GEOL201 Hydrology - Groundwater PDF

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Summary

Osman Salad Hersi...

Description

November 24th excess discharge and the intrusion of salt water pumping lowers the pressure of the freshwater, allowing the saltwater margin to move inland this movement creates both a cone of depression.. and an inverted cone of depression that brings salty water into the well. a well that formerly pumped fresh water now pumps salty water Speed of groundwater flows: permeability and water table gradient (slope) hydraulic gradient: ratio between the elevation difference and the flow distance (h/l)

Darcy's law Q = A (K ×h/l) the volume of water flowing in a certain time (Q) is proportional to the cross-sectional area of the aquifer through which the volume of water flows (A), the hydraulic conductivity (K) and the hydraulic gradient (h) Hydraulic conductivities vary among different materials: clay = 0.001

Erosion by Groundwater Features: • Caves and caverns ◦ Stalactites and stalagmites • Karst features (karst topography) ◦ Sinkholes characteristics of areas with karst • High rainfall and abundant vegetation • limestone bedrock with joints • significant hydraulic gradient Water Quality Lead pollution: industrial process that releases lead into the atmosphere -> rain Radioactive wastes: buried; leaches into aquifers Micro-organisms in water: residential septic tanks Other chemical contaminants: chlorinated solvents, mercury, road salt, pesticides, herbicides Human Contamination: home use, industrial chemicals, landfill dump, pumping wells Hydrology and Climate Warms areas with frequent rain = abundant water Warm arid/semiarid regions = rare rain & less water Icy climates = meltwaters from snow and ice Alternating seasons of dry and wet (monsoons) = changing water supplies Key climate factors: • relative humidity; amount of water vapour in the air, expressed as a % of total amount of water the air could hold at that temperature if saturated • warm air can hold more water vapour than cold air

• rainfall, when unsaturated warm air at a given relative humidity cools enough it becomes supersaturated and some of the vapour condenses into water droplets...