| Year | Total area (km2) |
| 1993 | 2.2863 |
| 1994 | 0.9901 |
| 1995 | 2.1625 |
| 1996 | 1.6757 |
| 1997 | 1.8709 |
| 1998 | 1.6089 |
| 1999 | 1.0289 |
| 2000 | 0.2797 |
| 2001 | 0.5056 |
| 2002 | 0.5238 |
| 2003 | 0.7507 |
| 2004 | 0.8578 |
| 2005 | 0.9714 |
| 2006 2007 | 0.4410 0.5941 |
| 2008 | 1.8715 |
| 2009 | 1.6602 |
| 2010 | 0.2690 |
| 2011 | 1.8540 |
| 2012 | 1.1030 |
| 2013 | 0.1935 |
| 2014 | 0.7325 |
| 2015 | 0.8775 |
| 2016 | 0.4578 |
| 2017 | 1.0609 |
| 2018 | 0.5872 |
| 2019 | 1.2378 |
| 2020 | 0.9250 |
| 2021 | 0.1779 |