Managing Irrigation Systems

Although technical solutions are available, the root causes of these economic, social, and environmental problems are bad irrigation design and poor maintenance and management. Irrigation, if it is to be effective, has to be reliable; otherwise much or all of the potential benefit will be lost. Reliability depends, in turn, on an efficient and responsive organization, and the question here is whether this can best be supplied under central government or local control. Many ancient irrigation systems, for example, in Mesopotamia, Sri Lanka, and China, relied on central government control. But other irrigation systems, such as the subaks in Bali established over a thousand years ago, are much smaller (about 200 ha), are built and operated by the local community, and have social and religious significance. Communal systems tend to be highly responsive because the supply and regulation of the water are an integral part of the traditional practices of resource management in the community.

Often the answer lies in creating a good partnership between government and local communities. For centuries, in the valleys of northern Thailand, for example, community-maintained dams constructed of stone and wood have been linked to irrigation systems governed by representative bodies known as muang. When, in the 1960s and 1970s, the government constructed large-scale diversion systems designed to provide year-round irrigation, in many places it grafted them onto the local systems. During our Agroecosystem Analysis of the Chiang Mai Valley (see Chapter 11), we discovered that triple-cropping was being practiced only in the areas of these joint systems where the water supply was reliable enough to risk planting the high- value third season crops.³²