In the arid and semiarid regions which comprise 50% of the world's arable land, water is the critical input on which food production increases depend. This manual discusses processes (of interest to planners) and techniques (of use to engineers, economists, and sociologists) to improve the efficiency of tertiary irrigation conveyance systems (ditches, laterals, and other small watercourses) which convey water from large canals to individual farms. Although the procedures outlined in the manual were developed on the basis of conditions in Pakistan, they are applicable where similar conditions obtain. The manual suggests the following procedure. (1) Analyze the extent and causes (e.g., permeable soils, poor maintenance, excess water supply) of channel losses and evaluate channel improvements in terms of the lost water's value to other users and its marginal value to crop production. (2) Develop specific remedies (including physical changes to the channels and conveyance system or changes in operation and management), test them under controlled conditions, and cost them realistically. (3) Package successful techniques, test these on a larger scale, and adjust the package as practical constraints arise. (4) Test the final version of the package in a full-scale pilot project. (5) Study local social and organizational structures and, where necessary, work to make these local structures receptive to new guidelines and policies regarding channel improvement, utilization, and maintenance. (6) Finally, apply the successful improvement package to the entire target area. The authors note in conclusion that despite any channel improvements, it is afterwards, when the channels must be maintained and the supplemental water put to good use, that the most difficult part of the process begins. A 30-item bibliography (1947-80), sample data collection sheets, and information on field, watercourse, and topographic mapping, differential leveling, channel design, choice of cross-sectional shapes, allocation of alternative improvement techniques, and overviews of two Pakistani training programs are appended.