Imagine an eco-conscious city where rooftops have been transformed into fertile, green gardens. It's a place where every home is equipped with a system that recycles valuable water resources. In this town, protecting the planet is a way of life. That's how Abby Sharp, 14, Wyatt Peery, 13, and Tom Krajnak, 14, saw their city of tomorrow. The vision won the eighth-graders from Bexley, Ohio, first prize at the 2009 National Engineers Week Future City Competition. The annual design competition challenges middle school students to use engineering to deal with issues that affect the earth. This year the competition focused on water conservation. Participants had to come up with ways to improve water use in the home. Kids from 38 middle schools across the country competed in the finals. The event took place from February 17-18 in Washington, D.C. More than 30,000 students entered the competition. Abby, Wyatt and Tom call their winning city Novo Mondum. The name means "new world" in Latin. Novo Mondum sits on the coast of Iceland. The group chose the spot for its wealth of clean energy resources, such as geothermal  energy and hydropower. Both sources use the power of nature to generate electricity. Geothermal energy draws heat from deep inside the Earth. Hydropower gets energy from flowing water. "Our city is very globally aware," Abby told TFK. Students team up with a teacher and a volunteer engineer mentor to develop their cities. Each group creates a fictional city on SimCity 4 Deluxe, a computer game that allows players to build virtual towns. Then they construct tabletop models of the cities and write essays describing their project. The models must be made using recycled materials and cost no more than $100 to build. It can be inferred that water conversation is   _  .
one of the problems that influence the Earth. the main theme of 2009 Future City Competition. one of the issues for the participants to deal with abroad. an easy topic for all the students to design.