How to add ponds & lakes ?

[Hydro Water]

Hello users,

I have rather a simple question. I have number of lakes, ponds and wetlands in my study area. Right now i can see only the option of adding reservoir (watershed delineation features). I have looked into different menus but couldn't come across with adding ponds or lakes option. Can some please direct me to those options?

Regards,

Ameer

[Jim Almendinger]

I add Ponds and/or Wetlands simply by directly modifying the pnd table in the project database. I'm not sure how you enter the data via the interface (probably obvious -- I'm not at my computer). Usually I just make a table in Excel with the relevant data, upload it to the project database, join it to the pnd table (by subbasin number) and then use an update query to populate the pnd table with the Pond or Wetland data (areas and volumes).

In case it's not obvious, SWAT allows only one Pond and one Wetland per subbasin. The most straightforward way is to just add up all the areas and volumes of all the ponds in your subbasin and just lump them together as a single pond. However -- clearly individual ponds treat runoff differently then a single large pond, and the "best" way to aggregate many small ponds into a single large pond per subbasin is an area that should be researched.

A critical field is the pnd_fr and wet_fr variables, which tell SWAT how much of the water yield of each subbasin is intercepted by the impoundment. Once you enter all the Pond table, you can easily "turn off" Ponds by setting pnd_fr to zero, or "turn on" Ponds by setting pnd_fr back to your selected value. Again, I do this with update queries in the project database, operating directly on the pnd table. I turn off Ponds (set pnd_fr = 0) when I want to see the direct, unmodified output from HRUs. Otherwise, the HRU output gives you the HRU yields after the HRU water yield has been "treated" by the Pond (or Wetland).

Cheers,
-- Jim

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--
Dr. James E. Almendinger
St. Croix Watershed Research Station
Science Museum of Minnesota
16910 152nd St N
Marine on St. Croix, MN 55047
tel: 651-433-5953 ext 19

[Hydro Water]

Hi Jim,

What a nice explanation (Many thanks). My study area is Upper Assiniboine River Basin (Manitoba-Saskatchewan) where I have a large number of potholes, wetlands and ponds. I split my area in 9 sub basin defining an outlet in such a way that all major lakes/ponds fall one in each basin. For the potholes, i guess i will sum it up based on your suggestion for each sub basin. I see that a large number of inputs are required to populate the Pnd database, i guess the most important one would be the surface area, volume, K and likewise detail for wetlands. i will leave the rest as it is. One confusing term was the principal and emergency spillway term (i believe this would mean the normal and maximum level??). my ponds/lakes are non regulated and natural so i would take it as area and volume at normal and maximum level. Not sure, if there are other important information that shall go into the pond (Pnd) database

Many thanks again,

Ameer

Ph.D Candidate
University of Manitoba

[Hydro Water]

Hi Jim,

Can we say (guess)  PND_FR = (PND_PSA / Total area of sub-basin). Is there any way to compute PND_FR?

Regards,

Ameer

On Thursday, December 31, 2015 at 3:21:34 PM UTC-6, Jim Almendinger wrote:

[Jim Almendinger]

Ameer --

Yes, you will have to estimate many parameters about Ponds (and/or Wetlands), for which there will likely not be much real data.  The areas you can get from land-cover data (satellite or aerial photos), or open-water GIS data for your watershed, if you're lucky.  You'll likely have to guess about average water depths (I often use 1.5 m for small water bodies with no data).  This would give you principal areas and volumes. 

"Emergency" areas and volumes are somewhat conceptual.  In the model, all flow above an emergency volume is spilled downstream during the same time increment it occurs.  I.e., there is no available storage to reduce stormflows above the emergency volume.  This doesn't really happen in reality, but it keeps the model from flooding large parts of subbasins (which might actually occur).  I don't have good advice here -- I usually pick some multiple of the principal area (2-3x?) and principal volume (3-5x?) to estimate the emergency area and volume. 

