chapter 8: surface water resources

actual evapotranspiration

the actual amount of evaporation and transpiration occurring at any given location

aquifer

a subsurface body of permeable oak or sediments through which water can flow in amounts adequate for wells and springs

artesian

pressurized groundwater that rises in a well or rock structure above local water table; may flow out onto the ground without pumping

baseflow

the portion of streamflow that consists of groundwater

cone of depression

the depressed shape of the water table around a well. after active pumping. the water table adjacent to the well is drawn down by the water removal

deficit

in the water balance, the amount of expected evapotranspiration exceeds the actual amount

drainage basin

the basic spatial geomorphic unit of a river system; distinguished from a neighboring basin by ridges and highlands that form divides, marking the limits of the catchment area

drawdown

the water table getting over because too much water is being pumped out

evaporation

the movement of free water molecules away from a wet surface into air that is less than saturated. the phase change from water to water vapor

gaining stream

a stream where groundwater flows into a stream. common in humid environments

groundwater mining

pumping out water from aquifers

hydrologic cycle

a simplified model to show the flow of water, ice, and water vapor from place to place. this model is powered by solar energy and gravity

infiltration

water access to subsurface regions of soil moisture storage through penetration of the soil surface

losing stream

a stream that is not connected to groundwater and gradually loses water

lysimeter

a device that measures the total water inputs and outputs by measuring a change in weight over time

percolation

the process by which water permeates the soil or porous rock into the subsurface environment

permeability

the ability of water to flow through soil or rock, a function of the texture and structure of the medium

porosity

the spaces, or voids, between particles in a material such as soil or rock

potential evapotranspiration

the amount of moisture that would evaporate and transpire under optimum moisture conditions.

precipitation

the moisture supply in the water balance. takes the form of rain, snow, sleet, and hail

recharge

the process of water moving downward to replenish groundwater reservoirs

renewable resource

a resource that can continue to exist despite being consumed. they replenish themselves at the same rate they are drained

saturated zone

the zone in which all pores and rock features are filled with water

subsidence

occurs when the ground sinks due to the removal of groundwater

surplus

in the water balance, it is the condition that occurs when all water demands are met and extra water remains, often in the form of runoff that recharges lakes and groundwater

transpiration

the movement of water vapor out through pores in leaves; the water is drawn by the plant roots from soil moisture storage

unsaturated zone

the portion of the subsurface above the water table

water balance

a water accounting system for an area of earths surface using inputs of precipitation and outputs of evapotranspiration and surface runoff

water table

the upper surface of groundwater; that contact point between the zone of saturation and the zone of aeration in an unconfined aquifer

wetland

an area that is permanently or seasonally saturated with water and characterized by vegetation adapted to hydrocarbons soils