World around us: NDVI vs NDWI

This checkerboard picture is a satellite photo of Priest river in the northern Idaho.

http://owm.io/sql-viewer?select=b4%2Cb3%2Cb2&from=s2&where=day%3D2016-07-21&op=&order=&color=gamma%281.5%29&lat=48.42&lon=-116.86&zoom=13#

“The land shown here is now managed for wildlife and for timber harvesting. The white patches reflect areas with younger, smaller trees, where winter snow cover shows up brightly to the astronauts. Dark green-brown squares are parcels of denser, intact forest. The checkerboard is used as a method of maintaining the sustainability of forested tracts while still enabling a harvest of trees.” (с) EARTH OVSERVATORY

http://earthobservatory.nasa.gov/IOTD/view.php?id=89541&eocn=home&eoci=iotd_previous

It's interesting to see this area from the point of view of vegetation (NDVI) and water (NDWI) indexes.As for NDVI index, areas with a grass and young, low trees, almost no visible on the background of the "normal" forest.

http://owm.io/sql-viewer?select=b8%2Cb4&from=s2&where=day%3D2016-07-21&op=ndvi&order=&color=&lat=48.42&lon=-116.86&zoom=13#

But in the NDWI model the difference is obvious. 

 You can see the distribution of the vegetation in more details using VANE Query tool with the {color} parameter. In this case it's color=brightness>350,brightness<10000