Stream Depletion Factors

There is usually a time lag between the start of groundwater pumping and when the rate of stream depletion reaches equilibrium. This is impacted by the hydraulic conductivity Hydraulic conductivity is a measure of how easily water can pass through soil or rock: high values indicate water can pass easily; low values indicate that the material is less permeable. of the aquifer and the distance between the well and the stream. The longer the distance of a pumping well from a stream, the longer the lag time will be. Lower hydraulic conductivity of an aquifer means a longer time lag.

The effects of groundwater pumping on surface water take time to occur. The flow and storage of water in a groundwater system strongly depend on the aquifer'sAn aquifer is the area saturated with water beneath the water table. hydraulic properties, such as the hydraulic conductivity. Initially, the effects of groundwater pumping are seen as changes in the nearby aquifer groundwater level. However, as time goes on, in areas where groundwater and surface water are hydrologically connected, hydrologically connected means the interconnection of groundwater and surface water such that they constitute one water supply and use of either results in an impact to both. the relative effect to streamflow increases. Generally, the farther a well is from a stream, the longer the lag time between pumping and observed depletions to streamflow. To compare depletions between locations, water managers use a stream depletions factor (SDF), which is the proportion of streamflow depletions relative to total groundwater pumping in a given length of time.

Percentage of groundwater pumping

100

Pumping Time (years)

Sources of pumped groundwater

Far Well Simulation (Current)

Streamflow depletion

Aquifer storage

Near Well Simulation (Compared)

Streamflow depletion

Aquifer storage

Hydrologic connection is the capacity a specific location has to impact another location through groundwater interactions. The Nebraska Department of Natural Resources (NeDNR) uses the stream depletions factor (SDF) A stream depletions factor (SDF) is the proportion of streamflow depletions relative to total groundwater pumping in a given length of time calculation to evaluate hydrologic connectivity. NeDNR considers the area in which pumping a well for 50 years would deplete streamflow by at least 10% of the total amount pumped, or an SDF of at least 10% after 50 years, to be the “Hydrologically Connected” or “10/50 Area”.

Tutorial

Adjust the location of the pumping well

Adjust the location of the pumping well using this slider or by clicking on the slider's labels.

The well can be placed at three different distances from the stream.

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