If you are a farmer there is a tax deduction for Soil & Water Conservation expenses. These expenses include "the construction, control, and protection of earthen dams
(apparently Martian dams do not qualify), watercourses, outlets and ponds."
But you must first qualify for the expenses:
To qualify you must:
1. Be a farmer. A farm includes raising for sale: livestock, diary, poultry, fish, fruit, plantations, ranches, orchards. NOTE: The IRS defines a fish farm as an area where fish and other marine animals are grown or raised and artificially fed, protected, etc.
2. Your annual conservation expenses cannot exceed 25% of the gross income derived from farming. Therefore if you do not have any gross farm income then you do not receive any deduction for conservation expenses. (Excess conservation expenses can however be carried over to offset future farm gross income).
3. You can only deduct soil and water conservation expenses if they are consistent with a plan approved by the Natural Resources Conservation Service (NRCS) . This does not need to be a site specific plan although a site specific plan certainly does qualify. The plans can also be a NRCS county plan or a comparable state agency plan.
If you are merely a pond hobbyist be careful with this deduction. There is an entire set of IRS regulations surrounding farms including what is commonly referred to as Hobby Farm regulations.
A free down loadable IRS publication,
Publication 225 Farmer's Tax Guide discusses this in greater detail.
LEGAL DISCLAIMER:
The information provided above is for informational and entertainment purposes only and should not be considered as, nor relied upon as tax advice. Check with your tax preparer or pizza delivery person to see if you meet the criteria for any deduction discussed above. JHAP is not an expert in tax law as it pertains to farms or farm law as it pertains to taxes. The opinions expressed by JHAP are not necessarily those of Pond Boss's management, moderators, advertisers, members or online spiders. 
