Donate 1,000 Imperial Bronze Pieces to Gajaad at (J-6) in Al Zahbi in support of the city's defenses. Trade him 100 Imperial Bronze Pieces at a time and for every trade with 100 or more, he will give you a Walahra Water. When a total of 1,000 Imperial Bronze Pieces are traded, he will give you the Walahra Turban.
If Gajaad says: "I hear that Chochoroon the appraiser has been taken by the beastmen... Oh my...! If he should be forced to talk, then they might come looking for me next time!", he will not accept your trades. You will have to wait until Chochoroon is returned.
You may trade as many coins as you like to Gajaad at a time. He will accurately keep track of the number, regardless of how many you stack into the trade window. However, if you want Walahra Water as a reward, do not trade more than 100 at a time – he will only give you one water per trade, regardless of how many additional coins you trade (i.e. 700 coins would only result in 1 water, not 7).