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 wate r salinity of the tubewells and the pipe drains remained approximately constant with time. This was attributed to the deep, highly conductiv e, unconfined aquifer underlying the area, which facilitates lateral g roundwater 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 si tuated in areas with comparable conditions, the corresponding values w ere 2.5 dS m(-1), 12.2 (meq1(-1))(0.5), and 3.7 meq 1(-1), respectivel y. Tubewells have an inferior drainage water quality because they attr act water from greater depths, where the water is mon saline. (C) 1998 Elsevier Science B.V.