Cause and response to green algae

‘Green algae’ is a phenomenon that the color of water changes to green due to a mass propagation of ‘algae’ such as green algae and blue-green algae in river and lake.
‘Algae’ are phytoplankton which eats nutritive salts such as nitrogen and phosphorus and photosynthesizes with light and are food to zooplankton and do the same things as land plants do in water ecosystem.
Nevertheless, harmful algal blooms bloom, a phenomenon of mass and rapid algae bloom occurring when water temperature rises due to excessive nutritive salts created by the inflow of various pollutants into river or lake, threatens water ecosystem and causes various other problems including bad smell.

Features and cases of harmful algal blooms bloom

Harmful algal blooms bloom generally occurs from early summer to autumn, during the seasons when water temperature is high, and features of harmful algal blooms bloom by major algae are as follows.

Classification	Propagation period	Color of water	Problems
Green algae	Spring to autumn	Dark green	Smell of grass and moss, etc.
Blue-green algae	Early summer to autumn	Navy or dark green	Toxin, smell of mold, etc.

(reference) Diatom : This kind of algae propagate from late autumn to spring when water temperature is low and its mass propagation changes the color of river to brown and creates fishy smell.

A Water quality warning that requires attention and caution was issued in 2013 in  Nakdong River, Geum River, and Yungsan River due to lack of rainfall and intense heat and green algae also occurred frequently in the past due to the inflow of a great number of nutriments by rainfall after rainy season in summer and temperature rise.

* Water quality warning : A system that forecasts the degree of algal occurrence in order to prepare against problems from green algae in river in advance, like a weather forecast (Ministry of Environment, twice a week normally)
- Issuing water quality warning depending on chlorophyll-a concentration and number of blue-green algae cells [attention-caution-warning-alert] (chlorophyll-a -a : a chlorophyl element contained in every algae)

Cause and prevention of green algae

• harmful algal blooms bloom occurs with a complex action of water temperature, sunshine, nutrient salts, flow velocity, and other such elements and some claims that the cause of algal bloom is flow velocity lowered by the construction of dam and barrage.
• However, dam and barrage are essential to stable annual water supply, minimization of flood damage, and balanced development of national land, responding to global climate change including climate characteristics such as concentrated rainfall by season and region and localized heavy rain in Korea. Furthermore, algal bloom does not occur with gentle flow velocity if there is no pollutant in river.
• Therefore, fundamental improvement measure to algal bloom is to reduce the amount of nutrient salts which are food to algae and, to fulfill such task, we need to reduce the inflow of pollution source into river systematically by stages through maintenance of sewage, reinforcement of management of livestock wastewater around river, and enlargement of treatment facilities.

Direction of the company’s reaction

To develop preventive activities to algal issues aggressively, K-Water performs daily water quality warning system by itself from February 2014 and makes efforts to investigate the cause of algal bloom and to expand its role in eliminating pollution sources through discussion with related organizations such as Ministry of Land, Infrastructure and Transport and Ministry of Environment

※ The scope of water quality management by K-Water at present is restricted to 1km of upstream and downstream of dam reservoir and barrage

We aim to respond to the issues aggressively, rather than keeping old passive action performed only when algal bloom occurred, by discharging pondage of dam and barrage in advance anticipatorily depending on the results of monitoring of symptoms of algal bloom. We also plan to reinforce countermeasures in various fields by seeking solution through great debate with the nation, government, and academy, establishing policies on river management by water system, constructing integrated governance for quality and quantity of water, researching and developing new techniques for removing algae, and performing promotional activities.