Water Quality Monitors Protect Rivers During Drought

Graham Mellor for YSI Hydrodata

Due to the drought in the southeast of England during 2005 and 2006, the Environment Agency has allowed increased water abstraction from certain rivers in order to protect reservoir levels. However, reduced flow can cause deterioration in a river’s water quality. In order to maintain acceptable levels, the Environment Agency imposes water quality conditions within Drought Permits.

It is under the conditions of these Drought Permits that Atkins Limited has deployed water quality monitoring and telemetry systems from YSI to ensure the protection of rivers during recent drought conditions.

Saving a reservoir

Sutton and East Surrey Water was granted a Drought Permit in fall 2006, allowing the company to begin abstracting water earlier than normally would be permitted in order to replenish Bough Beech Reservoir.

Bough Beech Reservoir lies to the north of the village of Bough Beech near Edenbridge. Built in 1968, the reservoir was designed to meet the water storage needs of the then East Surrey Water Co. The reservoir only has a small catchment with five small inflows. Most of the water is usually pumped in during winter months from the River Eden near Chiddingstone.

Flow measurement is carried out at a gauging station on the Eden to ensure that abstraction does not cause the river to drop below acceptable levels.

Under the terms of the Drought Permit, Atkins Water and Environment monitors water quality at a site downstream of the Eden abstraction. The monitor is a YSI multiparameter sonde fitted with sensors for pH, dissolved oxygen, temperature and conductivity. The sonde is suspended in the water by a chain connected to a stake on the riverbank.

The monitor is fitted with a new YSI telemetry system (EcoNet) that collects data to an internal datalogger and transmits via GPRS to a web-based server in the U.S. Therefore, authorized users can access data from anywhere with Internet access. This technology allows the facility to configure the unit to issue email alarms and to increase the frequency of sampling during alarm conditions.

Close monitoring aids abstraction

Atkins Water and Environment has been contracted to provide the monitoring service during the additional early abstraction period (September and October). Under the Drought Permit, dissolved oxygen levels downstream of the abstraction should not fall below 50% saturation. According to Tom Wood, who is responsible for the instrumentation at Atkins, the YSI Econet monitoring system has allowed the company to closely monitor the water quality over the web server from its office in Epsom.

During early September, it was not possible to commence abstraction because the river levels were below the minimum required by the Environment Agency. These low flows resulted in low oxygen levels, which also prohibited the water company from starting abstraction. Rainfall during the second week in September increased flows, bringing the water quality within the requirements of the Drought Permit.

The YSI Econet telemetry system has enabled Atkins to advise Sutton and East Surrey Water exactly when water quality is acceptable so that the company can begin abstracting as soon as river levels are sufficient.

Atkins deploys YSI water quality monitoring sondes routinely in a number of different applications. For example, they were used to provide data during the River Medway scheme Winter 2006 Drought Permit. Atkins also employs the sondes under a framework agreement with Southern Water to provide long-term water quality monitoring for the development of water resource management strategies in the area.

"We use YSI multiparameter sondes because they are able to provide reliable long-term data,” Wood said. “The facility to view and collect data over the Internet is an exciting development—it means that we can now access the latest data any time from anywhere."