Design of a Water Environment Monitoring System Based on Wireless Sensor Networks

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Introduction
The water environment, consisting of the surface water environment and underground water
environment, can be differentiated to water bodies like rivers, lakes, reservoirs, oceans, swamps,
glaciers, springs, and shallow or deep underground waters. The water environment, as well as other
environmental elements like soil, organism and atmosphere, etc, constitute an organic complex. Once a
change or damage to the water environment is observed in this complex, changes to other
environmental elements inevitably occurs [1]. Due to the speed of China’s economic development, we
can also see the resulting speeding-up of contamination and damage to the water environment. In this
sense, water environment monitoring, as one of the major methods for water resource management and
water contamination control, is found to be more and more indispensable.
At present there are mainly four methods for monitoring water environments, each of which has its
advantages and disadvantages:
1) Artificial sampling with portable water quality detecting devices and subsequent lab
analysis. This method applies only to samplings on cross-sections of river and lakes with a
sampling frequency ranging from several times a day to monthly.
2) Automatic and continuous monitoring of water environment parameters by an automatic
monitoring system consisting of monitors & control centers, as well as several monitoring
sub-stations. Data can be remotely and automatically transferred. Each station provides its
real-time water environment parameters. These systems can be costly and have a great
influence on the surrounding ecological environment.
3) Water environment monitoring with remote sensing technology, namely detecting the
spectrum specifics of an electromagnetic wave (radiation, reflection and scattering) in a
non-contacting method with respect to the water body. After the processing of the
information from the collection of illustrative spectra, its physics and chemical
characteristics are to be identified. However this method can only provide a low accuracy,
and it is also hard to perform real-time monitoring.

Design of Monitoring System
The proposed water environment monitoring system based on a WSN is illustrated in Figure 1. It
can be divided into three parts: data monitoring nodes, data base station and remote monitoring center
for the water area being detected [9]. A great number of data monitoring nodes, distributed in water
area to be detected, dynamically constitute a monitoring network, in which each node can only collect
parameters such as pH, amount of dissolved oxygen, electrical conductivity rate and temperature, but
also is capable of operating linearization and temperature compensation, data packaging, collected
parameter memorizing and routing to a data base station; the data from the monitoring nodes is
transferred to a remote monitoring center by the base station via a GPRS network; the monitoring
center analyzes and processes the water quality parameters, gives an alarm for emergencies like water
contamination, in addition any sudden changes in water quality, and provides support for decisionmaking
in prevention and remediation of water contamination; the end-user can also realize an allweather
detection on the target water area via the Internet. The whole water environment monitoring
system presents useful characteristics as large network capacity, flexible disposition, low power
consumption, low cost, and minor influence on the natural environment.



Design of Hardware and Software for the Data Monitoring Nodes
Monitoring nodes, as the basic unit of the monitoring area of the water environment, are the basic
units to realize the monitoring function. At present, the major functions of the monitoring nodes are:
1) Collecting the temperature and pH data of the water area to be monitored. The pH and
temperature sensors installed on the monitoring nodes can meet the above needs and realize
the linearization and temperature compensation for the data collected.
2) Setting up a wireless network based on the ZigBee protocol. A great number of monitoring
nodes and base station a dynamically assembled into a wireless network based on the
ZigBee protocol, via which the pH and temperature data, etc., shall be routed to a base station.