Measure for the quality improvement in basin

Hiroyuki NAKAJIMA Chief in management section, Kizugawa dam Integrated Operation & Management Office, Japan Water Agency

1. Introduction Japan Water agency which was founded in 1963 for the purpose of promoting the development of has been established and started its activities as one of Incorporated Administrative Agencies since October 2003. Tasks of JWA are to construct, reconstruct, manage and operate water resource facilities such as , canals, barrages and other facilities for control and water uses. JWA is now managing and operating 51 facilities completed in 54 projects, and implementing another 13 construction projects in the major seven systems designated for water resources development (Tone, Ara, Toyo, Kiso, Yodo, Yoshino and Chikugo River Systems). Dams have been often constructed in location with human habitation in upstream areas due to limited area, and it is not rarely the case that small towns are spread over underneath those dams. In this context, there are so many dams whose nutrient concentration of inflow water is considerably high, and water utilization damages are increasing due to phenomenon of , causing to direct public concern toward the problem of in dam reservoirs. Eutrophication is causing serious problems in dam reservoirs managed by JWA and a part of our reservoirs are troubled by blue-green algae and others caused by eutrophication in every summer season. The troubles include deterioration of landscape, deterioration of water quality due to foul smell and taste as as interference of plants. In this paper, we describe the outline of managing improvement facilities and their effects in our reservoirs.

2. The situation of eutrophication in JWA dam reservoirs The degree of eutrophication in reservoirs is classified into three trophic levels: oligotrophy, mesotrophy and eutrophy. Mesotrophic and eutrophic

-1- reservoirs with abundant nutrient salts are likely to experience excessive algae growth. A percentage of the changes in trophic conditions in JWA dam reservoirs, as reflected by the changes in the number of facilities in three different trophic levels(oligotrophy, mesotrophy, and eutrophy) in termd of total phosphorous and chlorophyll-a is slight decreasing during a decade(from 1996 to 2005). According to the data which were gathered from 27 reservoirs in JWA for the appearance condition of blue-green algae during this term, The figure of the number of facilities by month shows that blue-green algae increase from June to November and maximize in August and September. Freshwater red increase through almost a year, and in particular, increase from April to June before blue-green algae is superior. The figure of change of the number of facilities by year shows that the number of facilities where blue-green algae outbreak has increased until 2003, however it is decreasing after then. The number of facilities where had freshwater red tide outbreak had a trend of increase until 2004.

3. Water quality improvement facilities installed and their effects In here, we would mention the outline of water quality improvement facilities and their effects in reservoirs which we manage in Kizu River Integrated Office.

1) Selective intakes Selective Intakes were the facilities to enable withdrawal from desired level of water in the reservoirs. In normal time, selective intakes are utilized to withdraw warm water in surface layer, but in case of flood making water in reservoir muddy through inflow of turbid , or in case of algae bloom in surface layer, it is possible to withdraw clear water layer selectively through these facilities.

2) Aerating circulation facilities Aerating circulation facility has a technique to generate circulating flow using the buoyant force of air bubbles to transform the stratified status brought about by density differential (water temperature differential) and to help formation of circulating mixed layers on the surface of the reservoir. These mechanism can prevent proliferation of algae (blue-green algae in particular) by creating adverse environment for them (ex.:to lower the water temperature, reduction of sun-light and nutrient salts, etc). In here, we introduce a case of study in Takayama dam. According to the survey of the relation between surface water

-2- temperature and the cell number of Microcystis prepared by the data of periodical water quality examination in Takayama dam reservoir. It was confirmed that the cell number of Microcystis increased corresponding to surface water temperature became high. In particular, the cell number of Microcystis increased more than 100,000cells/ml in 50%, and more than 10,000cells/ml in another 50% in the case that water temperature was higher than 30 Celsius. The function of the aerating circulation facilities was proved to be effective by confirming that stratified status went to deeper than before the operation of the facilities. In addition, water temperature of upper layer averagely became higher than before, while that of surface part of the reservoirs became lower. In the case of Takayama dam reservoir, the number of Phormidium has greatly decreased and Microcystis also has decreased since 2003 when operation of aerating circulation facilities has started.

