What are the types of sediment that fill the Valley? Gravel, sand, silt, and clay How does the porosity and permeability of these materials determine the location of groundwater and it rising the surface? Coarse-grained sand and gravel tend to rim the valley forming alluvial fans and terraces. There thickness and grain size. Groundwater Flows through the Aquifers How deep are the Aquifers? Below 300 feet. Where are they located? The sheep and Las vegas ranges to the west. Describe the types of sediment found in each. Extensive clay, gravel, and sand. Where does the groundwater in the Valley originate? As rain or snow. Describe the movement of the water in the basin. Near the margins of the valley, ground water moves freely through the coarse-grained sand and gravel deposits, but as it moves basinward it begins to encounter increasingly greater percentages of lower permeability, fine-grained clay and silt. How did the artesian wells effect the Valley? Forced water slowly upward through confining zones and more rapidly along faults. The Changing Balance between Recharge and Discharge What are the effects on the natural hydrologic cycle since groundwater has been taken out in such vast amounts? More water going out than in. Desscribe Las Vegas' water budget before and after groundwater withdrawal. The present water budget reveals that only a small fraction of the water used in Las Vegas Valley is actually con- sumed, and therefore removed from the water cycle, by domestic agricultural and municipal/industrial uses.