Reduction in Poulaphouca Lake Levels

Poulaphouca Reservoir viewed from above Valleymount. © Eugene Brennan

The water level in Poulaphouca lake has dropped from yesterday's 186.64 m to 186.52 m a drop of 12 cm. It may seem small, but it corresponds to a discharge of 2.7 million cubic metres (m³) of water for the 22.6 square kilometre lake. This reduction in volume of the lake is simply due to the difference between "water in" minus "water out". The River Liffey and Kings River are feeding water into the lake, and water is discharged through the Poulaphouca dam into the Golden Falls Compensatory lake. In a previous article, we discovered the reason why there's a lake between the two dams. Some of the drop in level is accounted for by water purified into drinking water by the Ballymore Eustace Water Treatment Plant. According to the EPA, the BWTP produces 340 million litres of drinking water a day. That's equivalent to 340,000 cubic metres. So most of the reduction in water volume in the lake is accounted for by Poulaphouca discharges. Liffey releases through the Golden Falls dam today are forecast to be 45 cubic metres per second, (m³/s) all day. If that rate of discharge is sustained for the day, (the ESB say "flows are estimates") it corresponds to 3.9 million m³ of water discharge versus the 2.7 million m³ reduction in volume of the Poulaphouca lake. So at the moment, the total discharge from the Golden Falls lake is greater than the rate at which the Poulaphouca lake is discharging into it, making room for high flows on rivers and lakes feeding the lakes in the coming days.

Water level stats courtesy ESB hydrometrics. 

 

Water level stats, courtesy ESB hydrometrics. 

Related Reading

• Press Release From the ESB About Potential Releases From the Poulaphouca Reservoir (this explains the setup at Golden Falls and the buffering of flow)
• What Volume Does a 1 m Change in Water Level Represent in the Golden Falls Lake? 
•  Golden Falls Headrace Level Up a Metre, Flywheels, Capacitors and Air Compressor Tanks
•  Let's Do Some Calculations: How Much Water?
•  High Volume Releases at Golden Falls Dam
•  Golden Falls Generator Assembly
•  Erosion of the River Bank in Kilcullen
•  Ballymore 5 km Loop