Year billion cubic meters 1992 1.46 1993 1.4825 1994 1.505 1995 1.5275 1996 1.55 1997 1.5725 1998 1.595 1999 1.6175 2000 1.64 2001 1.62464 2002 1.60928 2003 1.59392 2004 1.57856 2005 1.5632 2006 1.5395 2007 1.5158 2008 1.4921 2009 1.4684 2010 1.4447 2011 1.4447 2012 1.4447 2013 1.4447 2014 1.4447 2015 1.4447 2016 1.4447 2017 1.4447 2018 1.4447 2019 1.4447 2020 1.4447