3) Separative curtain Separative Curtain control for reservoir is a method of utilizing density current in reservoir to reduce the inflow of nutrients into productive layer (surface layer) in downstream side of the curtains, through separation of upper and lower currents in surface layer in reservoir by cutoff curtains combined with Selective Intakes. In productive layer in downstream side of curtains, propagation of is prohibited due to exhausiton In here, we introduce a case of study in Shourenji dam. Based on monitoring survey of Shourenji Dam during 1996 to 2005,decrease of nutrients in downstream side of curtains and inhibition of algae bloom were confirmed as a result of cutoff effect of Separative Curtains.

4. Conclusion Maintaining the water qualities in dam reservoir is the most important works for us, and if it will cause significant problems to water utilization, it must affect a social. Therefore, it is necessary for management of dams to comply with control and conservation of water quality and volume in reservoirs precisely. However, it is still difficult to resolve water quality problem easily only through those measures within reservoirs, as there are yet many unknown factors regarding variation of water quality in reservoir, especially vicissitude

-3- of microorganism such as phytoplankton. In the future, in order to substantially improve our approach as monitoring survey.

-4- Measure for the water quality improvement in dam basin

Hiroyuki NAKAJIMA

Japan Water Agency (JWA)

Contents

1. Introduction 2.The situation of eutrophication in JWA dams reservoirs 3.Water quality improvement facilities and their effects 4.Conclusions

-5- 1.Introduction Target Areas of JWA

1.Introduction Eutrophication phenomenon (Algal blooms)

Blue-green algae red tide

-6- 2.The situation of eutrophication in JWA dams reservoirs

Total Phosphorus (T-P) and Chlorophyll-a and Classification of the Degree of Eutrophication

Item Oligotrophy Mesotrophy Eutrophy Remarks

Annual average total Vollenweider phosphorus levels < 10 mg/m3 10 to 30 mg/m3 > 30 mg/m3 1967 (mg/m3) Annual average chlorophyll a levels < 2.5 mg/m3 2.5 to 8 mg/m3 > 8 mg/m3 OECD 1982 (mg/m3)

2.The situation of eutrophication in JWA dams reservoirs

Number of facilities by eutrophication classification

Annual average T-P in the surface layer of dam reservoirs (27 facilities) Annual average chlorophyll-a in the surface layer of dam reservoirs (27 facilities)

100% 50 100% 25 80% 40 80% 20 60% 30 60% 15

（％） 40% 20 （mg/ m3） 40% 10 Average Ｔ－Ｐ Average 20% 10

Number of facilities 20% 5 0% 0 Average chlorophyll-a (mg/m3) 0% 0 '96 '97 '98 '99 '00 '01 '02 '03 '04 '05 Year '96'97'98'99'00'01'02'03'04'05Year >30mg/m3 10～30mg/m3 >8.0mg/m3 2.5～8.0mg/m3 <10mg/m3 Average <2.5mg/m3 Average

-7- 2.The situation of eutrophication in JWA dams reservoirs

Monthly and yearly changes in the number of facilities where had blue-green algae and fresh water red tide

20 Blue-green algae Freashwater red tide Blue-green algae Freashwater red tide 7 6 ilities 15 5 10 4 3 5 2 The numberfacilities of The number of fac 1 0 0

'96 '97 '98 '99Year '00 '01 '02 '03 '04 '05 Month 123456789101112

3.Water quality improvement facilities and their effects

Algal bloom Sunlight

Shading Ntorgen,Ph Selective intakes osphorus Selectiv Curtain Air Intake form

Aeration Bypass

The measure against eutrophication in dam reservoirs

-8- (1) Selective Intakes

Inflow Hot water Lower a water level selectiv Cold water Hotwater

Cold water

Discharge from low layer Lower a water level Cold water discharge (The decline of the water temperature)

Inflow Algal bloom Selectiv Hot water Inflow

Cold water Selectiv Lower a water level

Hot water Cold water

Discharge low layer with lower a water level Deep water depth (abiods Algal boom depth)

(2) Aerating circulation facilities

Mechanism

(1) Effect of keeping blue-green algae in the darkness

(2) Effect of nullifying the ability of blue-green algae to regulate buoyancy through control of water temperature gradient and vertical mixing of the upper layer

(3) Effects of spreading nutrient salts throughout the shallow layer

(4) Effect of encouraging the growth of diatoms and other types of algae

-9- (2) Aerating circulation facilities Outline

Sunlight日射 Inflow of nutrient salts流入栄養塩 Aerating曝気循環 circulation

Euphotic有光層 zone

Place暗所 of Circulation循環 darkness

Release of water 放流

(2) Aerating circulation facilities 1)Overview of the aeration circulation z The purpose of the aeration circulation is to restrain the explosive- occurrence of the algae ( phyto- ) such as blue-green alge by vertical-circulation on the dam with the air foam from the about 15 - 20 meter water depth.

