graph shows a typical pattern according to inflow and usage of water. Any anomaly in this pattern could be used to raise an alarm. Co-author Vignesh informed, “For example, during the research period, we realised that the water volume inside a certain reservoir had gone down to zero in a very short interval. The programmed alarm system sent a warning signal. Investigations pointed to a tap that was accidently kept open”.
The advantage of this system is that it could be constructed from off the shelf, not very expensive components. The design of the sensor module fitted on the lid of the water reservoir can be critical as the angle of the lid could be random and not necessarily parallel to the water level. The sensors consume very little power and the estimated battery life is about 2 years.
This system is an important step towards real time monitoring of larger water distribution systems. There could be challenges. A sound knowledge of the water distribution system is necessary to place the sensors at appropriate points. Pipes being underground may make it difficult to choose monitoring locations and install sensors. Also, the communication range needed for the wireless transmission system may be large. This could reduce the battery life. The sensors also need to be made tamper proof to avoid accidental tampering or intentional theft. Kudva says “The best way to do this is to install monitoring system components at the time new installations are made”.
Vignesh Kudva and Prashanth Nayak are graduate students at Department of Electronic Systems Engineering, Indian Institute of Science. Alok Rawat is graduate student in Center for Product Design and Manufacturing, IISc. Anjana G. R. and Sheetal Kumar K. R. are graduate students at Civil Engineering Department, IISc. Bharadwaj Amrutur is faculty at Department of Electronic Systems Engineering, IISc and M.S. Mohan Kumar is a Professor at Civil Engineering Department, IISc.
Contact: Vignesh Kuvda firstname.lastname@example.org
The paper appeared in the journal IEEE Xplore (link). It was presented at the 28th International Conference on VLSI Design (http://vlsidesignconference.org). The PDF is available online at http://chips.ece.iisc.ernet.in/images/6/69/Vignesh_Water_Sensor_VLSI_2015.pdf