"Natural" drawdown of the Pond levels occurs at the rate determined by NDTARG, and only for water volumes above principal and below emergency -- and only for the designated "flood" months.  During "non-flood" months, the water level is allowed to rise up to the emergency volume, below which nothing spills and above which everything spills.  This is unrealistic, so I avoid using "non-flood" months as much as possible.  The parameters IFLOD1 & 2 are used to set the beginning and end of the non-flood period -- which I don't want -- so I set IFLOD1=12 (December) and IFLOD2=1 (January).  This minimizes the "non-flood" season to be just from December to January, but that's OK in my part of the world where little is flowing in the winter (the same would be true enough for most of Canada). 

Finally, setting PND_FR (or WET_FR) is even more a guessing game at this point.  A simple approximation could be to assume it's a simple multiple of the principal area.  In one of my watersheds, where I did more work with the DEM to try and actually measure it, the PND_FR value was about 3.3x the principal area (with the entire subbasin area as the upper limit, which is very possible in some settings).  BUT -- this is highly variable and could be off by very large amount.  Next year I hope to have a student or colleague help construct a GIS tool that will calculate cumulative depression area, volume, and drainage area in a subbasin, which could then objectively be used to parameterize SWAT.  Until that time -- and with no promises -- you'll have to estimate on your own as objectively as possible. 

I usually start out with the K value = 0 to stop all seepage, and only increase it as needed.  If you have a non-contributing basin (i.e., no surface outlet), you can increase K (to 5-10?  I forget...) to be large enough so that the Pond always seeps out and never spills, thereby trapping all sediment (and all phosphorus?). 

Wetlands function identically as Ponds, except that the NDTARG value is hard-coded to be 10 days.  This may not be appropriate, so lately I've just been using Ponds.  Or, in some cases, I've used Wetlands to represent closed depressions (high seepage, no spilling) and Ponds to represent open depressions (spilling to a surface-water outlet), since they (should) impact water quality very differently. 

The good thing about Ponds is that you can alter the parameters easily.  The bad things -- well, they never quite seem to have the hydraulic and water-quality impacts that I expect.  The whole flood vs. non-flood month stuff should be simplified and removed in the default case, so all volumes between principal and emergency flow out based on NDTARG or an input stage-discharge relation.  Seepage must be allowed to contribute to baseflow (if it doesn't already). 

Remember -- when you add Ponds, they will alter your HRU-level output.  To see the "raw" HRU water, sediment, & nutrient yields before they are altered by draining into Ponds, turn off Ponds by temporarily setting PND_FR=0 for all subbasins. 

That should get you started,

-- Jim

---

From: "Hydro Water" <hydro.wat...@gmail.com>
To: "ArcSWAT" <arc...@googlegroups.com>

Cc: "hydro water climate" <hydro.wat...@gmail.com>
Sent: Friday, January 1, 2016 12:33:01 PM
Subject: Re: [ArcSWAT:7810] How to add ponds & lakes ?

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[Ramabrahmam K]

Hi jim.

Thanks for your detailed information, i  have gone through the all detailed information you have given. but i have some question regarding Ponds in QSWAT.

1) I have taken PND_FR=1, on the basis of, sub basin delineated  by taking pnd as outflow, so total  sub basin drain to pond only. is it correct?(bcz i dont have any field observations).

2) I had added pond as per the subbasin wise and simulated by taking nearby observed river discharge data, but i didn't found any pond related table in SWAT input and output dbm files. i need the vol of water in tank at the end of the day. how can i get this?

3) My study area of  pond are inter connected (cascade), tanks also having the sluices to release the water for irrigation. how can i add the release for he pond?

4) I had given the pnd K =0.7 to 0.9. is itcorrect ?

kindly give response. 

Thanking you.

Regrads

K.Ramabrahma

NIT Warangal, India.

On Wednesday, January 6, 2016 at 1:44:43 AM UTC+5:30, Jim Almendinger wrote:

Ameer --

Yes, you will have to estimate many parameters about Ponds (and/or Wetlands), for which there will likely not be much real data.  The areas you can get from land-cover data (satellite or aerial photos), or open-water GIS data for your watershed, if you're lucky.  You'll likely have to guess about average water depths (I often use 1.5 m for small water bodies with no data).  This would give you principal areas and volumes. 

