* Rising heat and drought reducing water for Nile Delta farmers * Filling of upstream Ethiopian hydropower dam also seen as a risk * Analysts warn Mideast water scarcity could harm social stability By Menna Farouk EL-SHAWASHNA, Egypt, Oct 31 (Thomson Reuters Foundation) - F or three decades, brothers Ramadan and Mamdouh Othman have grown summer crops of maize, olives and cucumbers on their Nile Delta land in Egypt's northern governate of Fayoum. But over the past year, the amount of water in the canal that supplies their sandy 3-acre (1.2-hectare) farm in the village of El-Shawashna ha...