KAZALCI OKOLJA

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Key message
Neutral

While annual runoff in Slovenia was above the average in 2013 and 2014, it fell below the average in 2015. In the period 1961–2015, annual runoff was lower only in 1983, 2003 and 2011. The long-term downward trend of river runoff from the Slovenian territory currently persists.


This indicator shows the annual river balance of the Republic of Slovenia as a whole. The balance is composed of the river water inflow and runoff expressed in million m3/year. Both elements are calculated on the basis of mean annual discharge (flow, Qs) at the water measuring stations catching the majority of inflow and runoff of river water in and from Slovenia. The river balance of Slovenia represents one of the fundamental and more dynamic elements of the Slovenian water balance, which is also composed of precipitation, evaporation, changes in groundwater reserves and water use. Discharge measurements are reliable and well-established, meaning a longer time series of comparable data is available. Based on the accurate assessment of direct anthropogenic effects on the river regime, the river balance may serve as a good indicator of potential effects of climate change on the quantities of available water.


Charts

Figure VD03-1: Letna rečna bilanca Slovenije (neto odtok kot razlika med skupnim odtokom in dotokom )
Sources: 
Zbirka hidroloških podatkov Hidrolog, Agencija RS za okolje (2016)
Chart note: 

(* Podatki so bili popravljeni, več v poglavju Metodologija obdelave podatkov).

Show data

inflow

total run-off

net run-off

1961

12453

28699

16246

1962

15163

35475

20312

1963

14629

33294

18665

1964

11969

29531

17562

1965

20300

45265

24965

1966

16564

33854

17290

1967

14929

29115

14186

1968

12715

28472

15757

1969

12858

31449

18591

1970

15595

33382

17787

1971*

9408

22074

12666

1972

16409

36552

20143

1973

12512

26541

14029

1974

12081

28743

16662

1975

16325

32543

16218

1976

11028

26566

15538

1977

13551

29571

16020

1978

12898

29262

16364

1979

16075

35669

19594

1980

14103

32300

18197

1981

12652

26077

13425

1982

13152

29880

16728

1983

11069

22087

11018

1984

11965

28633

16668

1985

12754

28763

16009

1986

13098

28177

15079

1987

14189

31944

17755

1988

12499

26871

14372

1989

13414

26557

13143

1990

11602

26188

14586

1991

14611

30235

15624

1992

13736

28802

15066

1993

12566

25296

12730

1994

12033

25725

13692

1995

11746

28176

16430

1996

14737

32994

18257

1997

11706

24027

12321

1998

12344

28092

15748

1999

13873

29659

15786

2000

14299

30263

15964

2001

11586

26912

15326

2002

11458

24785

13327

2003

9253

18353

9100

2004

13087

30492

17405

2005

12938

26837

13899

2006

11821

24967

13146

2007

10550

22213

11663

2008

11639

27946

16307

2009

16834

33875

17041

2010

13362

34576

21214

2011

11133.78

21121.87

9988.08

2012

14867.65

28902.74

14035.10

2013

15311.83

35203.51

19891.68

2014

18995.99

43770.96

24774.97

2015

12027.64

24072.97

12045.33


Goals

  • Improved assessments of water quantities.
  • Providing a sufficient amount of drinking water for inhabitants.
  • Better availability of water intended for use (in the sense of reducing the effects of hydrological droughts) and improved state of water and water ecosystems.

Due to a great annual variability of river discharges, a longer time series of data is required for trend assessment. According to the operation of relevant water gauging stations, the most appropriate time series would be 1961–2000. Within the period 1981–2000 alone, the trend of decreasing runoff is barely noticeable. River runoff trends indirectly indicate an increased or decreased probability of low water occurrence (drought) and flood risk. However, annual river runoff trends do not always correspond to trends of high or low water level.

Most Slovenian rivers have torrential characteristics. This means that discharges tend to increase and decrease very quickly and that most water runs off at high water levels or during flooding. In most rivers, high water occurs in spring and autumn, usually as a result of thaws, snow melting and abundant precipitation. Intensive local precipitation causes local flooding of a torrential character that only affect smaller catchment areas. Torrential water courses are particularly vulnerable during periods of low discharge and hydrological drought, which are not distinctly seasonal and usually occur in late summer or early autumn. Hydrological droughts coincide with long periods of below-average precipitation and high air temperatures, which also results in agricultural droughts. As ecologically acceptable river discharges are maintained during such periods, shortages of irrigation water as well as deterioration of water quality may occur.

After two years with abundant quantities of water in Slovenia, the total annual water runoff in 2015 amounted to only 12,045 million m3 (382 m3/s). In the period 1961–2015, only four years were drier than 2015 (2003, 2011, 1983 and 2007). Although temperatures and precipitation exceeded the long-term average in 2015 (for more details see: T. Cegnar, 2015, Podnebne značilnosti leta 2015, Naše okolje, letnik XXII, št. 12; Agrometeorološki pregled leta 2015, Naše okolje, letnik XXII, št. 12), no catastrophic hydrological drought (in which river discharges were near or even below historic recorded minimums and the majority of Slovenia's territory would be affected), was recorded. The most affected by summer drought was south-western Slovenia, while in most of the country, the drought was periodically interrupted by summer thunderstorms. December was hydrologically dry as well. Droughts in October did not exceed annual return periods.

(further reading: I. Strojan, Hidrološko suho in toplo leto 2015, http://www.sos112.si/slo/tdocs/ujma/2016/030-038.pdf).

The periodical trend decreasing river discharge persists.


Data methodology for this indicator

Metodologija spremljanja, preverjanja ter obdelav urnih in dnevnih vodostajev, meritev pretokov, pretvorb vodostajev v pretoke, vzdolžnih izravnav in usklajevanja je ustaljena. Srednji letni pretoki so izračunani iz srednjih dnevnih pretokov. Ocenjuje se, da se izvorni podatki za ±5 % lahko razlikujejo od dejanskih vrednosti. Podatki o srednjih letnih pretokih (Qs) z vodomernih postaj so rezultat meritev in opazovanj v merilni mreži državnega monitoringa voda (upoštevana sta tudi podatka HE Dravograd in HE Formin, Dravske elektrarne Maribor). Leto 2014 je zadnje, za katerega imamo uradne (preverjene) podatke o pretokih z vodomernih postaj.

Ker državne meje ne sovpadajo z mejami (razvodnicami) vodozbirnih zaledij vodomernih postaj, rečni dotok in odtok, izračunan iz pretokov izbranih vodomernih postaj, ter dejanski rečni dotok in odtok Slovenije , niso skladni. Ocenjujemo, da podatki pokrijejo 93 % ozemlja Slovenije. Skladnost je pri različnih povodjih različna – za Posavje, ki mu pripada več kot polovica države, je skladnost 99 %, manjša od 90 % je le pri neposrednem zaledju Jadranskega morja brez Posočja, kjer znaša okoli 50 %.

Podatki za pretok Mure so usklajeni z Avstrijsko hidrološko službo. Na drugih vodomernih postajah, ki predstavljajo bilančne profile za dotok oz. odtok v Slovenijo in iz nje, teh uskladitev ni.

Source data base
Zbirka hidroloških podatkov Hidrolog, Agencija RS za okolje
Data administrator

Agencija RS za okolje (ARSO); Urad za hidrologijo in stanje okolja (oseba za stike: mag. Marjan Bat).

Date of data source summarization
01.12.2016
Time coverage
1961-2015
Geographical coverage
Slvoenija

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