LAKE G. DIMITROV

Eastern end of the lake


Photo: A.Kurata

A. LOCATION

• Kazanlak, Bulgaria.


• 42:36N, 25:19E; ca. 800 m above sea level.

B. DESCRIPTION

The man-made lake "G. Dimitrov" has been built 7 km upstream from the town of Kazanlak on the Tundja River in the Rosa Valley, which separates the Balkan mountain chain from the Sredna Gora mountains. The rock-filled dam is provided with thick concrete cover on the lake side and a road on its crest. The construction was completed in 1954 and the lake is managed by the office of "Lake and Cascades" Kazanlak Branch.
The watershed covers an area of 861 km2, and has an average altitude of ca. 800 m and a mean river gradient of 31.4%. The area is built of granite and granite-gneiss, old Tertiary sediments, diluvial and alluvial deposits. One may find traces of tectonic activities - fissured rocks, dislocation zones with sources of hot spring, etc. Its northern part includes the highest peak of Balkan Mountains, where thick and prolonged snow cover is characteristic. Steep slopes favor surface erosion development.
The lake is about 11 km2 in its surface area and the maximum depth reaches 40 m. It is located in a rich rural region that needs much clean water, and serves to regulate the seasonal turnoff of water supply according to the requirements of consumers - irrigation for fertile fields of both Kazanlak and Stara Zagora, chemical industry in the town of St. Zagora, and hydroelectric power plant.
Lake Dimitrov is also a great local centre for recreation and hot-spring cure because it is surrounded by a number of settlements and dense network of roads. There are good water-sport facilities including a paddle sport base on its northern bank (Q).

C. PHYSICAL DIMENSIONS (Q)

Surface area [km2]	11
Volume [km3]	0.14*
Maximum depth [m]	40
Mean depth [m]	12.7
Water level	Regulated
Normal range of annual water level fluctuation [m]	24
Length of shoreline [km]	26.3
Residence time [yr]	0.6
Catchment area [km2]	861

* Maximum.

D. PHYSIOGRAPHIC FEATURES

D1 GEOGRAPHICAL

• Sketch map: Fig. EUR-44-01.


• Names of main islands: None.


• Number of outflowing rivers and channels (name)
  3 (Tundja R. and 2 irrigation channels).

D2 CLIMATIC

• Climatic data at Kazanlak, 1931-1985

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Ann.
Mean temp. [deg C]	-0.7	1.3	4.8	10.6	15.3	18.9	31.4	21.0	16.8	11.2	6.4	1.6	11.6
Precipitation [mm]	41	33	31	46	75	76	65	48	34	45	49	45	588

• Number of hours of bright sunshine: 2,168 hr yr-1.


• Solar radiation: 13 MJ m-2 day-1.

Fig-EUR-44-01 Sketch map of the lake and its river network (Q).

• Water temperature [deg C]

Floating plot, 1954-1964
Depth [m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
0.5	3.2	2.8	6.0	11.3	18.2	22.5	24.8	25.0	21.2	16.8	10.6	5.6
5	3.4	2.8	5.3	9.8	15.1	18.8	21.5	22.8	19.7	14.8	10.3	6.0
10	3.7	2.7	5.1	8.6	13.0	16.2	18.9	21.4	19.1	14.8	10.2	5.9
20	3.7	3.0	4.9	7.8	11.4	14.2	16.9	19.5	18.5	14.9	10.7	6.2
B*	3.8	3.0	5.0	7.9	10.4	13.2	15.6	18.4	18.0	14.3	10.0	6.0

* Bottom.

• Mixing type: Monomictic.


• Notes on water mixing and thermocline formation
  After its formation the thermocline sinks downward due to both the heating of surface water layer and the intensive outflow.

Fig. EUR-44-02
The vertical water temperature distribution at the floating plot on 11 August 1987.

