Question: What is listed in drainage basin when the type is Gravity and the reservoir surface is 34.36?
SQL: SELECT "Drainage basin (km²)" FROM "1-28702208-1" WHERE "Type" = 'Gravity' AND "Reservoir surface (ha)" = '34.36';

Question: What is the drainage basin when the reservoir suface is 6.14?
SQL: SELECT "Drainage basin (km²)" FROM "1-28702208-1" WHERE "Reservoir surface (ha)" = '6.14';

Question: What is the volume when the resrvoir is Tanes?
SQL: SELECT "Volume (hm³)" FROM "1-28702208-1" WHERE "Reservoir" = 'Tanes';