Groundwater is water beneath Earth's surface in rock and soil pore spaces. About 30% of world's fresh water is groundwater. Aquifers are underground layers of water-bearing materials. Water table is depth where soil pores become completely saturated
Rome's first aqueduct was built in 312 BC to supply the city's cattle market. Aqueducts moved water through gravity along steep gradients using various materials. Conduits were buried underground and followed terrain contours. Systems included sedimentation tanks and distribution tanks for water management
Las Vegas is Nevada's most populous city and Clark County's seat. Population reached 641,903 in 2020, with 2,227,053 in metropolitan area. Known as "Entertainment Capital of the World" and "Gambling Capital". Hosts over 40.8 million visitors annually
Singapore is a city-state located between Malaysia and Indonesia. Mainland measures 50 km east-west and 27 km north-south. Diamond-shaped island with 193 km coastline. Highest point is Bukit Timah Hill at 165 m. Most of island is below 15 meters above sea level
Australia's longest river at 2,508 km, forming Murray-Darling basin. Originates in Australian Alps, flows northwest across inland plains. Forms border between New South Wales and Victoria. Empties into Great Australian Bight through Murray Mouth
Two parallel rivers flow through Middle East, originating in eastern Turkey. Euphrates is 1,740 miles long, Tigris 1,180 miles long. Rivers diverge sharply in upper courses, reaching maximum 250 miles apart. Form Shatt al-Arab at Al-Qurnah, emptying into Persian Gulf