E. LAKE WATER QUALITY (Q)

E1 TRANSPARENCY [m]

Floating plot, 1986-1988
Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
-	-	-	2.4	2.1	1.6	1.2	-	1.2	1.2	-	-

E2 pH

Floating plot, 1971-1988
Depth [m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
S*1	-	7.1	6.6	6.8	6.5	6.7	6.6	6.9	6.9	7.6	6.8	6.4
20	-	-	-	-	-	-	-	6.5	-	-	6.5	-
30	-	-	-	6.0	6.0	-	-	-	-	-	-	-
B*2	-	6.5	6.5	7.0	6.5	6.5	7.0	6.7	7.0	7.5	6.8	6.8

*1 Surface. *2 Bottom.

E3 SS [mg l-1]

Floating plot, 1986-1988
Depth [m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
0	-	-	-	-	10	-	-	-	46	-	-	-
1	-	-	-	-	-	-	-	-	53	-	-	-
3	-	-	-	-	45	-	-	-	54	-	-	-
5	-	-	-	-	3	-	-	-	58	-	-	-
8	-	-	-	-	-	-	-	-	71	-	-	-
10	-	-	-	-	6	-	-	-	-	-	-	-
15	-	-	-	-	5	-	-	-	-	-	-	-
20	-	-	-	-	11	-	-	-	-	-	-	-
25	-	-	-	-	11	-	-	-	-	-	-	-
27*	-	-	-	-	115	-	-	-	-	-	-	-

* Bottom.

Fig. EUR-44-03
Vertical distribution of water temperature [deg C], suspended solid concentration (SSC) and suspended organic matter concentration (SOC) at the floating plot on June 30, 1987 (Q).

E4 DO [mg l-1]

Floating plot, 1986-1988
Depth [m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
0	-	-	-	-	10.5	-	-	-	-	-	-	-
3	-	-	-	-	10.2	-	-	-	-	-	-	-
5	-	-	-	-	10.8	-	-	-	-	-	-	-
10	-	-	-	-	10.0	-	-	-	-	-	-	-
15	-	-	-	-	10.5	-	-	-	-	-	-	-
20	-	-	-	-	9.3	-	-	-	-	-	-	-
23	-	-	-	-	10.3	-	-	-	-	-	-	-

E6 CHLOROPHYLL CONCENTRATION [micro l-1]

Floating plot, 1988
Depth [m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
0.25	-	-	-	-	4.26	-	-	-	-	-	-	-
1	-	-	-	-	4.49	-	-	-	-	-	-	-
3	-	-	-	-	4.86	-	-	-	-	-	-	-
5	-	-	-	-	3.24	-	-	-	-	-	-	-
7	-	-	-	-	2.22	-	-	-	-	-	-	-

E7 NITROGEN CONCENTRATION

• NO3-N [mg l-1]

Floating plot, 1986-1988
Depth [m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
0	-	-	-	-	3.4	-	-	-	0.8	-	-	-
1	-	-	-	-	-	-	-	-	1.4	-	-	-
3	-	-	-	-	-	-	-	-	1.6	-	-	-
5	-	-	-	-	-	-	-	-	3.8	-	-	-
10	-	-	-	-	4.65	-	-	-	-	-	-	-
20	-	-	-	-	3.00	-	-	-	-	-	-	-
30	-	-	-	-	0.90	-	-	-	-	-	-	-

• NH4-N [mg l-1]

Floating plot, 1986-1988
Depth [m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
0	-	-	-	-	0.24	-	-	-	0.08	-	-	-
1	-	-	-	-	-	-	-	-	0.10	-	-	-
3	-	-	-	-	-	-	-	-	0.10	-	-	-
5	-	-	-	-	-	-	-	-	0.12	-	-	-
10	-	-	-	-	0.80	-	-	-	-	-	-	-
20	-	-	-	-	1.00	-	-	-	-	-	-	-
30	-	-	-	-	1.98	-	-	-	-	-	-	-

