. >> reporter: tom rankin is a professor of urbanism at rome's la sapienza university. >> the romans were smart. they started removing the groundwater where it was undesired, using it for their water source, wells. >> reporter: the ancient romans were master engineers of water. >> they really were. the sewer system was certainly in place in the 4th century b.c. and it's still functioning today. it's probably the most cost- effective public works project ever built. >> reporter: but modern city planning has fallen short. the drought is one thing, he says. but long-term mismanagement is also to blame. officials from both the city and the water utility declined requests for an interview. >> rome, of all the european capitals, is the only city that has a fully sustainable water supply. meaning that the water table is recharged faster than the city can use the water. the real problem isn't that it can't provide for the population, it's the waste of water. the water system is damaged. at least 25%, some say up to half of it leaks out before getting to its destination. >> reporter: leaks li