Year	billion cubic meters
1961	506.5815
1962	514.7965
1963	514.7965
1964	514.7965
1965	514.7965
1966	514.7965
1967	514.7965
1968	514.7965
1969	514.7965
1970	514.7965
1971	514.7965
1972	514.7965
1973	514.7964999999999
1974	514.7965
1975	514.7965
1976	514.7965
1977	514.7965
1978	514.7964999999999
1979	514.7964999999999
1980	514.7965
1981	514.7965
1982	514.7965
1983	514.7965
1984	514.7965
1985	514.7965
1986	514.7965
1987	514.7965
1988	514.7965
1989	514.7964999999999
1990	514.7964999999999
1991	514.7965
1992	527.5065000000001
1993	527.5065000000001
1994	513.5065
1995	513.5065000000001
1996	513.5065000000001
1997	513.5065000000001
1998	513.5065000000001
1999	513.5065
2000	513.5065000000001
2001	513.5065000000001
2002	513.5065000000001
2003	513.5065000000001
2004	510.5065
2005	510.5065
2006	510.50649999999996
2007	510.5065
2008	510.5065
2009	510.5065
2010	510.5065
2011	510.5065
2012	510.50649999999996
2013	510.50649999999996
2014	510.5065
2015	510.5065
2016	510.50649999999996
2017	510.50649999999996
2018	510.50649999999996
2019	510.50649999999996
2020	510.5065