E8 PHOSPHORUS CONCENTRATION

• PO4-P [mg l-1]

Floating plot, 1988
Depth [m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
0	-	-	-	-	0.03	-	-	-	-	-	-	-
10	-	-	-	-	0.04	-	-	-	-	-	-	-
20	-	-	-	-	0.04	-	-	-	-	-	-	-
30	-	-	-	-	0.03	-	-	-	-	-	-	-

E9 CHLORIDE CONCENTRATION [mg l-1]

Floating plot, 1986-1988
Depth [m]	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
0	-	-	-	-	14.2	-	-	-	22.2	-	-	-
1	-	-	-	-	-	-	-	-	26.9	-	-	-
3	-	-	-	-	-	-	-	-	22.8	-	-	-
5	-	-	-	-	-	-	-	-	25.1	-	-	-
10	-	-	-	-	14.2	-	-	-	-	-	-	-
20	-	-	-	-	12.8	-	-	-	-	-	-	-
30	-	-	-	-	14.8	-	-	-	-	-	-	-

F. BIOLOGICAL FEATURES (Q)

F1 FLORA

Floating plot, May 1988

• Phytoplankton
  Pyrrophyta (Cryptomonas sp.), Bacillariophyta (Cyclotella sp.), Cyanophyta, Chlorophyta.

F2 FAUNA

• Zooplankton

Cyclops strenuus, Daphnia pulex, D. longispina, Monia recrostris, Bosmina longirostris, Ceriodaphia setosa, Chydorus sp., Leydigia sp., Brachionus pala, B. angularis.
• Benthos

Chironomus plumosus, C. semireductus, Cryptochironomus ex. gr. conjugens, C. gr. camptolabis, Polypedilum ex. gr. nebuculosum, Polypedilum sp., Paratendipes gr. albimanus.
• Supplementary notes on the biota

An 1988 search showed a fair uniformity in the biological parameters throughout the lake due to the continuous water outflow that produces a permanent water current going downstream and temporary upstream currents. They both mix up the water.

F3 PRIMARY PRODUCTION RATE

Floating plot, May 1988
[m]	[g 02 m-2]
0.0	0.69
0.5	0.80
1.0	0.43
3.0	0.28
5.0	0.14
7.0	1.00

F5 FISHERY PRODUCTS

• Annual fish catch [metric tons]
  1954-1964: 30.
• Fishery products other than fish: None.

G. SOCIO-ECONOMIC CONDITIONS (Q)

G1 LAND USE IN THE CATCHMENT AREA (1985)

	Area [km2]	[%]
Natural landscape
- Woody vegetation	448	52
- Herbaceous vegetation	103	12
Agricultural land
- Crop field	241	28
- Pasture land	34	4
Residential area	34	4
Total	861	100

• Types of important woody vegetation
  Low-stemmed forest (beech, oak), pine forest.
• Main kinds of crops and/or cropping systems
  Rose and lavender (for perfume oil), wheat and maize.
• Levels of fertilizer application on crop fields: Moderate.


• Trends of changes in land use in recent years: None.

G2 INDUSTRIES IN THE CATCHMENT AREA AND THE LAKE

	No. of persons engaged [%]	Main products or major industries
Primary industry	40	Mash & tool production, timber industry
- Crop production	24
- Others	9
Secondary industry	12	Energy production, textile, food industry
Tertiary industry	15

G3 POPULATION IN THE CATCHMENT AREA (1986)

	Population	Population density [km-2]	Major cities (population)
Urban	35,000
Rural	60,000		None
Total	95,000	110

H. LAKE UTILIZATION (Q)

H1 LAKE UTILIZATION

Source of water, sightseeing and tourism, recreation (swimming, sport-fishing, yachting) and fisheries.

