Hydrogeology and Environmental Geology
Hydrogeology and Environmental Geology tests groundwater occurrence and movement, aquifer properties, water quality and human impacts. Karnataka's hard-rock terrain makes this domain practical: borewells in granite and schist, fluoride and nitrate problems, and watershed management.
Core rules
- Porosity is the proportion of void space; permeability is the ability to transmit water. High porosity does not guarantee high permeability.
- An unconfined aquifer has a water table; a confined aquifer is bounded by impermeable layers and has a potentiometric surface.
- Recharge adds water to an aquifer; discharge removes it through springs, wells, rivers or evapotranspiration.
- Darcy's law: Q = K i A, where Q is discharge, K hydraulic conductivity, i hydraulic gradient and A cross-sectional area.
- Hard-rock aquifers in Karnataka store water mainly in fractures and weathered zones, so yields are limited and variable.
Worked example
An aquifer has K = 5 m/day, hydraulic gradient i = 0.002 and cross-sectional area A = 100 m². Calculate Q. Reasoning: Q = K i A = 5 × 0.002 × 100 = 1 m³/day. The low gradient gives a small flow despite a moderate K.
Traps
- Do not mix porosity and permeability.
- Keep units consistent; K in m/day and A in m² gives Q in m³/day.
- A confined aquifer's potentiometric surface is not the water table.
- Fluoride in Karnataka groundwater is geogenic in some granitic terrains, not simply pollution.
Karnataka link
Over-extraction, borewell density and poor recharge affect hard-rock aquifers; Western Ghats watersheds provide important recharge.