page_title: Well drainage
section_title: Flow to wells
hierarchical_section_title: Well drainage / Flow to wells
caption_attribution_description: Drainage by fully penetrating wells in a simple aquifer
context_page_description: Well drainage means drainage of agricultural lands by wells. Agricultural land is drained by pumped wells to improve the soils by controlling water table levels and soil salinity.
context_section_description: The basic, steady state, equation for flow to fully penetrating wells (i.e. wells reaching the impermeable base) in a regularly spaced well field in a uniform unconfined (preactic) aquifer with a hydraulic conductivity that is isotropic is:
  where Q = safe well discharge - i.e. the steady state discharge at which no overdraught or groundwater depletion occurs - (m³/day), K = uniform hydraulic conductivity of the soil (m/day), D = depth below soil surface,  = depth of the bottom of the well equal to the depth of the impermeable base (m),  = depth of the watertable midway between the wells (m),  is the depth of the water level inside the well (m),  = radius of influence of the well (m) and  is the radius of the well (m).
  The radius of influence of the wells depends on the pattern of the well field, which may be triangular, square, or rectangular. It can be found as:
  where  = total surface area of the well field (m²)and N = number of wells in the well field.
  The safe well discharge (Q) can also be found from:
  where q is the safe yield or drainable surplus of the aquifer (m/day) and  is the operation intensity of the wells (hours/24 per day). Thus the basic equation can also be written as:
caption: Geometry of a fully penetrating well drainage system in a uniform, isotropic aquifer
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