What was the least volume recorded in 2011-12 when 2008-09 had 21652?
CREATE TABLE "table1_1470706_1" (
  "station_name" text,
  "2002_03" real,
  "2004_05" real,
  "2005_06" real,
  "2006_07" real,
  "2007_08" real,
  "2008_09" real,
  "2009_10" real,
  "2010_11" real,
  "2011_12" real
);
SELECT MIN("2011_12") FROM "table1_1470706_1" WHERE "2008_09"=21652;