<p>I am pretty the real answer is in how well known the waterways are, which distorts perceptions of which side of the mountains really has more flowing.</p>

<p>The rivers on the <a href="https://www.youtube.com/watch?v=Tmv_8j_UnTs" rel="nofollow noreferrer">leeward</a> side of mountains typically go on to travel large distances, and so as they continue, tributary waterways gradually merge, and so such rivers end up having gathered water from huge areas, often therefore being very large and wide further down towards their mouthes.</p>

<p>But the thing is that near the mountains, I believe you'll actually notice that waterways on each side of the ridges are fairly similar... and indeed that that the windward side tends to have if anything more rivers and streams.  It's just they simply don't go very far before reaching the ocean... so they aren't able to merge together from large collections into bigger rivers.  And thus they also aren't very famous because there are so many of them and they're so short and unremarkable in width that people outside the local area just haven't heard of them.</p>

<p>I couldn't quickly find great map tools or GIS placefiles for India that would allow us to easily turn enhance the view and select layers so we could highlight the waterways details well.  But <a href="https://www.openstreetmap.org/#map=10/10.8124/76.4851" rel="nofollow noreferrer">OpenStreetMap</a> at least has water features of many widths and fames included on a map even when zoomed out a fair bit to show the broader balance.  So that allowed a sort of quick snapshot, which I took for around southern Karnataka and nearby areas in the south:</p>

<p><a href="https://i.sstatic.net/Vp2sP.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/Vp2sP.png" alt="OSM waterways"></a></p>

<p>I then sketched in the rough boundary of the Western Ghats (in brown) using the great <a href="http://topographic-map.com" rel="nofollow noreferrer">Topographic-map.com</a> and also the rough path of the Kaveri River (which Wikipedia seems to suggest is probably the most well-known river in the region?), as well as some of its sizable tributaries (in blue) within the flatter lands.</p>

<p>But click on it to open the picture full screen and look past those bigger lines I drew on and focus instead on the light blue lines OSM uses to show waterways, I think you'll notice that approaching the mountains, there's plenty of waterways flowing from the western edge of the Ghats to the Arabian Sea.  I very much do wish we had a better map source that could color-code rivers by width, and stand them out more amongst the other geographic features.  But I hope you'll find this clearly enough shows that the rivers aren't nearly all on the eastern side, it's just that the ones there flow such a long way that by Tiruchirappalli, they have merged into one large river... which all those waterways west of the Ghats never get the opportunity to do.  But there's a lot of water flowing down the western sides of the Ghats.</p>

<p>And if you look around the <a href="https://www.openstreetmap.org/#map=10/10.8124/76.4851" rel="nofollow noreferrer">OpenStreetMap display of India at the same zoom</a>, I believe you'll convince yourself this is the same case up and down the west coast.</p>

<p>And that that is also true in many other places, like in <a href="https://www.openstreetmap.org/#map=8/-37.184/-71.340" rel="nofollow noreferrer">Chile/Peru along the Andes</a> (where the mighty Amazon flows east).</p>

<p><strong>More water flows down the near (windward) side of the mountains... the rivers there just aren't able to continue on far enough to become grand rivers and reach fame to be put on the national maps or school quizzes.</strong></p>

CC BY-SA 4.0
2018-08-08T13:02:21.917Z
You're certainly welcome to [downvote!] :-D But I think that is sort of my point - the rivers flowing east have large areas to gather additional water, be it from mountains further afield, or regimes not influenced by rain shadows. Funny enough, as I edited, I actually wished I would've done something like the Tungabhadra instead, to be more central/representative... but I'd gone through the creation process already, and figured the Kaveri well enough met my main idea that I'd leave it be. If you're pretty convinced I should try another river, certainly let me know will see what I can do :)
JeopardyTempest
CC BY-SA 4.0
2018-08-08T14:27:16.133Z
@gansub I'm not sure he really considers the distinction :-D Being taught rain shadows seems to either be an intro college course (meteorology/climatology/similar), or more likely a secondary school phys sci or younger general sci, at least in our part of the world. So I think he may just see that maps show the big rivers to the east of the mountains in India/other places and wonder how. Indeed, if that's so though, it's almost a detail worth highlighting as a separate answer - that the impact of mountains has a limited extent, and most water in the biggest rivers isn't from mountainous areas?
JeopardyTempest
CC BY-SA 4.0
2018-08-10T10:20:52.657Z
There seems to be an assumption in this answer that mountain ranges are close to a west coast?
Semidiurnal Simon
CC BY-SA 4.0
2018-08-10T15:27:09.557Z
@SemidiurnalSimon Indeed, that would be the prominent wind direction for many areas I'd be thinking of.  And where many of the more prominent coastal ranges are?  But I certainly wouldn't say it's a requirement (and why I tried to use windward and leeward instead of west/east).  And would expect the same for east coast ranges in the Tropics/Arctic or other directions if wind is regionally disparate from the global circulation core ideas.
JeopardyTempest
CC BY-SA 4.0
2018-08-12T11:39:54.227Z
@JeopardyTempest quite right, sorry. What I should have said is that there's an assumption that mountain ranges are close to a coast on their windward side. While this is true in the Americas, I'm not convinced that it's generally the case.
Semidiurnal Simon
CC BY-SA 4.0
2018-08-08T12:39:56.073Z
2018-08-08T12:39:56.073Z
JeopardyTempest
<p>My teacher explained that when wind coming from the ocean gets blocked by a mountain it makes rain on one side of the mountain, like in the image below. This rain leads to the creation of rivers.</p>

