GIS analysis

[Nagesh Aras]

Hi


I would like help from users or QGIS (or ArcGIS) in analyzing the sewage scenario in Bangalore.

The rough idea is as follows:

1. We have the BWSSB STP locations and their capacity.
2. We have the rain precipitation figures
3. By analyzing the terrain (e.g. Digital Elevation Model from ISRO), can we find the watersheds (catchment areas) for each STP?
4. Can we estimate how much sewage and rainwater each STPwill get on a day-to-day (or month-to-month) basis?

Thanks in advance!

Regards,
Nagesh
9448239985

[Devdatta Tengshe]

Having some experience with Urban Hydrology, (as well as having worked on BISON for BWWSB) here is what I can tell you.

1) For most purposes, running a Simple trace on the Sewage Network by itself is usually more than enough. In most cases, the STP has more capacity than the capacity of the drains leading to it.

2) Most of the problems happen when the Storm water does not enter the drains, or the drains are blocked or have a reduced capacity due to debries and other foreign bodies.

3)If You want to do a reasonable urban watershed analysis, you usually need a DSM/DTM with accuracy of a few cm, which is possible only from something like a LIDAR survey, and not from Satellite Data.

Regards,

Devdatta

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[Dilip Damle]

HI, 

I do not know your project nor whom you are working for. 

However I have worked professionally as a consultant On Many Water Supply, a few Sewerage projects and to a lesser extent on Stormwater projects. I also had my own water supply network software (before commercial software were easily available)  with which I have done network planning for many large projects in different parts of the country.

With that background I would say For a large city these kinds of projects involve a large PAID team with expertise in their own areas. Say my area was design and Hydraulics analysis but I can not work without another member without a GOOD site experience. So trying to look at these things just a s a software problems and getting help online may not really work.

The most important part to start with is a real land survey to get actual ground levels. There is no way they can be estimated from anywhere.
Unfortunately newer people do not understand the complexity of the issues. Also we try to fudge everywhere including survey. 

Your exercise will also involve analyzing the entire network existing and proposed.

So any help from someone other than without a domain experience and  responsibility against payment will be much less than a milligram of lipstick.

If you think you can put together things from here and there, you cannot. If you could then you would not have asked here. 



Availabee Digital elevation model is useless (inadequate) for this project.

Knowing Bangalore as the city where I will shift in near future and I live there (ALSO). I would say the following specifically about the city. 

Since it is highly undulated city there are advantages that you will get a good gravity assist in the network. But at the same time you will have many points from which sewage will have to be collected and pumped to the STP. This complexity and planning is HUGE.

I just hope (for the sake of the city) that nonone is working with a shoestring budget on this one. Or the shoestrings are controlled by some other strings.

Apologies for being forthright and clear on the issue.

[Dilip Damle]

I would add that if anyone anywhere is even thinking of interpolating ground levels then it is the biggest Blunder that can be done. Unfortunately these days of software we have distanced ourselves from ground realities and fundamentals and even such ideas are offered as innovation/smartness and sold to ignorant management. 

[Sharad Lele]

@Nagesh: I strongly endorse Dilip's warning. And I would add another question: One needs to be clear what one is trying to find out (question comes before tool) and whether the answer is already approximately known before hitting it with a tool that has all the limitations Dilip mentions. So what is the question?

For instance, we already know that the installed STPs don't operate at full capacity and that the problem is largely to do with clogged UGDs, broken UGDs and incomplete UGDs. E.g., Vrishabhavathy Valley STP has installed capacity of 180 MLD. One of the units does not work, so effectively 120 MLD. But even this 120 MLD consists of only 20-25 MLD of raw sewage coming from the UGD, rest is diluted sewage being picked up from the river. We have a published paper on V-Valley STP (mal)functioning.

We also know that even as K&C valley STP capacity is being upgraded, it gets some of its sewage (60MLD) by pumping from the Agara side and will get another 100 MLD pumped from Ejipura drain (pickup point several km before drain reaches Bellandur).

So any simple terrain-based analysis is pointless when on the one hand gravity-based movement is blocked by clogged UGDs and on the other hand pumping moves sewage around.

Sharad

[Nagesh Aras]

Dear all,

I am clear from the start that-
(a) we have daunting limitations,
(b) we need to have local survey data and
(c) we may need to pay for some of the expertise.

But the recent lake rejuvenation program has thrown up possibility to approach this in a proper way.
I am collecting ideas in that context.

The original recommendations of the expert committee are posted here.
But there is no progress in any of the items.
Now there is a possibility that this program will be driven by activists.

And those activists should have proper guidance from experts.

Can we request the expert committee members to hold a workshop to debate all options and develop a solution publicly?

[Dilip Damle]

Hi,
Thanks for the document. I have just browsed through it.

I get some hint of the enormity of the task   looking at the document.

I am not a domain expert in the Lakes / Waterbodies / Storm water management.

But having worked  as part of /with teams on environmental projects mainly in Computer /Software / CAD part this is what I feel.

 The objective /task (whatever it is ) at hand need some people with a proven past domain expertise in that area who have done similar large (HUGE) projects.

I think some expert  from Central water Commission or some such large organisation only will be able to even asses the real enormity of the task. 

I do not know if any Activists (do not know what that would mean exactly)  will be able to see the large picture.

I read that @Sharad Lele was also a part of the committee so he will know much better.

[harsh dave]

Hi Nageshji,

I am new to Arcgis still learning, if still needed i can help.