1. Sr. Irrig. Engr., International Water Management Institute (IWMI), 12 KM Multan Rd., Chowk Thoker Niaz Beg, Lahore, 53700, Pakistan (corresponding author). E-mail: a.sarwar@cgiar.org
2. Hydro. and Remore Sensing Specialist, International Water Management Institute (IWMI), P.O. Box 2075, Colombo, Sri Lanka. E-mail: wimbastiaanssen@compuserve.com