Flows & Underground Water

🌿 Above Ground Flows

  1. What is throughfall?
    Throughfall occurs when leaves and twigs become saturated, causing water to drip from them. Precipitation can also fall directly through gaps in vegetation cover.

  2. What is stemflow?
    Stemflow is the movement of intercepted precipitation down the branches and main trunk of vegetation.

  3. What is overland flow?
    Overland flow happens when soil is saturated, or precipitation exceeds the infiltration rate, causing water to flow over the surface as runoff.

  4. What is Hortonian flow?
    Hortonian flow is shallow, fast-moving water that occurs when precipitation exceeds both the infiltration and depression storage capacity. It can cause severe soil erosion.

  5. What is channel flow?
    Channel flow is the movement of water in defined channels, such as streams and rivers.

🌱 Below Ground Flows

  1. What is infiltration?
    Infiltration is the process by which precipitation soaks into or is absorbed by the soil.

  2. What is infiltration capacity?
    Infiltration capacity is the maximum rate at which soil can absorb precipitation under specific conditions.

  3. What factors affect infiltration?
    Infiltration depends on rainfall duration, antecedent soil moisture, soil porosity, slope angle, and vegetation cover.

  4. What is percolation?
    Percolation is the slow downward movement of water from the soil into bedrock under gravity. It occurs quickly in Carboniferous limestone.

  5. What affects the rate of percolation?
    Percolation rate depends on the permeability and porosity of bedrock. Chalk and sandstone are porous, allowing water to pass through.

  6. What is throughflow?
    Throughflow is the movement of water through soil via natural pipes and percolines, occurring above the bedrock.

  7. What is groundwater?
    Groundwater is water that has infiltrated the ground and entered the phreatic zone, eventually discharging into channels.

  8. What is the phreatic zone?
    The phreatic zone is the part of an aquifer below the water table where all pores are permanently saturated.

  9. What is baseflow?
    Baseflow is the slow movement of groundwater into riverbeds, contributing to river discharge. It can take months or years to transfer.

🌊 Underground Water

  1. What is the water table?
    The water table is the upper layer of the phreatic zone. It rises and falls based on rainfall infiltration and baseflow from lower rocks.

  2. What is the aeration zone?
    The aeration zone lies above the water table and is seasonally wetted and dried, depending on rainfall.

  3. What causes groundwater recharge?
    Groundwater recharge occurs through:

    • Infiltration from precipitation

    • Seepage from riverbanks, lakes, and puddles

    • Leakage and inflow from adjacent rocks and aquifers

    • Artificial sources like irrigation and reservoirs

  4. What causes groundwater loss?
    Groundwater is lost through:

    • Evapotranspiration (especially in low areas)

    • Natural discharge (seepage and spring flow)

    • Leakage into aquicludes

    • Artificial abstraction

  5. What are aquifers?
    Aquifers are permeable rocks, like sandstone, limestone, and chalk, that hold significant amounts of water. They slowly release or absorb water to maintain streamflow during wet and dry periods.

  6. What are springs?
    Springs form when water reaches the surface after percolating through the ground. They often occur where water meets an impermeable layer or reaches the saturated zone.

🧮 Water Budget Equation

  1. What is the water budget equation?
    The water budget equation is:
    S = P - Q - E
    Where:

    • S = Soil Storage

    • P = Precipitation

    • Q = Channel Flow

    • E = Evapotranspiration