I don't think the subsurface irrigation is a solution to deepening water level. The most optimized irrigation is the drip irrigation in this case of trees and sprinkler in case of other crops. 

Hi Bita, by using sap flow sensors you can potentially determine how different irrigation practices are affecting your trees and their roots. In a literature search look for keywords such as hydraulic redistribution and authors such as Jan Cermak and Nadezhda Nadezhdina who have many publications on this topic (I have attached a couple of papers for you). If you do use a sap flow sensor make sure it is one that can measure both positive, low and reverse flow: http://www.ictinternational.com/casestudies/instrumentation-for-total-tree-water-use-and-behaviour

http://www.ictinternational.com/casestudies/instrumentation-for-total-tree-water-use-and-behaviour

Article Transpiration in Quercus suber trees under shallow water tab...

Chapter Root Function: In Situ Studies Through Sap Flow Research

Hello Bita,

In general, root systems are dynamic and they are continuously adapting to explore soil resources, although root systems have species specificity. Old trees, maybe, have less capacity to adaptation to new water regime. 

Sometimes depending on tree species, the conventional irrigation represents a loss of water due to water goes too deep, out of the tree root system. However, in dry climates, tree root systems can grow deeply, and therefore they have more soil volume to explore for water and minerals. Assuming that in your area there are also significant rainfall to load the soil profile, it is reasonable accept that your trees root systems will have a soft transition to their soil volume availability. Anyway, keep in mind that your new irrigation schedule should be set up in terms of water balance.

Dear Saif Uddin

Thank u so much for your answer, i mean subsurface drip irrigation, The plane trees are more than 100 years old. The problem is we dont know where  the roots are. Did you see the similar cases irrigated with drip irrigation with out any problem?

Thank u so much. 

Dear Michael., 

Thank u very much for the articles, Let me read them and ask you my questions please. 

Again thank u so much.

Bita

Dear Antoni

Thank u so much, I agree with u. 

The plane trees are more than 100 years old, i want know what the depth i should distribute water to sure the root system adapted to this new  condition? 

Thanks a lot for your benefit explanations

Tthe root system is highly adaptable, for a 100 year old trees certainly they must have a bery intricate root system and drip irrigation can easily help them irrigate with quite a less quantity.

According to our view  new system of irrigation will be effective for the areas where water table is very low. It save water quality and quantity both. As Root hairs of Tap root absorb applied surface water and supply whole the plant parts effectively

Dear Mr Saif Uddin

So if i agree with u, the question is where the roots (depth) are? In which depth i should install dripline? (Remember that the trees are more than 100 years old)

Thank u so much

Dear Anil Kumar Mishra

Could you please send me the articles or researches about that?

Thank u so much

Bita,

Planetrees are naturally associated with riverbanks but can even survive well rather dry conditions (ie. urban)

if I do understand well : the ground-water table has been lowered from -30 to -60 meter below ground level ?  I am affraid no tree can profit from water at this level (even the -30 meter); except some specialists in desert & arid conditions..  So the trees depend on the rainfal etc. for their water-use (helped by the soil-water-retention). Or there must be some underground streams ? Can you see specific drough damage symptoms to the trees / stand and which ones ? >> water balance (in-/output)...  

A practical soil-survey (incl. soil- & rootprofile) will give you lots of accurate information. When installing an irrigation : the trees will become dependent on the system (which is not a structural advantage) (of course, this depends on options, policy, natural or urban/cultural conditions,...). 

You can stop over-evaporation (and higher the water-retention) of the soil by ammending well-degraded compost on top of the soil.

might there be to much competition  between vegetation ?

The dryer the soil-conditions are the more soil-volume trees will explore.  Any idea on the average evapotranspiration-levels ?

If you have trees that should cut : look for the dendrochronological profiles(to look how the stand did react to the dryer conditions).

Dear Arthur 

Thank you so much for your very good answer. 

We think that this traditional irrigation method we use these days, never supply the water need of these trees. Yes we think these trees supply their water need from another underground streams.

Most of the trees  are Buttonwood planted  many years ago in different condition compared to now.

These trees are usually in landscape (Single plant species). In some cases these trees are planted with shrubs.

Yes, most of the trees shown drought damage symptoms like dry tree branches or broken trees because of drought. 

So what could we do for that?

We must change the irrigation method. Water could not reach to deep soil layer using drip irrigation, this traditional method of irrigation is not efficient. Maybe the only way is subsurface irrigation. What do you think?

Many Thanks.

Best Regards

Bita

Bita,

Buttonwood is native in the US; can't it be the Platanus orientalis which is native in your area. 

Sorry for my doubt but so far I am not realy convinced about the origin of the problem.

Can you please send some pictures (general view of the area, map, location or areal view, specific symptoms  of drough damage (i.e. necrosis of leafmargins (!), branch dying starting from the branchtop,..).

Can't you see big wood-cankers on the stems, branches ?  There might be a risk that the disease Ceratosistys platani is involved which can initiate tree-decline and give the impression of drough damage.  the disease has already been reported in Iran (http://webarchive.nationalarchives.gov.uk/20140904082245/http://www.fera.defra.gov.uk/plants/plantHealth/pestsDiseases/documents/planeCanker.pdf)

Bita,

I forgot to write that there are more pathological reasons for tree decline i.c. Apiognomonia erabunda.  for instance a leaf-fungus but if the pathogen occurs early and heavely twigdeath and even (smaller) branchdeath may be a(n atypical) symptom.  and in that case the trees may become more sucsesible to other (secondary) diseases.

Apiognomonia is favorised by colder springseasons.

I look forward for seeing the pictures.

best regards

Arthur

Dear Arthur

Thank you so much for your kindly helps. I think the resone of tree branches drought is not disease, some research project have done in this case. 

But may be you are right, i will send you the photos you want as soon as possible. 

Could you please tell me your email address?

Again thank you so much. 

Best regards

Sorry Bita,

[email protected]

I do work for the www.inbo.be  where I do deliver tree-diagnose-services (solving tree- / forestprobroblems caused by (a-)biotic factors).

regards,

Arthur

Dear Arthur

Thank you so much

I will send you the photos as soon as possible. 

Best regards