The interactive effects of wells refers to the withdrawal of groundwater from one well resulting in a reduction in water level in another, accidentally connected, well. Among several wells the cumulative interference may be complex. Well interference poses serious threats to sustainability and equity in well irrigation. This paper provides a combination of statistical and PRA approaches for selecting farmers to study and analyse the equity issues involved. The statistical approach provides the method for sampling study sites, and PRA is used for selecting farmers in the study sites. The justifications for this combined method is explained. PRA mapping is used for collecting data on year of well-drilling, inter-well distance, depth of wells, water yield and other variables which contribute to interference. An example is given from a village in Karnataka, India. Local water diviners and farmers were used as key informants in interviews and as participants in mapping exercises. Mapping was found to be useful in identifying other features which affect interference, and in analysing what different categories of farmer do when there is well failure. The next stage (studying coping mechanisms and addressing equity issues) are not discussed in detail here.
This paper may be of interest to those involved in irrigation and water -supply projects.