You should have atleast one matching StationId in all the tables otherwise it will not give you output
Run this in SQL Analyzer it will give you a single row output.
DECLARE @SluiceGateStatus TABLE (Id INT,StationId VARCHAR(20), GateStatus VARCHAR(20))
INSERT INTO @SluiceGateStatus VALUES(1,'St-01','open')
INSERT INTO @SluiceGateStatus VALUES(2,'St-02','close')
INSERT INTO @SluiceGateStatus VALUES(3,'St-10','open')
-------------------------------------------------------
DECLARE @DamTable TABLE (Id INT,StationId VARCHAR(20),WaterLevel DECIMAL,DamLevel DECIMAL)
INSERT INTO @DamTable VALUES(1,'St-01',34.7,56)
INSERT INTO @DamTable VALUES(2,'St-04',45,34)
INSERT INTO @DamTable VALUES(3,'St-05',2,8.8)
-------------------------------------------------------
DECLARE @PumpTable TABLE (Id INT,StationId VARCHAR(20),WaterLevel DECIMAL,PumpLevel DECIMAL)
INSERT INTO @PumpTable VALUES(1,'St-01',34.86,56.4)
INSERT INTO @PumpTable VALUES(2,'St-07',5.75,5.89)
--------------------------------------------------------
DECLARE @FlowTable TABLE (Id INT,StationId VARCHAR(20),WaterLevel DECIMAL,FlowLevel DECIMAL)
INSERT INTO @FlowTable VALUES(1,'St-08',34.86,2.0)
INSERT INTO @FlowTable VALUES(2,'St-01',3.5,34.7)
---------------------------------------------------------
DECLARE @StationsTable TABLE(Id INT,StationId VARCHAR(20),StationType VARCHAR(20),StationName VARCHAR(20),Latitude VARCHAR(50),Longitude VARCHAR(50),[State] VARCHAR(20),SluiceW_Level DECIMAL)
INSERT INTO @StationsTable VALUES(1,'St-01','Sluice Station','Sluice1','5.342611485','100.243359805','abc',3.5)
INSERT INTO @StationsTable VALUES(2,'St-02','Sluice Station','Sluice2','5.3442571','100.235514312','Pqr',14.65)
-----------------------------
SELECT ST.StationId, ST.StationName, ST. SluiceW_Level , SGS.GateStatus, DT.WaterLevel, DT.DamLevel, PT.WaterLevel, PT.PumpLevel, FT.WaterLevel, FT.FlowLevel
FROM @StationsTable AS ST INNER JOIN @SluiceGateStatus AS SGS
ON St.StationId = SGS.StationId INNER JOIN @DamTable AS DT
ON St.StationId = DT.StationId INNER JOIN @PumpTable AS PT
ON St.StationId = PT.StationId INNER JOIN @FlowTable AS FT
ON St.StationId = FT.StationId