0.1 Background
Introduce the area
History
ography & Climate - https://www.weather.gov/vef/ClimateofLasVegas - Aquifer system (geology, flow, add an image of a cross section if one is available)
- Geology
- [[galloway-et-al-1999]]
- Las Vegas Valley is bounded on the west by several mountain ranges and drains a 1.564-square-mile watershed southeastward through Las Vegas Wash into Lake Mead
- Las Vegas Valley is a sediment-filled structural trough that has formed over many millions of years through compression, extension, and faulting of the original flat-lying marine sediments that form the bedrock. Sediment eroded by wind and water from the surrounding bedrock highlands began filling the trough with gravel, sand, silt and clay.
- During some of the wetter periods in the past 1 million years or so, extensive playa lakes and spring-fed marshes covered the lower parts of the valley floor, depositing variably thick sequences of fine-grained sediment (Mifflin and Wheat, 1979 and Quade et al.,1995). Coarse-grained sand and gravel tend to rim the valley, forming alluvial fans and terraces, especially in the northern, western , and southern parts.The deposits generally thicken and become finer- textured toward the central and eastern part of the valley, where their total thickness exceeds 5,000 feet (Plume, 1989) .
- [[galloway-et-al-1999]]
- Groundwater Flow
- [[galloway-et-al-1999]]
- Groundwater is generally pumped from the upper 2,000 feet of unconsolidated sediments that constitute the aquifer system in the central part of the valley. The deeper aquifers, generally below 300 feet, are capable of transmitting significant quantities of groundwater, and have been referred to variously as the principle aquifers. In places, these principle aquifers are more than 1,000 feet thick and consist mainly of sands and gravels beneath the terraces along the margins of the valley. In the central and eastern parts, clays and silts predominate ( Plume, 1989).
- Overlying the principal aquifers , in most places, is a 100- to - 300 foot-thick section ofextensive clay, sand, and gravel deposits known as the”near-surface reservoir.” The principal aquifers and the near- surface reservoir are separated by a variably- thick, laterally discontinuous aquitard, or confining unit.
- Much of the ground water found in the aquifer system originates as rain or snow falling on the Spring Mountains to the west or on the Sheep and Las Vegas Ranges to the northwest. Some of the precipitation infiltrates into the underlying bedrock through faults and fractures, eventually moving into the deposits comprising the principal aquifers. The remainder of the precipitation runs off onto the sloping alluvial terraces and rapidly enters the sand and gravel deposits, where it either recharges the underlying principal aquifers or is evaporated or transpired into the atmosphere.
- 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. The increasing proportion of fine-grained deposits retards lateral flow, and the low- permeability deposits effectively impede the vertical flow of ground water. As ground water recharges the aquifer system from the higher elevations, fluid pressures in the principal aquifers can buildto create artesian conditions at lower elevations in the basin.
- [[galloway-et-al-1999]]
- Geology
- Land uses and climate conditions
- Groundwater demand
- Las Vegas Valley was the fastest growing metropolitan area in the US circa 1999 and the accelerated demand for water was being met with imported water from the Colorado river and local groundwater, which lead to the depletion of one-plentiful groundwater supplies, land subsidence (around 6ft) and ground failures.
- Aquifer system (geology, flow, add an image of a cross section if one is available)
At the time, the current water supplies were expected not to satisfy the anticipated water demand with the federally mandated limit placed on imported water. supplied from Lake Mead, likely to force a continued reliance on ground water.
- Groundwater level changes
- Include plot of groundwater level changes over time ### Intervention
- Groundwater level changes
Describe the intervention(s) that took place,
Introduce key concepts and, if relevant, locations of projects within the study area
Examples of interventions may be managed aquifer recharge projects, new policies, changes to groundwater market conditions, development of an alternate water source
Where possible, be quantitative (e.g., if groundwater pumping declined, show a graph highlighting the change in pumping over time) ### Outcomes
Describe the consequences (good and/or bad) of the intervention
Show a plot of groundwater level changes over time, and mark the year(s) that the intervention took place ### Summary
Summarize your main findings.
State the one big take away from your work (i.e., if there was just one thing your audience should learn from your work, what is it)
1 Script
- Las Vegas initially contained several artisan wells supporting extensive green areas (hence the same where ‘vegas’ is spanish for ‘meadows’).