Drainage water salinity of tubewells and pipe drains: A case study from Pakistan

Drainage water salinity data from 71 public deep tubewells and 79 pipe drainage units near Faisalabad, Pakistan, were studied. Drainage water salinity of the tubewells and the pipe drains remained approximately constant with time. This was attributed to the deep, highly conductive, unconfined aquifer underlying the area, which facilitates lateral groundwater inflow into the drained areas. Tubewells alongside surface drains showed average electrical conductivity, sodium adsorption ratio, and residual sodium carbonate values of 3.2 dS m(-1), 17.2 (meq 1(-1))(0.5), and 6.4 meg 1(-1), respectively. For pipe drains, which an situated in areas with comparable conditions, the corresponding values were 2.5 dS m(-1), 12.2 (meq1(-1))(0.5), and 3.7 meq 1(-1), respectively. Tubewells have an inferior drainage water quality because they attract water from greater depths, where the water is mon saline. (C) 1998 Elsevier Science B.V.