Here are two articles on the positive effects of melon juice as an alternative for citrus juices especially for those with intense GERD.
Noncitrus Alkaline Fruit: A Dietary Alternative for the Treatment of Hypocitraturic Stone Formers.
Food Chem Toxicol. 2011 Sep;49(9):2433-8. Epub 2011 Jun 28.
Protective effect of Diyarbakır watermelon juice on carbon tetrachloride-induced toxicity in rats.
J Endourol. 2012 Jun 4. [Epub ahead of print]