| Year | Internal flow (million m3) | Inflow of surface water from neighbouring countries (million m3) |
|---|---|---|
| 1990 | 60619 | 30200 |
| 1995 | 34900 | 18700 |
| 2000 | 35700 | 23700 |
| 2001 | 32700 | 24500 |
| 2002 | 28000 | 19500 |
| 2003 | 26000 | 21300 |
| 2004 | 38300 | 21800 |
| 2005 | 42500 | 20000 |
| 2006 | 33700 | 26800 |
| 2007 | 33700 | 20000 |
| 2008 | 33500 | 25400 |
| 2009 | 44500 | 23100 |
| 2010 | 29800 | 41300 |
| 2011 | 35500 | 22800 |
| 2012 | 38000 | 24400 |
| 2013 | 44700 | 28800 |
| 2014 | 24900 | 16000 |
| 2015 | 18100 | 11700 |
| 2016 | 25800 | 16600 |
| 2017 | 37400 | 23000 |