Aabha Sargaonkar

Model study for rehabilitation planning of water supply network

Abstract Inefficient delivery and inadequate coverage of water supply and sanitation services are major concerns for public health in the urban regions of developing countries. The contamination of the treated water within distribution system leads to frequent outbreaks of waterborne diseases. This demands a proactive approach that is based on risk assessment and a management methodology to ensure water safety. In this context, the paper presents a model study undertaken for the water supply network of a pilot area in Hyderabad city, India. The risk assessment methodology uses geospatial databases of the water supply network, sewer network, open drains, groundwater table, pressure in pipes, and soil data with a number of system-specific attributes. Fuzzy multi-criteria evaluation approach with qualitative and quantitative domain knowledge is employed in pipe condition assessment model. The physical parameters viz. pipe age, material, diameter; operational parameters viz. intermittency, number of breaks and bursts, and leakage in the system; and environmental parameters viz. workmanship, bedding condition, and traffic determine the vulnerability of pipes to contaminant intrusion. The zones of contamination formed in the soil near open drains and sewer crossings (i.e., hazards) are delineated using a contaminant ingress model. The risk of contaminant intrusion is assessed as a function of vulnerability and hazard. The results indicate that roughly 3% of pipes in the network are in Bad condition and require rehabilitation on a priority basis; about 46% of pipes are in Medium condition. The study describes a techno-economically feasible approach to assist water managers and policy makers in delivering safe drinking water.

Risk Based Analysis for Contamination Event Selection and Optimal Sensor Placement for Intermittent Water Distribution Network Security

Water distribution networks are vulnerable to various contamination events that may be accidental or purposeful. Sensors are required for online monitoring of water quality to safeguard human health. Since sensors are costly, their numbers must be limited that makes sensor locations crucial in the water monitoring system. This paper aims at location of sensors in intermittent water distribution system which are more prone to accidental contamination due to contaminants ingress into the pipe lines because of low pressures during non supply hours. Considering deployment of limited number of sensors, the novelty of the paper is to propose a methodology for selection of contamination events with associated risk to be used in design of sensor network. Integrated risk assessment model is used to identify risk prone areas that may lead to possible contamination events. A Genetic Algorithm based methodology is suggested for optimal location of water quality sensors to maximize the detection likelihood of the contamination events within the acceptable time from the risk prone areas to improve network security. A comparison of sensor network design is made by considering contamination events occurring with: (i) equal probability at all the nodes; (ii) equal probability at risk prone nodes; and (iii) probability of occurrences based on quantified risk, to show that identification of risk prone areas and selection of contamination events results in reduction of computational work and more sensible placement of sensors.

Implementation of water safety plan for a large-piped water supply system

A water safety plan for the city of Nagpur was developed by the National Environmental Engineering Research Institute (NEERI) and Nagpur Municipal Corporation (NMC). Possible hazards were identified through field visits. Based on this, an improvement plan was drawn up to suggest corrective actions and a time frame for implementation. The findings of this study are being used to modify or repair components of the water supply system and upgrade management procedures. This paper highlights the lessons learnt during implementation of the WSP and the key challenges faced.

Dispersion study for two‐dimensional modelling

Simulation of water quality variation in a particular river stretch or at a particular location with time requires mathematical modelling based on advection and dispersion phenomenon. In this context, estimation of an appropriate dispersion coefficient, which is a function of characteristics of a water body, is very essential and forms an important step in mathematical modelling. The tracer study conducted in this context on the river Ganga to estimate the dispersion coefficient is described in this paper with an analysis of data based on a stream‐tube approach. For the wide river Ganga, with a velocity in the range 0.3–0.5 m/s, the estimated transverse dispersion coefficient is 1.33 m2/s.

Quantitative assessment of annual runoff in sub‐catchments using GIS: a case study of the Tapi River Basin, India

The Tapi is a major interstate, westerly flowing river with 14 tributaries, of which the left bank tributaries support large settlements in Maharashtra State. It has been identified as one of the water scarce basins of India. There are many dams and barrages in the basin to store and divert water for agricultural and industrial purposes. This results in low flow and deterioration of water quality in the region particularly in non‐monsoon months. This paper presents the details of a GIS‐based rainfall‐runoff modelling study carried out to assess the runoff flow in the sub‐catchments and at the outlet of the Tapi Basin. Using mean monthly rainfall data at seven gauging stations in the basin, and land use and soil characteristics as reported by the Central Pollution Control Board (CPCB), the annual runoff flow at the watershed outlet was estimated to be 18,814 MCM. A comparison of runoff generated in the sub‐catchments and the observed runoff at Central Water Commission (CWC) monitoring stations is presented. Results of the simulation indicate that the reduced river flows caused by the number of dams/reservoirs constructed upstream are useful as a guideline for the development of environmental flow regulations for rivers and streams in the Tapi Basin.