“The Water level Condition of Nam Ngum 1 reservoir”

Since the notification of EDL-Generation Public Company to Permanent Secretary of Vientiane Capital and Vientiane province on the 9^th August 2018 that Nam Ngum -1 Hydro Power had had released water through its spillway at 9:00 AM of the 12^th August 2018 in Keo Oudom district, Vientiane province. All four channels of spillway gate were opened at 40 cm high, allowing 148 (one hundred forty-eight) cubic meters of water per second flow to downstream of Nam Ngum river. It’s anticipated that water level in downstream could increase between 5 cm to 10 cm after the opening the spillway. At the same time, the management team of Nam Ngum 1 HPP had assigned a specialist team to observe the growth of the water level in each specific area to inspect and report the progression.

Therefore during 10 days of the opening of the spillway, it was opened and reduced the high due to the actual situation. So that EDL-Gen could update the water level condition of Nam Ngum 1 HPP on 22^nd August 2018 at 8:00 AM that:

1. Reservoir water level and Tail water level

• Reservoir water level is at 211.58 masl, Reservoir water Volume = 6,873,738,200 (six billion eight hundred seventy-three million seven hundred thirty-eight thousand and two hundred) m³compared to 8:00AM (21/08/2018) decreased 2 cm.
• Tail water level is at 170.6 masl compared to 8:00AM (21/08/2018) decreased 1 cm.

At 22:00 of the 19^th August 2018, the high of the opened spillway gate was reduced from 3.0 meters to 2.7 meters, Spillways discharge = 998.3 m³/second.

2. Stream gauge data along NNG Downstream River compared to 8:00PM of the 21^st August 2018:

• Water level at Pak ka ngoung gauge is 10.02 meters at 8:00AM has increased 02 centimeters.
• Water level at Vernkham gauge is at 11.66 meters at 8:00AM, it seems that the water level increased 15 centimeters.
• Water level at Hin Herb gauge is 5.40 meters at 8:00AM has decreased 64 centimeters.
• Water level at Ban Hatsuan gauge at 8:00AM has increased 15
• Water level at Tanpiow gauge at 8:00AM has increased 10
• Water level at Ban Choum gauge at 8:00AM has increased 05 centimeters.
• Water level at Ban Cheng gauge at 8:00AM has decreased 15 centimeters.
• Water level at Boungphao gauge at 8:00AM has decreased 17 centimeters.

The opening of the spillway gates is strictly performed following the safety standards and the EDL-Gen Water Release Management Procedure for Nam Ngum 1 HPP to ensure that the water release remains safe. Water discharge is a standard practiced in such case the water level in the dam reservoir increases due to heavy rainfalls and since it is rainy season more rains and storms are forecast during this August and September. To minimize the impacts on the villages located along Nam Ngum River, the reservoir will act as buffer to receive the large incoming flows volume and then release the water smoothly through the spillways.

For daily information of the water level situation of EDL-Gen’s HPPs, please check at www.edlgen.com.la

Photo and Report news by: Public Relation Division, EDL-Generation Public Company.