"Emergency" areas and volumes are somewhat conceptual.  In the model, all flow above an emergency volume is spilled downstream during the same time increment it occurs.  I.e., there is no available storage to reduce stormflows above the emergency volume.  This doesn't really happen in reality, but it keeps the model from flooding large parts of subbasins (which might actually occur).  I don't have good advice here -- I usually pick some multiple of the principal area (2-3x?) and principal volume (3-5x?) to estimate the emergency area and volume. 

"Natural" drawdown of the Pond levels occurs at the rate determined by NDTARG, and only for water volumes above principal and below emergency -- and only for the designated "flood" months.  During "non-flood" months, the water level is allowed to rise up to the emergency volume, below which nothing spills and above which everything spills.  This is unrealistic, so I avoid using "non-flood" months as much as possible.  The parameters IFLOD1 & 2 are used to set the beginning and end of the non-flood period -- which I don't want -- so I set IFLOD1=12 (December) and IFLOD2=1 (January).  This minimizes the "non-flood" season to be just from December to January, but that's OK in my part of the world where little is flowing in the winter (the same would be true enough for most of Canada). 

Finally, setting PND_FR (or WET_FR) is even more a guessing game at this point.  A simple approximation could be to assume it's a simple multiple of the principal area.  In one of my watersheds, where I did more work with the DEM to try and actually measure it, the PND_FR value was about 3.3x the principal area (with the entire subbasin area as the upper limit, which is very possible in some settings).  BUT -- this is highly variable and could be off by very large amount.  Next year I hope to have a student or colleague help construct a GIS tool that will calculate cumulative depression area, volume, and drainage area in a subbasin, which could then objectively be used to parameterize SWAT.  Until that time -- and with no promises -- you'll have to estimate on your own as objectively as possible. 

I usually start out with the K value = 0 to stop all seepage, and only increase it as needed.  If you have a non-contributing basin (i.e., no surface outlet), you can increase K (to 5-10?  I forget...) to be large enough so that the Pond always seeps out and never spills, thereby trapping all sediment (and all phosphorus?). 

Wetlands function identically as Ponds, except that the NDTARG value is hard-coded to be 10 days.  This may not be appropriate, so lately I've just been using Ponds.  Or, in some cases, I've used Wetlands to represent closed depressions (high seepage, no spilling) and Ponds to represent open depressions (spilling to a surface-water outlet), since they (should) impact water quality very differently. 

The good thing about Ponds is that you can alter the parameters easily.  The bad things -- well, they never quite seem to have the hydraulic and water-quality impacts that I expect.  The whole flood vs. non-flood month stuff should be simplified and removed in the default case, so all volumes between principal and emergency flow out based on NDTARG or an input stage-discharge relation.  Seepage must be allowed to contribute to baseflow (if it doesn't already). 

Remember -- when you add Ponds, they will alter your HRU-level output.  To see the "raw" HRU water, sediment, & nutrient yields before they are altered by draining into Ponds, turn off Ponds by temporarily setting PND_FR=0 for all subbasins. 

That should get you started,

-- Jim

---

From: "Hydro Water" <hydro.wa...@gmail.com>
To: "ArcSWAT" <arc...@googlegroups.com>
Cc: "hydro water climate" <hydro.wa...@gmail.com>

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[rambr...@student.nitw.ac.in]

[Bhaswatee Baishya]

Hello Jim,

Thank you for explaining it so clearly. But in the first mail, you mentioned preparing the data in excel, whether you have prepared it manually or have used any tool. How you got the information of all the columns as presented in the project database pnd tab? Also, during automatic delineation, do we have to add these pond locations in the add reservoir part ?? when to change the project database (pnd tab)??

Regard

[Filipe Pinhati]

Hi Jim, this was a great explanation, thank you so so much.

Dear  Bhaswatee Baishya, based on Jim's explanation, all you have to do is:

0. create backups of your project/database

1. copy the '.pnd' table from your ArcSwat/QSwat database (*.mdb)

2. paste it in Excel.

3. edit the columns you want to edit

4. paste it back into the '.pnd' table in your database

5.1 rewrite the modified files in ArcSWAT/QSwat, or

5.2 rewrite each pond manually on each '.pnd' file in your 'TxInOut' folder.

Regards

Phil

(Filipe Pinhati)