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## ANSQUICK >## Radius of influence |

This dialog window calculates the radius of influence for a pumping test or a slug test. Radius of influence is determined either from drawdowns in two wells or hydraulic diffusivity and time since the start of pumping.

The window is opened by "File > Hydrogeologist workbench > Radius of influence".

"Wells" tab of "Radius of influence" dialog box: calculation of radius of influence based on drawdown in two observation wells.

Explanatory table for tab "Wells"

Estimation of radius of influence based on drawdown in two observation wells in an infinite aquifer

"R, m" text box |
Information field to display the estimated radius of influence |

"Confined", "Unconfined", "Confined-unconfined" option |
Selection of aquifer type |

"s1, m" and "s2, m" text box |
Drawdown in the first and the second observation wells |

"r1, m" and "r2, m" text box |
Distances from the pumping well to the first and the second observation well |

"m, m" text box |
Thickness of a confined aquifer or initial saturated thickness of an unconfined aquifer |

"H, m" text box |
Initial Hydraulic Head that is measured from the aquifer bottom. This field is required only for confined-unconfined aquifers |

For different aquifer types, the following analytical solutions are applied:

а) confined aquifer

б) unconfined aquifer

в) confined-unconfined aquifer

"Time" tab of "Radius of influence" dialog box: calculation of radius of influence based on hydraulic diffusivity and time from start pumping.

Explanatory table for tab "Time"

Estimation of radius of influence based on hydraulic diffusivity and time from start pumping in an infinite aquifer

"t, day" text box |
Time from the start of pumping, days |

"a, m2/day" text box |
Hydraulic diffusivity for confined or unconfined aquifers , m2/day. After entering this value, Storage coefficient is recalculated |

"T, m2/day" text box |
Transmissivity of aquifer (auxiliary field). After entering this value, the hydraulic diffusivity is recalculated |

"S, –" text box |
Specific yield or Storage coefficient (auxiliary field). After entering this value, the hydraulic diffusivity is recalculated |

"Rq, m" text box |
Information field to display the calculated zone of quasi-steady state regime, m After entering a value in this field, the time when quasi-steady state condition begin at distance r from the pumping well is calculated. This time is automatically input in added to the text box "t, days" |

"R, m" text box |
Information field to display the calculated radius of influence, m |

"Slug test" tab of "Radius of influence" dialog box: calculation of radius of influence for slug tests

Explanatory table for tab "Slug test"

Estimation of radius of influence during slug test in an infinite aquifer

"R, m" text box |
Information field to display the calculated radius of influence, m |

"t (max), min" text box |
Information fields to display the time when the maximum radius of influence occurs, minutes |

"t, min" text box |
Time from start of test, minutes |

"k, m/day" text box |
Hydraulic conductivity of aquifer, m/day. After entering this value, transmissivity is recalculated. |

"S, –" text box |
Specific Yield or Storage Coefficient of aquifer (dimensionless). After entering this value, hydraulic diffusivity is recalculated. |

"m, m/day" text box |
Thickness of aquifer, m. After entering this value, transmissivity is recalculated. |

"rw, m" text box |
Screen radius of the pumping well |

"rc, m" text box |
Casing radius of the pumping well |

"Accuracy" frame |
Required accuracy of radius of influence: 1, 5 or 10% |

"T, m^2/day" text box |
Transmissivity of aquifer (auxiliary field). After entering this value, hydraulic diffusivity is recalculated |

"a, m^2/day" text box |
Hydraulic diffusivity (auxiliary field). After entering this value, Storage coefficient is recalculated |

"Ss, 1/m" text box |
Specific Storage (auxiliary field). After entering this value, Storage Coefficient is recalculated |

References

Справочное руководство гидрогеолога. Под ред. В.М. Максимова. Л.: Гостоптехиздат. 1959.

Guyonnet D., Mishra S., Mccord J. Evaluating the volume of porous medium investigated during slug tests // Ground Water. 1993. Vol. 31, N 4. P. 627–633.