H2 THE LAKE AS WATER RESOURCE (1985)

	Use rate [m3 yr-1]
Domestic	None
Irrigation	118,000,000
Industrial	44,000,000
Power plant	100 MWh

I. DETERIORATION OF LAKE ENVIRONMENTS AND HAZARDS (Q)

I1 ENHANCED SILTATION

• Extent of damage: Not serious.


• Supplementary notes
  The sedimentation rate is still larger than the target rate decreasing rather slowly.

I2 TOXIC CONTAMINATION

• Main contaminants and their concentrations

Floating plot, May, 1988
Names of contaminants	Concentration [ppm]
	Water	Sediments
Mn	0.021	0.088
Cu	0.008	0.0044
Pb	0.001	0.0067
Zn	0.0285	0.0161
Fe	0.132	3.30
Cd	0.0	0.0004

• Environmental quality standards for contaminants in the lake: Present.


• Food safety standards or tolerance limits for toxic contaminants in the
  lake: Present.

I3 EUTROPHICATION

• Nuisance caused by eutrophication
  Unusual algal bloom (Cyanophyta, Chlorophyta, Chlamydomonas, Bacillariophyta).
• Nitrogen and phosphorus loadings to the lake [g l-1] (1988)

Sources	Industrial	Agricultural	Natural
T-P	10.64	28.02	4.29

I4 ACIDIFICATION

• Extent of damage: Detected but not serious.


• Past trends in hydrogen ion concentration in lake water
  Since 1976 pH changed from 7.5-7.8 to 6.2-6.4.

I5 OTHER HAZARDS

None.

J. WASTEWATER TREATMENTS

J1 GENERATION OF POLLUTANTS IN THE CATCHMENT AREA (Q)

(c) Limited pollution with wastewater treatment.

J3 SANITARY FACILITIES AND SEWERAGE

• Percentage of municipal population in the catchment area provided with
  adequate sanitary facilities (on-site treatment systems) or public sewerage: 92%.
• Municipal wastewater treatment systems
  No. of tertiary treatment systems: 2.
  No. of secondary treatment systems: 2.
  No. of primary treatment systems: 2.

K. IMPROVEMENT WORKS IN THE LAKE

K1 RESTORATION (Q)

River bed dredging at the mouth for the dam safety.

L. DEVELOPMENT PLANS (Q)

Since 1970 - Recreation development.

M. LEGISLATIVE AND INSTITUTIONAL MEASURES FOR UPGRADING LAKE ENVIRONMENTS (Q)

M1 NATIONAL AND LOCAL LAWS CONCERNED

• Names of the laws (the year of legislation)


1. The law for water, air and soil protection (1963)
2. The law for environment protection (1967)
3. The law for water (1969)
• Responsible authorities


1. Local authority
2. Ministry of Energetics
3. Ministry of Agriculture and Forestry
• Main items of control


1. Quality and quantity of water inflow
2. Quality of water outflow
3. Rate of lake sedimentation

M2 INSTITUTIONAL MEASURES

1. State Committee for Environment Protection
2. Local authority
3. Ministry of Health
4. Bulgarian Academy of Sciences

M3 RESEARCH INSTITUTES ENGAGED IN THE LAKE ENVIRONMENT STUDIES

1. Institute for Hydrology and Meteorology, Sofia
2. Institute for Water Management, Sofia
3. Environment Protection Research Centre, Sofia

N. SOURCES OF DATA

17. Questionnaire filled by Dr. G. Gergov, Institute for Hydrology and Meteorology, Sofia, Bulgaria.
1. Handbook of the Bulgarian Rivers, vol. I (1957), II (1958), XVI (1964). Science and Art, Sofia.
2. Results from both the Economy and Technical Exploitation of the Bulgarian Large Man-made Lakes (1965). Technica, Sofia.
3. Statistical Yearbook for Bulgaria (1986). Sofia.
4. The data from field measurements on the man-made lake "G. Dimitrov" supported by a grant of the Ministry of Culture, Science & Education, No. 747/87.