ABSTRACT: Comparison is common in water management research: every table, map, and graph invites comparisons of different places and variables. Detailed international comparisons, however, seem infrequent in water resources research. To assess this perceived gap, this paper searched for examples of comparative research between two water sub-sectors in two countries using systematic bibliographic mapping procedures. It focused on rural and urban water conservation research in India and the United States. Search methods built upon procedures initially developed for the FAO Investment Centre and more advanced systematic review methods. The search generally confirmed that there have been few detailed comparative international studies on the subject of this review. Not surprisingly, there are a greater number of comparative studies between rural and urban water conservation within each country. The search also identified different conservation emphases in the two countries, e.g., rainwater harvesting in India compared with stormwater quality management in the United States. It identified unanticipated publications and l¬ines of comparative water conservation (e.g. comparative physiology). Some transnational research goes beyond comparison to address the diffusion of innovations, i.e. research linkages as well as comparisons, although these studies are also few. The more prevalent pattern involves parallel literatures, which indicate substantial opportunities for future comparative and transnational research. This review also identified diffusion of international knowledge paths that are not the product of formal comparative research. The final section focuses on the prospects and priorities for future international and inter-sectoral research, e.g. paired multi-objective river basin research, linkages between climate change adaptation and disaster risk reduction, diffusion of water conservation innovations, and synthesis of research on urban and rural rainwater harvesting in different countries.
KEYWORDS: comparative research, water conservation, bibliographic mapping, India, United States