-10- (2) Aerating circulation facilities 2)Vertical distribution of water temperature z Until 2002 when waterbloom was seen,water temperature of surface is high influence by outside temperature and thermocline is formed z But since 2004, waterbloom was not seen with aeration circuration ,and thermocline is not formed

Water Temrerature（℃） 16.0 18.0 20.0 22.0 24.0 26.0 28.0 30.0 32.0 34.0 125 Temp29.2℃ Temp33.9℃ 120 Temp31.9℃ 115 110 105 100 18-July-00 10:23 95 12-July-01 10:11 Lebel（E.L.m） 90 22-July-02 10:27 85 125 Temp 25.1℃ Temp 29.1 120 Temp 32.7℃ 115 110 105 15-July-2003 10:36 100 20-july-2004 9:42

Lebal（EL.m） 95 19-July-2005 10:44 90 85 Vertical water temperature distribution（July 2000～2005) Notes:Aba(standard point) field survey

(2) Aerating circulation facilities 3)Relation between Water temperature of dam lake surface(0.5m) and Microcystis number of cells z When water temperature of surface becomes high,Microcystis number of cells become more than 10,000 cells Microcystis number of cells and Wateremperature <1,000(cells/ml) <10,000(cells/ml) <100,000(cells/ml) >100,000(cells/ml) 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% ～15 ～20 ～25 ～30 30～ Times（time） 75(times) 38(times) 38(times) 33(times) 6(times) Water temrerature（℃） Water temperature and Microcystis number of cells Notes: result of regular water survey(per month)1989-2004(standard point surface 0.5m）

-11- (2) Aerating circulation facilities

4)The installation site of the aeration z Aeration installs about 1km interval from damsite to 3km of upper. z And operating the aeration from about 20m depth

Kizu river Hatta river

Dam site Aeration Tkayama Aeration bridge No1 Aeration Tukigase No2 bridge No3 Hachiman bridge Aeration ０ 1km No4 Aeration install site

Dam site →upper Takayama dam ※riverbed level：measures in 2002 140 135 Full water lebel (E.L.135.00m) 130 125 Standard point Takayama bridge Hachiman bridge Tsukigase bridge 120 Limit water level in flood season (E.L.117.00m) 115 110 Depth Depth Depth Depth Low water level(E.L.104.00m) 105 20m 20m 15m 15m

Level(E.L.m) 100 Discharge Aeratin No3 Aeration No4 95 AerationNo1Aeration No2 90 85 80 0 400 800 1,200 1,600 2,000 2,400 2,800 3,200 3,600 4,000 4,400 4,800 5,200 5,600 6,000 6,400 6,800 7,200 7,600 8,000 8,400 8,800 9,200 9,600 10,000

(2) Aerating circulation facilities 5)The operation of Aeration circulation z Four(4) aeration circulation were introduced from 2000 to 2003 z Operated one(1) aeration in 2002,two(2) aeration in 2003,and four(4) aeration continues since 2004

Item contents Aeraton No.1 2001 Installation year of aeration Aeraton No.2 2002 Aeraton No.3 2003 Aeraton No.4 2003 Initial cost(one aeration) About 65,000,000 yen running cost（electlic fee） About 2,700,000 yen 〃 （inspection） About 600,000 yen Aeration depth Air volume 0-20meter 5.6m3/min

Jan Feb Mar Aip May Jun Jul Aug Sep Oct Nov Dec year FMLFMLFMLFMLFMLFMLFMLFMLFMLFMLFMLFML 2002 One(1) aeration operates（No.１）

2003 Two(2) aeration operates（No.１ No.2）

2004 Four(4) aeration operates（No.１-No.4） Notes: F :First ten days M : Middle ten days L: Last ten days

-12- (2) Aerating circulation facilities

6)Number of cells about Microcystis in Takayama Dam z Before 2002, Microcystis number of cells was always 10,000cells/ml or more. but since 2003, Microcystis number of cells decrease The cell number of Microcystis dam site （surface）

100,000 90,000 80,000 70,000 60,000 50,000 40,000 30,000 Aeration set up 20,000 10,000

number of cells(cells/ml) of number 0 '95 '96 '97 '98 '99 '00 '01 '02 '03 '04 '05 '06 '07 The cell number of Phormidium in dam site （surface）

