water tesion

Water tension is due to the presence of hydrogen bonds between water molecules.

The addition of NaCl increases the concentration of ions. These sodium cations and chloride anions help water molecules to attract each other, making the interaction stronger.

圖片參考：http://us.f6.yahoofs.com/hkblog/d1WWTL6FGRtxq8qXRSSQITaWWQVB_2/blog/20090902105254305.jpg?ib_____DoLHJj1SY

The attraction between water molecules becomes stronger because water molecules can form ion-dipole interaction with sodium ions and chloride ions.

I donot know what you mean water tension , how can you measure the attraction force within the water molecules & the dissolved matter . If the water tension is really water surface tension then you can continue .
The water surface tension is affected by adding salt in water . The surface tension is decreased slightly but after adding more salt will not make any difference . When you add surfactants into water , the surface tension (73 dynes/cm) will be lowered to about 20-50 dynes/cm .