I have recently moved into this home with a Gardena WT 1030 watering system. I have no manual and need activate the timer. How does it work? Can I download a manual?

I cannot find T1030D manual posted anywhere, Aug 2011.
The Gardena site does not return emails or post manuals.
You can try the following 'possible instructions' and then add a comment saying what you discover.
http://waterheatertimer.org/pdf/Instructions-for-setting-Gardena-T1030D.pdf
http://waterheatertimer.org/How-to-program-Gardena-C1060.html#manuals

There are different 1030 gardena timers, and some gardena products have 3 different numbers, and sometime different timers have identical number.
Some Gardena manuals appear on following link with images of different products:
http://waterheatertimer.org/How-to-program-Gardena-C1060.html#manuals

I do not have image of internal parts.

Open following link for Gardena resources, including contact information for Gardena:
http://waterheatertimer.org/How-to-program-Gardena-C1060.html

Some Gardena manuals appear on following link, and additional manuals are posted as found:
http://waterheatertimer.org/How-to-program-Gardena-C1060.html#manuals

Also Google search "Gardena C1030 .pdf" or "Gardena C-1030 .pdf"
Be sure and add .pdf to search parameter to help isolate manuals from other internet posts
Gardena for some reason does not have manuals easily available as of today's date.

Add a comment for more free help

Also take advantage of fixya expert assistance live.
For a price, expert works with you while you work on timer or any do-it-yourself project.
Fixya is always less expensive than a service call.

1) I might have that manual in English:
http://waterheatertimer.org/pdf/Gardena-T1030.pdf
http://waterheatertimer.org/pdf/Gardena-T1030-MANUAL.pdf

2) If manual above doesn't work, I also used Google translate to translate Gardena manual; from Italian and German if I recall:
http://waterheatertimer.org/How-to-program-Gardena-C1060.html

You can enter whole sentences into google translate, and make sense of 70-80%.
I sometimes answer questions in Spanish at fixya using the translator. So we're not helpless any more.

3) Add a comment for more free help.
Also take advantage of fixya phone service.
For a price, fixya expert speaks with you over phone while you work on timer.

I have Gardena 1030 manual
http://waterheatertimer.org/pdf/Gardena-1030-MANUAL.pdf

Add a comment for more free help.
Also take advantage of fixya phone service.
For a price, fixya expert speaks with you over phone while you work on timer.

Some Gardena manuals appear on following link:
http://waterheatertimer.org/How-to-program-Gardena-C1060.html

http://waterheatertimer.org/pdf/Gardena-1030-MANUAL.pdf

The manual above has several languages, including English

http://waterheatertimer.org/Gardena-1030-MANUAL.pdf

Gardena T1030 manual

most likely the battery needs changing...