<p><a href="https://i.sstatic.net/nJyGO.jpg" rel="noreferrer"><img src="https://i.sstatic.net/nJyGO.jpg" alt="enter image description here"></a><br>
<sup><sub>(found on <a href="https://www.google.com/search?hl=en&amp;q=relief%20rainfall%20is%20formed&amp;tbm=isch&amp;tbs=simg:CAQSlgEJzOn96iUL1rAaigELEKjU2AQaBAgVCAsMCxCwjKcIGmEKXwgDEievE4AJywhMzAjhCNUCsROmE80HuDekK5k55jeJK9wpjCubKZo5jSsaMD-umUkpWtJS32PQ-KPM1eEMMK1sfrNZS1lJIzcTf3gtKkbTJDOM5mAtf2BFbEyeLyAEDAsQjq7-CBoKCggIARIEn5ArXww&amp;sa=X&amp;ved=0ahUKEwji3eKT-dzcAhUMPN8KHSlsC3EQwg4IJigA&amp;biw=1600&amp;bih=801#imgrc=vxUDQUOArq1QeM:" rel="noreferrer">Google Images</a> to be on numerous websites, difficult to determine original source)</sub></sup></p>

<p>My question is: Why is it that rivers sometimes run from the other side of the mountain inland instead of being on the same side of the mountain where the greater rain happens, traveling back to the sea?</p>

<p>One example of this is when monsoon winds coming from <a href="https://www.mapsofindia.com/maps/india/hillranges.htm" rel="noreferrer">the Arabian Sea hit the Indian Western Ghats, it makes rivers which travel to the east instead of traveling to the west</a>.</p>

CC BY-SA 4.0
2018-08-08T07:29:08.603Z
Did you draw that image yourself!?!  If so, it's pretty good for a quick drawing.
JeopardyTempest
CC BY-SA 4.0
2018-08-08T07:33:48.660Z
@JeopardyTempest, No, from Google Images.
MrDi
CC BY-SA 4.0
2018-08-08T07:46:02.027Z
Ok, I tried to make improvements for that and minor grammar things... if you don't think the changes helped, you're certainly welcome to change it back!
JeopardyTempest
CC BY-SA 4.0
2018-08-08T08:42:31.733Z
Interesting question! The straightforward answer is that some rain happens on the other side, otherwise there would be no rivers there. The more interesting question is perhaps why this is...
Semidiurnal Simon
<wind><rainfall><rain><orography>
Why do rivers sometimes travel down the opposite side of the mountains from where the rain happens?
MrDi
# Why do rivers sometimes travel down the opposite side of the mountains from where the rain happens?

(Asked by: username_0 on 2018-08-08)

My teacher explained that when wind coming from the ocean gets blocked by a mountain it makes rain on one side of the mountain, like in the image below. This rain leads to the creation of rivers.

[![enter image description here](https://i.sstatic.net/nJyGO.jpg)](https://i.sstatic.net/nJyGO.jpg)  
(found on [Google Images](https://www.google.com/search?hl=en&q=relief%20rainfall%20is%20formed&tbm=isch&tbs=simg:CAQSlgEJzOn96iUL1rAaigELEKjU2AQaBAgVCAsMCxCwjKcIGmEKXwgDEievE4AJywhMzAjhCNUCsROmE80HuDekK5k55jeJK9wpjCubKZo5jSsaMD-umUkpWtJS32PQ-KPM1eEMMK1sfrNZS1lJIzcTf3gtKkbTJDOM5mAtf2BFbEyeLyAEDAsQjq7-CBoKCggIARIEn5ArXww&sa=X&ved=0ahUKEwji3eKT-dzcAhUMPN8KHSlsC3EQwg4IJigA&biw=1600&bih=801#imgrc=vxUDQUOArq1QeM:) to be on numerous websites, difficult to determine original source)

My question is: Why is it that rivers sometimes run from the other side of the mountain inland instead of being on the same side of the mountain where the greater rain happens, traveling back to the sea?

One example of this is when monsoon winds coming from [the Arabian Sea hit the Indian Western Ghats, it makes rivers which travel to the east instead of traveling to the west](https://www.mapsofindia.com/maps/india/hillranges.htm).

