Drainage Basin
Human Effects on Cycle
- Changes in flow & storage (dams) - Irrigation and land drainage - Large scale abstraction
Decreased Evaporation
- Cold calm conditions - Polar climates
Outputs
- EVT - Runoff - Leakage
Groundwater Losses
- EVT (esp. low lying areas where water table close to surface) - Natural flow by spring & seepage into surface water bodies. - Leakage & outflow through aquicludes & into adjacent aquifers. - Artificial abstraction
Interception Factors
- Grasses = less interception due to smaller area - Agri crops = More crop density, high interception
Groundwater Recharge
- Infiltration of part of precipitation - Seepage through banks and beds of surface water bodies. - Inflow from adjacent rocks & aquifers - Artificial from irrigation, reservoirs etc.
Interception Types
- Interception Loss - Throughfall - Stemflow
Factors affecting Evaporation
- Meteorological (most important) - Humidity - Wind Speed - Amt. of water available - Vegetation Cover - Albedo of surface
Inputs
- Precipitation
Precipitation Types
- Rainfall - Snow - Frost - Hail - Dew
Factors Affecting Infiltration
- Rainfall duration - Antecedent soil moisture - Soil porosity - Vegetation cover - Raindrop size - Slope angle
Precipitation Factors affecting Hydrology
- Total amount - Intensity - Type - Geographic distribution - Variability
Water Storage Stages
- Vegetation - Surface - Soil Moisture - Groundwater - Water Channels
Increased Evaporation
- Warm Dry Weather - Arid/Semi-Arid Climates
Open System
Allows movement of energy and matter across its boundaries.
Field Capacity
Amount of water held in soil after excess water drains away.
Drainage Basin
Area of land drained by a river and its tributaries, including surface runoff and water table.
Throughflow
Lateral unsaturated flow of water in soil. Water flowing through soil in natural pipes and percolines.
Percolines
Lines of concentrated water flow between soil horizons.
Infiltration Capacity
Max. rate at which rain can be absorbed by soil in a given condition.
Aquifer Benefit
Natural regulator in hydrological cycle, absorbing water which would otherwise reach streams rapidly.
Baseflow
Part of a river's discharge provided by groundwater seeping into river bed.
Phreatic Zone
Permanently saturated zone within solid rocks and sediments. Upper layer is water table.
Evaporation
Process by which liquid/solid is changed into a gas Conversion of solid/liquid precipitation into water vapour in atmosphere
Infiltration
Process by which water soaks into or is absorbed by soil. Inversely related to overland runoff
Transpiration
Process by which water vapour escapes a living plant into the atmosphere
Abstraction
Process of removing water from a source
Wilting Point
Range of moisture content in which limit to plant growth occurs.
Recharge
Refilling of water in pores where water has dried up or been extracted by human activity.
Aquifers
Rocks that contain significant quantities of water.
Aeration Zone
Seasonally wetted/dried zone.
Groundwater
Sub surface water
Water Table
The level below which the ground is permanently saturated with water.
Throughfall
Water falling through vegetation gaps or dropping from leaves and twigs
Springs
Water flow reaching the surface.
Potential EVT
Water loss that would occur if there was an unlimited supply of water in the soil for use by vegetation.
Percolation
Water moving slowly downwards from soil to bedrock
Interception Loss
Water retained by plant surface which is either evaporated or absorbed
Overland Flow
Water that flow's over the land's surface.
Interception
Water that is caught & stored by vegetation
Stemflow
Water trickling down twigs/branches then down stem/trunk
Evapotranspiration
Combination of Evaporation & Transpiration Most important aspect of water loss
Precipitation
Conversion and transfer of moisture in atmosphere to land.
Hydrological Cycle
Cycle of water between atmosphere, lithosphere & biosphere.
