You need 'real' water or just the reflection on ground? A water shader on ground won't work, as the planet is 'kind of solid'. If you want a 'real' puddle or stream, you'd have to use a masking method to displace the area down, and then add the terrain without the downward displacement to a local plane, or sphere (disable shadows) at height=0, and add a water shader there.
With a color adjust you can make all sorts of hard or soft variations of a (painted) mask.
If you want just the glistening and reflection of water, add a reflective shader to the masked surface layer in the terrain shader's line (below the rest of course). In that surface shader turn color off, and add a color adjust set at gamma 0.7 or so, to darken the wet area, then the reflective shader as child.
