There is. But I have forgotten the CVAR.
Try this macro:
Code:
/console groundEffectDensity 1
/console groundEffectDist 1
/console detailDoodadAlpha 1
/console horizonfarclip 1
/console farclip 4
/console smallcull 0.040000
/console characterAmbient 1
/console skycloudlod 1
If this is too much, try groundEffect one's only. To revert to appropriate settings you will need to delete the CVAR's from your WTF\config.wtf settings (I think these settings are stored here, not sure).
Shadows/light/water effects take up the most CPU, so you should try reducing them first.
edit: Also moved to WoW General.