**Tags:** wind, rainfall, rain, orography

> **Comments:**
> **username_1**: Did you draw that image yourself!?!  If so, it's pretty good for a quick drawing.  
> **username_0**: @username_1, No, from Google Images.  
> **username_1**: Ok, I tried to make improvements for that and minor grammar things... if you don't think the changes helped, you're certainly welcome to change it back!  
> **username_2**: Interesting question! The straightforward answer is that some rain happens on the other side, otherwise there would be no rivers there. The more interesting question is perhaps why this is...  

---

## 1 answers

### Answer by username_1 on 2018-08-08. Score: 1

I am pretty the real answer is in how well known the waterways are, which distorts perceptions of which side of the mountains really has more flowing.

The rivers on the [leeward](https://www.youtube.com/watch?v=Tmv_8j_UnTs) side of mountains typically go on to travel large distances, and so as they continue, tributary waterways gradually merge, and so such rivers end up having gathered water from huge areas, often therefore being very large and wide further down towards their mouthes.

But the thing is that near the mountains, I believe you'll actually notice that waterways on each side of the ridges are fairly similar... and indeed that that the windward side tends to have if anything more rivers and streams. It's just they simply don't go very far before reaching the ocean... so they aren't able to merge together from large collections into bigger rivers. And thus they also aren't very famous because there are so many of them and they're so short and unremarkable in width that people outside the local area just haven't heard of them.

I couldn't quickly find great map tools or GIS placefiles for India that would allow us to easily turn enhance the view and select layers so we could highlight the waterways details well. But [OpenStreetMap](https://www.openstreetmap.org/#map=10/10.8124/76.4851) at least has water features of many widths and fames included on a map even when zoomed out a fair bit to show the broader balance. So that allowed a sort of quick snapshot, which I took for around southern Karnataka and nearby areas in the south:

[![OSM waterways](https://i.sstatic.net/Vp2sP.png)](https://i.sstatic.net/Vp2sP.png)

I then sketched in the rough boundary of the Western Ghats (in brown) using the great [Topographic-map.com](http://topographic-map.com) and also the rough path of the Kaveri River (which Wikipedia seems to suggest is probably the most well-known river in the region?), as well as some of its sizable tributaries (in blue) within the flatter lands.

But click on it to open the picture full screen and look past those bigger lines I drew on and focus instead on the light blue lines OSM uses to show waterways, I think you'll notice that approaching the mountains, there's plenty of waterways flowing from the western edge of the Ghats to the Arabian Sea. I very much do wish we had a better map source that could color-code rivers by width, and stand them out more amongst the other geographic features. But I hope you'll find this clearly enough shows that the rivers aren't nearly all on the eastern side, it's just that the ones there flow such a long way that by Tiruchirappalli, they have merged into one large river... which all those waterways west of the Ghats never get the opportunity to do. But there's a lot of water flowing down the western sides of the Ghats.

And if you look around the [OpenStreetMap display of India at the same zoom](https://www.openstreetmap.org/#map=10/10.8124/76.4851), I believe you'll convince yourself this is the same case up and down the west coast.

And that that is also true in many other places, like in [Chile/Peru along the Andes](https://www.openstreetmap.org/#map=8/-37.184/-71.340) (where the mighty Amazon flows east).

**More water flows down the near (windward) side of the mountains... the rivers there just aren't able to continue on far enough to become grand rivers and reach fame to be put on the national maps or school quizzes.**

> **Comments:**
> **username_1**: You're certainly welcome to [downvote!] :-D But I think that is sort of my point - the rivers flowing east have large areas to gather additional water, be it from mountains further afield, or regimes not influenced by rain shadows. Funny enough, as I edited, I actually wished I would've done something like the Tungabhadra instead, to be more central/representative... but I'd gone through the creation process already, and figured the Kaveri well enough met my main idea that I'd leave it be. If you're pretty convinced I should try another river, certainly let me know will see what I can do :)  
> **username_1**: @gansub I'm not sure he really considers the distinction :-D Being taught rain shadows seems to either be an intro college course (meteorology/climatology/similar), or more likely a secondary school phys sci or younger general sci, at least in our part of the world. So I think he may just see that maps show the big rivers to the east of the mountains in India/other places and wonder how. Indeed, if that's so though, it's almost a detail worth highlighting as a separate answer - that the impact of mountains has a limited extent, and most water in the biggest rivers isn't from mountainous areas?  
> **username_2**: There seems to be an assumption in this answer that mountain ranges are close to a west coast?  
> **username_1**: @username_2 Indeed, that would be the prominent wind direction for many areas I'd be thinking of.  And where many of the more prominent coastal ranges are?  But I certainly wouldn't say it's a requirement (and why I tried to use windward and leeward instead of west/east).  And would expect the same for east coast ranges in the Tropics/Arctic or other directions if wind is regionally disparate from the global circulation core ideas.  
> **username_2**: @username_1 quite right, sorry. What I should have said is that there's an assumption that mountain ranges are close to a coast on their windward side. While this is true in the Americas, I'm not convinced that it's generally the case.  

---