60,000 55,000 50,000 45,000 40,000 35,000 30,000 25,000 Aeration set up 20,000 15,000 10,000

number of cells (cells/ml) cells of number 5,000 0 '95 '96 '97 '98 '99 '00 '01 '02 '03 '04 '05 '06 '07

(2) Aerating circulation facilities

6)Number of cells about Microcystis in Takayama Dam z A lot of number of cells about Microcystis was seen on surface at 2000-2002, but since 2003, is not seen from surface to deep bottom Microcystis number of cells （cells/ml) 0 5,000 10,000 15,000 20,000 25,000 30,000 35,000 40,000 0 8,527,200cells/ml 265,032cells/ml 5

10

15 Depth（ｍ） 20

25

30 16-Aug-00 16-Aug-01 13-Aug-02 13-Aug-03 30-Aug-04 24-Aug-05

※Displayed with overlap at 2003 - 2005 Vertical distribution of number of Microcystis cells (August, 2000-2005)standard point 0.5, 2.5, 5.0, 10, and 25m

-13- (2) Aerating circulation facilities

7) Annual occurrence fresh water red tide and blue-green algewater bloom

z Water bloom was seen every year in summer (from July to September), but since 2003 which two aeration operates , water bloom isn’t seen

Fresh water red tide Blue-green alge Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 年次 FMLFMLFMLFMLFMLFMLFMLFMLFMLFMLFMLFML 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007

※Observation by watching

(2) Aerating circulation facilities

8)Status of blue-green alge(Dam site point 2000-2005) z Waterbloom was seen in 2000-2002 ,but was not seen in 2003-2005

◆Photograph (Dam site point August 2000－2005）

August 17 2000 waterbloom August 15 2001 waterbloom August 14 2002 waterbloom

August 2003 No waterbloom August 18 2004 No waterbloom August 24 2005 No waterbloom

-14- (3)Separative curtain

1) Outline of separative curtain in Shourenji dam

Funou river Funou river → 300Dam site upper 290 Separative curtain Benten Separative curtain 280 bridge 270 5m 260 250 240 Benten bridge level(E.L.m) 230 Dam site 220 210 200 0 200 400 600 800 Separative curtain 1,000 1,200 1,400 1,600 1,800 2,000 2,200

Shourenji bridge Kaochi bridge Shourenji river

Kajika bridge Dam site → upper Shourenji river ※water bed level :measure in 2004 300 290 Standard point Shourenji bridge Full water level E.L.277.0m 280 Separative curtain 270 Limit water level in flood season E.L.273.0m 5m 260 250 Low water level E.L.273.0m 240 Level (E.L.m) 230 220 210 200 0 200 400 600 800 5,200 5,400 5,600 4,800 5,000 1,600 1,800 2,000 2,200 3,400 3,600 3,800 4,000 1,000 1,200 1,400 2,400 2,600 2,800 3,000 3,200 4,200 4,400 4,600

(3)Separative curtain

① The measure against ② The measure against turbidity eutrophication in dam reservoirs in dam reservoirs

Upper stream Lower stream Upper stream Lower stream

Curtain Curtain

inflow Curtain inflow

-15- (3)Separative curtain

2)Function and effect of fractionation fences

† Prevention of expansion of blue-green algae and freshwater red tide † Reduction of nutrient flowing into the surface layer on the lower stream side of the curtain

Inflow of nutrient salts

Reservoir fractionation fence

Depletion of nutrient salts in the production layer of algae Lower stream

Bypassing of nutrient salts by selective intake Upper stream

Release of water

(3)Separative curtain

3) effects of curtain Installation of a reservoir Numbers of Peridinium cells fractionation fence 10000 Peridinium 1000

100

(cells/ml) 10

Number of cells of Number 1 '94'95'96'97'98'99'00'01'02'03 Changes over Time in the Numbers of Peridinium Cells

Upstream side of the fence lowerstream side of the fence 0 1 2 3 Lower stream 4 Upper stream Depth (m) Depth 5 April 19 6 0 2000 4000 6000 8000 10000 Numbers of Peridinium cells (Number of cells/ml)

Vertical Distribution of Numbers of Peridinium Cells (2002)

-16- 4.Conclusions

1.Measures,such as selective intakes,aeration circulation,separative curtain are effective for conservation of water quality in reservoirs. 2.It is necessary for dam management to effort for better operation over monitoring of effects. 3.We have to progress the technical innovation to supply people with good quality water.

Thank you

-17-