Aquifers in Alluvial Sediment • River valley draining glaciated area • Rivers draining area in west with high Pleistocene rainfall • Fault-bounded basins in west • Partially dissected alluvial plain (High Plains) Unconsolidated sands and gravels deposited by rivers. Must be large enough to produce significant rates and volumes of water (b>5 to 10m)
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Aquifers in Alluvial Sediment River valley draining glaciated area Rivers draining area in west with high Pleistocene rainfall Fault-bounded basins in.
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Aquifers in Alluvial Sediment
• River valley draining glaciated area
• Rivers draining area in west with high Pleistocene rainfall
Unconsolidated sands and gravels deposited by rivers. Must be large enough to produce significant rates and volumes of water
(b>5 to 10m)
Sea vs. Closed Basin as Deposition Site for Alluvial Sediments
Sea• Suspended load
possibly removed
• Salts possibly removed
• Sea level change important
Closed Basin
•Fine-grained seds in system
•Salts remain
•Isolated from effects of sea level change
•Affected by local climate
Alluvial aquifers in glacial deposits
Alluvial sediments in glaciated areas
• Glaciers advance, scour seds., modify river course. Sed comp. depends on location/source material. Large range of grn size. Till=clay-boulder beneath glacier.
• Glaciers recede. Discharge increases. Erosion. Braided rivers, large sediment capacity. Outwash plain (sands and gravels). Lakes in front of receding glaciers. Lacustrine=clay-silt (varved)
Dissolution of underlying evaporites forms deep troughs in Pecos River Basin
80 Mgpd
Water Quality: 1000+ mg/L common due to underlying evaporites and recharge from saline surface water and irrigation return flow where evaporation has increased salt content