Our water layer - for drawing lakes, puddles, rivers and so on - is going to use a lot of layer styles, although we do need to start with a layer mask.
- Create a new layer and call it "Water".
- Fill it with a suitable watery colour. I use a nice, deep blue (#363847).
- Make a layer mask and lock the water layer.
- Delete everything on the layer mask so the map isn't flooded.
- Using a large, hard edged brush, draw a river from the left hand side of the map to the right - just so we can see what's happening as we continue.
3.1 The River Bank
Our first task is to create a river bank - a sloping effect on the dirt around the water. For this, we can use a layer style.
- Click on the water layer - not the layer mask.
- Go to the "Layer" menu, then "Layer styles" and finally "Bevel & Emboss".
- Set it up as pictured below.
This creates a gently sloping riverbank around the water. However, for extra realism, we can also have the bank cast a slight shadow on the water.
- Go to the "Layer" menu, then "Layer styles" and finally "Inner shadow".
- Set it up as pictured below.
Your river should now look something like this.
3.3 Shallow Water
Next we need to create the appearance of shallow water near the edge, gradually getting deeper. For this, we can use an inner glow.
- Go to the "Layer" menu, then "Layer styles" and finally "Inner glow".
- Set it up as pictured below.
The result should look like this.
We have a problem.
The inner glow works fine and it's an effect I really like, but because the edge of the map is also the edge of the river, we get solid, straight bars of inner glow on either end of the map. This is one of the quirks of using Photoshop for this sort of thing and it's an effect which will pop up for a few of the terrain layers we will be creating. However, it's fairly easy to deal with. We need to make the edge of the map different to the edge of the canvas.
- Make sure your background colour is white.
- Go to the "Image" menu and select "Canvas size".
- Increase the width and height by two inches (an inch on each side).
- Unlock and then select the water layer (not the layer mask for the layer).
- Fill the gap around the edge with the same blue you used for the rest of the water.
- Re-lock the water layer and select the water layer's mask.
- Fill the gap around the edge in black. This will also wipe out your river but that's okay for the moment.
- Redraw your river on the water's layer mask but, this time, go past the edge of the map and right out to the edge of the canvas. It should look a bit like this, although I added a border around the image to make the canvass edges clear.
This works, sort of. The white bars of the inner glow are now off the edge of the map. However, we can tidy up a bit more.
- Select the contents of the grass layer. On the Mac, hold down the command key and click on the grass layer's thumbnail. On a Windows computer, hold down control instead.
- Go to the "Select" menu and pick "Inverse".
- Create a new layer right at the top of your layer stack and call it "Border".
- Use the paint bucket tool to fill the selected area in white.
The net effect of all this is that the river goes off the edge of the map so that we can't see the inner glow where the canvas stops. We then created a one inch white border to cover this up. Your map should look something like this. (Again, I added a border for clarity.)
3.4 Ripples
This has been a lot of work to produce a simple river and it looks fine as is, but there is just one more effect I like to add.
- Go to the "Layer" menu, then "Layer styles" and finally "Pattern Overlay".
- Set it up as pictured below.
Photoshop has a lot of patterns to mess around with here but they're hard to find. You need to click on the arrow next to the pattern thumbnail, then the tiny little cog, and then you can select from a set of pattern collections. The one you want is at the end of the second row in the "Patterns" collection.
Your final river should look something like this.
3.5 Drawing with Water
When drawing water, use a hard edged round brush and remember that, if the water goes off the edge of the map, you need to continue the water under the white border to prevent that white bar effect.
The banks of the water body should be dirt since grass just looks odd. If you do have a grass landscape, clear the banks with the maple leaf brush to create the raggedy, organic effect.
Depending on the environment, you can also tweak the water colour - brown for a swamp, turquoise for a tropical sea and although I've not needed it myself, I suspect you can create a reasonable lava effect too (you might want to add a orange outer glow layer effect, though).
Finally, if your computer is struggling, some of the water effects can be switched off without too much problem. The shadow, for example, is a subtle effect which doesn't impact the overall look that much.