Part III of III: Our series concludes on San Diego's long-range challenges with infrastructure. This month, we examine the issues relating to water (is the glass half-full or half-empty?). And power (it's a commodity in low supply and growing demand). Also, we see where things stand on the most widely studied problem that's never come to resolution: a site for a new airport. Finally, Neil Morgan writes about San Diego and philanthropy --will new money help solve some of our infrastructure woes?